Inorganic Chemistry Flashcards
Atomic mass
= sum of masses of protons and neutrons
Isotopes
Different number of neutrons (i.e. same element with a different atomic mass)
Atomic weight
The weighted average of the naturally occurring isotopes of an element
Planck relation (frequency) (E)
= h f
Angular momentum of an electron (Bohr model) (L)
= (n h) / (2 pi)
Energy of an electron (Bohr model) (E)
= - Rh / n^2
Planck relation (wavelength) (E)
= h c / lambda
Energy of electron transition (Bohr model) (E)
= - Rh ( 1 / n0^2 - 1 / n^2)
Maximum number of electrons within a shell
= 2 n^2
Maximum number of electrons within a sub-shell
= 4 l + 2
Mass of proton
1 amu
Mass of neutron
1 amu
Atomic number
The number of protons
Mass number
The number of protons and neutrons
The isotopes of hydrogen
Protium, deuterium, tritium
Quantum
The energy difference between energy levels
Quantization
There is not an infinite range of energy levels available to an electron; electrons can exist only at certain energy levels
Does the energy level of an electron increase or decrease when it is farther from the nucleus?
Increase
Heisenberg uncertainty principle
It is impossible to know both an electrons position and its momentum exactly at the same time
Quantum numbers
Describe an electron in an atom
What are the quantum numbers?
Principal quantum number (n), azimuthal quantum number (l), magnetic quantum number (ml), spin quantum number (ms)
Principal quantum number (n)
Describes the average energy of a shell
Azimuthal quantum number (l)
Describes the subshells within a given principal energy level (s, p, d and f)
must be < n - 1
Magnetic quantum number (ml)
Specifies the particular orbital within a sub-shell where an electron is likely to be found at a given moment in time
must be between - l and + l
Spin quantum number (ms)
Indicates the spin orientation (+/- 1/2) of an electron in an orbital
n + l rule
Electrons fill the principal energy levels and subshells according to increasing energy
Hund’s rule
Sub-shells with multiple orbitals (p, d and f) fill electrons so that every orbital in a sub-shell gets one electron before any of them gets a second
Paramagnetic materials
Have unpaired electrons that align with magnetic fields, attracting the material to a magnet
Diamagnetic materials
Have all paired electrons, which cannot easily be realigned; they are repelled by magnets
Where are the valence electrons in representative elements (Groups 1, 2, 13 to 18)?
s and p orbitals
Where are the valence electrons in transition elements?
s and either d or f orbitals
Effective nuclear charge (Zeff)
The strength with which protons in the nucleus can pull on electrons
In which direction does Zeff increase on the periodic table?
Left to right
What happens to valence electrons as the principal energy level, n, increases from top to bottom in a group?
They become increasingly separated from the nucleus
In which direction does the principal energy level, n, increase on the periodic table?
Top to bottom
In which direction does the atomic number increase on the periodic table?
Left to right and top to bottom
Ionic radius
The size of charged species
Are cations smaller or larger than their corresponding neutral atom?
Smaller
Are anions smaller or larger than their corresponding neural atom?
Larger
Ionization energy
The amount of energy necessary to remove an electron from the valence shell of a gaseous species
In which direction does ionization energy increase on the periodic table?
Left to right and bottom to top
Electron affinity
The amount of energy released when a gaseous species gains an electron in its valence shell
In which direction does electron affinity increase on the periodic table?
Left to right and bottom to top
Electronegativity
A measure of the attractive force of the nucleus for electrons within a bond
In which direction does electronegativity increase on the periodic table?
Left to right and bottom to top
What is the oxidation state of alkali metals?
+1
Do alkali metals prefer to gain or lose electrons?
Lose
Which metals are the most reactive on the periodic table?
Alkali metals and alkaline earth metals
What is the oxidation state of alkaline earth metals?
+2
Do alkaline earth metals prefer to gain or lose electrons?
Lose
What is the oxidation state of chalcogens?
-2 or +6 (depending on whether they are non-metals or metals, respectively)
What is the oxidation state of halogens?
-1
Do halogens prefer to gain or lose electrons?
Gain
Which group has the highest electronegativity on the periodic table?
Halogens
Noble gases
Have fully filled valence shell in their standard state and prefer not to give up or take on additional electrons
They have very high ionization energies and virtually nonexistent electronegativities and electron affinities
Transition metal features
Take on multiple oxidation states
Can form hydration complexes with water, increasing their solubility in water
Elements that form incomplete octets
H, He, Li, Be, B
Elements that form expanded octets
Any element in period 3 or greater
Characteristics of ionic bonds
- High melting and boiling points due to electrostatic attractions
- Solubility of ions in water and other polar solvents due to interactions with polar solvents
- Good conductors of heat and electricity
- Have crystal lattice arrangements to minimize repulsive forces
- Large electronegativity differences between ions (delta EN > 1.7)
What is bond strength defined by?
The electrostatic attraction between nuclei and electrons
Do multiple bonds (higher bond order) increase or decrease bond strength?
Increase
Does a longer bond length result in a stronger bond or a weaker bond?
Weaker bond
Bond energy
The minimum amount of energy needed to break a bond
Does a stronger bond have higher bond energy or lower bond energy?
Higher
delta EN in non-polar covalent bonds
= between 0 and 0.5
delta EN in polar covalent bonds
= between 0.5 and 1.7
delta EN in ionic bonds
= 1.7 or higher
Intermolecular forces
Hydrogen bonding, dipole-dipole interactions and London dispersion forces
They are electrostatic attractions between molecules
They are weaker than covalent bonds (which are weaker than ionic bonds)
What is the strongest intermolecular force?
Hydrogen bonding
What is the weakest intermolecular force?
London dispersion forces
Dipole-dipole interactions
A dipole consists of a segment of a molecule with partial positive and partial negative regions. The positive need of one molecule is attracted to the negative end of another molecule, and vice-versa.
When does hydrogen bonding occur?
A molecule must have a hydrogen bonded to either N, O or F
Octet rule
Elements will be most stable with eight valence electrons
Bond order
Refers to whether a covalent bond is a single bond, double bond or triple bond
Where do non-polar covalent bonds form?
In molecules in which both arms have exactly the same electronegativity
When do polar covalent bonds form?
When there is a significant difference in electronegativity, but not enough to transfer electrons and form an ionic bond
When do coordinate covalent bonds form?
When a single atom provides both bonding electrons while the other atom does not contribute any
Common in Lewis acid-base chemistry
When do resonance structures appear?
When a molecule has a pi system of electrons
Represent all the possible configurations of electrons (stable and unstable) that contribute to the overall structure
Valence shell electron pair repulsion (VESPER) theory
Predicts the three-dimensional molecular geometry of covalently bonded molecules
Electrons arrange themselves to be as far apart as possible from each other in three-dimensional space
Do non-bonding electrons exert more or less repulsion on each other than bonding electrons?
More repulsion because they reside closer to the nucleus
Electronic geometry
Refers to the position of all electrons in a molecule, whether bonding or nonbonding
Molecular geometry
Refers to the position of only the bonding pairs of electrons in a molecule
What kind of bonds do polar molecules have?
Polar bonds
What kind of bonds do non-polar molecules have?
Polar bonds or non-polar bonds
What are sigma bonds results of?
The result of head-to-head overlap
What are pi bonds results of?
The result of the overlap of two parallel electron cloud densities
London dispersion forces
Present in all atoms and molecules
What happens to London dispersion forces when an atom or molecule’s size increases?
Increase
Where are dipole-dipole interactions most prominent?
Liquids and solids
Dipole moment (p)
= q d
q = charge d = distance between charges
Formal charge
= N valence electrons - N non-bonding - (1/2 N bonding)
Molarity (M)
= moles of solute / liters of solution (mol/L)
Used for rate laws, the law of mass action, osmotic pressure, pH and pOH and the Nernst equation
How are molecular formulas and empirical formulas similar?
Both contain the same elements in the same ratios
How are molecular formulas and empirical formulas different?
The molecular formula gives the actual number of atoms of each element in the compound
The empirical formula gives only the ratio and therefore may or may not give the actual number of atoms
Molecular formula
Gives the actual number of atoms of each element in the compound
Empirical formula
Gives only the ratio and therefore may or may not give the actual number of atoms
How to find the empirical formula when we only have the percent mass of the elements in the molecule?
- Assume the percentages are the total grams of each element (e.g. 40.9% C = 40.9 g C)
- Convert grams to moles (e.g. 40.9 g C = 3.4 mol C)
- Once that is done for all the compounds, divide all the moles by the smallest mole value obtained (e.g. C 3.4 mol C, 4.6 mol H, 3.4 mol O => 1 mol C, 1.33 mol H, 1 mol O)
- Multiply the mole values obtained by whole numbers, until all the mole values are whole numbers (e.g. multiply by 2 => 2 mol C, 2.66 mol H, 2 mol O // multiply by 3 => 3 mol C, 3.99 mol H [~ 4 mol H], 3 mol O)
Answer C3H4O3
How to find the empirical formula when both the percent mass of the elements in the molecule and the molar mass of the whole molecule are given?
- Multiply the molar mass by the percentages given to find the mass of each element present in 1 mole of the molecule (e.g. [40.9% C * molar mass of whole molecule] / 12 g/mol C = 9 mol)
- Divide all the mole values you get by the common denominator (e.g. 9 mol C, 12 mol H, 9 mol O => 3 mol C, 4 mol H, 3 mol O)
Answer C3H4O3
What happens when Zn(NO3)2 dissolves in (NH4)2S?
Ammonium swaps places with (or displace) zinc cations yielding ammonium nitrate and zinc (II) sulfide. Zinc (II) sulfide then precipitates out of solution as a solid salt.
2 H2 + O2 –>
2 H2O
What type of reaction is 2 H2 + O2 –> 2 H2O
Combination
Al(OH)3 + H3PO4 –>
3 H2O + AlPO4
What type of reaction is Al(OH)3 + H3PO4 –> 3 H2O + AlPO4
Neutralization (a type of double-displacement)
2 H2O –(electricity)–>
2 H2 + O2
What type of reaction is 2 H2O –(electricity)–> 2 H2 + O2
Decomposition
NaNO3 + CuOH –>
NaOH + CuNO3
What type of reaction is NaNO3 + CuOH –> NaOH + CuNO3
Double-displacement (metathesis)
Zn + AgCl –>
ZnCl + Ag
What type of reaction is Zn + AgCl –> ZnCl + Ag
Single-displacement
Is HCl an electrolyte or a non-electrolyte?
Electrolyte
Is sucrose an electrolyte or a non-electrolyte?
Non-electrolyte
Is MgBr2 an electrolyte or a non-electrolyte?
Electrolyte
Is CH4 an electrolyte or a non-electrolyte?
Non-electrolyte
Phosphate
PO4^3-
Hypochlorite
ClO-
Ammonium
NH4+
Phosphide
P^3-
Bicarbonate
HCO3-
Nitrite
NO2-
Chromium (II)
Cr^2+
Moles from mass
= mass of sample / molar mass
Gram equivalent weight (GEW)
= molar mass / n
A measure of the mass of a substance that can donate one equivalent of the species of interest
Equivalents from mass
= mass of compound / gram equivalent weight
Molarity from normality
= normality / n
Percent composition
= (mass of element in formula / molar mass) 100
Determine the mass of the individual element and divide by the molar mass of the compound
Percent yield
= (actual yield / theoretical yield) 100
Molecular weight
The mass (in amu) of the constituent atoms in a compound as indicated by the molecular formula
Molar mass
The mass of one mole of a compound (g/mol)
Avogadro’s number
6.022e23
Normality
The ratio of equivalents per liter
The molarity of the species of interest
= molarity * n
n = equivalents of H+ or OH-
Used for acid-base and oxidation-reduction reactions
How is normality related to molarity?
By multiplying the molarity by the number of equivalents present per mole of compound
Equivalents
Moles of the species of interest
Law of constant composition
Any pure sample of a compound will contain the same elements in the same mass ratio
Combination reaction
Occurs when two or more reactants combine to form one product
Decomposition reaction
Occurs when one reactant is chemically broken down into two or more products
Combustion reaction
Occurs when a fuel and an oxidant (typically oxygen) react, forming the products water and carbon dioxide (if the fuel is a hydrocarbon)
Displacement reaction
Occurs when one or more atoms or ions of one compound are replaced with one or more atoms or ions of another compound
Single-displacement reaction
Occurs when an ion of one compound is replaced with another element
Double-displacement reaction
Occurs when elements from two different compound trade places with each other to form two new compounds
Neutralization reaction
Occurs when an acid reacts with a base to form a salt and usually water
Limiting reagent
The reactant that will be consumed first in a chemical reaction
Theoretical yield
The amount of product generated if all of the limiting reactant is consumed with no side reactions
What are Roman numerals in ion nomenclature used for?
Non-representative elements to denote ionic charge
What is -ous in ion nomenclature used for?
Indicate lesser charge
What is -ic in ion nomenclature used for?
Indicate greater charge
What is -ide in ion nomenclature used for?
The ending of monatomic anions
Oxyanions suffixes
-ite and -ate
What is -ite in ion nomenclature used for?
Contain a lesser amount of oxygen
What is -ate in ion nomenclature used for?
Contain a greater amount of oxygen
Oxyanions prefixes
Hypo- and per-
What is hypo- in ion nomenclature used for?
Contain the fewest amount of oxygen
What is per- in ion nomenclature used for?
Contain the highest amount of oxygen
Hydrogen-donating polyatomic ions
Hydrogen/bi- and dihydrogen
What is hydrogen/bi- in ion nomenclature used for?
Polyatomic ion that donates one hydrogen
What is dihydrogen in ion nomenclature used for?
Polyatomic ion that donates two hydrogens
Electrolytes
Contain equivalents of ions from molecules that dissociate in solution
What determines the strength of an electrolyte?
Its degree of dissociation (i.e. solvation)
Ionic compounds
- They are composed of atoms held together by ionic bonds
- They associate charged particles with large differences in electronegativity
- Form large arrays of ions in crystalline solids
- Measured with formula weights
- Electrons are donated from the less electronegative atom to the more electronegative atom
Chalcogens
Group 16 elements
Do noble gases have high or low ionization energies?
Very high
Do noble gases have high or low electronegativities?
Virtually nonexistent
Do noble gases have high or low electron affinities?
Virtually nonexistent
Do ionic bonds have high or low melting points?
High
Do ionic bonds have high or low boiling points?
High
Why do ionic bonds have high melting and boiling points?
Due to their electrostatic attractions
Do ionic compounds interact with polar solvents?
Yes
Are ionic compound good conductors of heat and electricity?
Yes
How do ionic bonds minimize repulsive forces?
Because they have crystal lattice arrangements
Do ionic bonds have large electronegativity differences between ions?
Yes, EN > 1.7
Rate-determining step
The slowest step of a reaction
Determines the overall rate of the reaction because the reaction can only proceed as fast as the rate at which this step occurs
Activation energy
The minimum energy needed for a chemical reaction to occur
Transition state theory of chemical kinetics
States that molecules form a transition state or activated complex during a reaction in which the old bonds are partially dissociated and the new bonds are partially formed
Requires a certain activation energy to be overcome in order for a reaction to occur (therefore not all reactions will occur)
Focuses on forming a high-energy activated complex that can then proceed forward or backward, forming the products or reverting to the reactants, respectively
Collision theory of chemical kinetics
States that a reaction rate is proportional to the number of effective collisions between the reacting molecules
Requires a certain activation energy to be overcome in order for a reaction to occur (therefore not all reactions will occur)
Focuses on the energy and orientation of reactants, and considers each potential reaction to be “all-or-nothing” (either there is enough energy to form the products, to there is not).
What happens to a zero-order reaction if the temperature is lowered?
The reaction rate decreases
What happens to a first-order reaction if the temperature is lowered?
The reaction rate decreases
What happens to a second-order reaction if the temperature is lowered?
The reaction rate decreases
What happens to a zero-order reaction if all the reactants’ concentrations doubled?
The reaction rate is unaffected
What happens to a first-order reaction if all the reactants’ concentrations doubled?
The reaction rate is doubled
What happens to a second-order reaction if all the reactants’ concentrations doubled?
The reaction rate is quadrupled
What happens to a zero-order reaction if a catalyst was added?
The reaction rate increases
What happens to a first-order reaction if a catalyst was added?
The reaction rate increases
What happens to a second-order reaction if a catalyst was added?
The reaction rate increases
How to determine the rate law of a reaction?
- Compare two sets of data in which only one of the reactant’s concentration has changed
- Rate after concentration change / rate before concentration change = (rate of second concentration / rate of first concentration) ^ x
- Solve for x
Answer = x is the order of that reactant
Repeat for the rest of the reactants and then put it all in rate = k [A]^x [B]^y …
Gibbs free energy (delta G)
Determines whether or not a reaction is spontaneous
Is derived from both enthalpy and entropy values for a given system
Intermediates
Molecules that exist within the course of a reaction, but are neither reactants nor products overall
How can a collision be effective?
Molecules must be in the proper orientation and have sufficient kinetic energy to excel the activation energy
Arrhenius equation
k = A e^(-Er / [RT])
What is the highest point on a free energy reaction diagram?
Transition state
How does changing the medium affect the rate of a reaction?
It can increase or decrease the rate of the reaction, depending on how the reactants interact with the medium
Homogeneous catalysts
Are in the same phase as the reactants
Heterogenous catalysts
Are in a different phase from the reactions
Reaction rate
Measured in terms of the rate of disappearance of a reactant or appearance of a product
Rate law
rate = k [A]^x [B]^y
Do rate orders match stoichiometric coefficients?
Not necessarily
How are rate laws determined?
Through experimentation
Rate order
The sum of all individual rate orders in the rate law
Zero-order reactions
Have a constant rate that does not depend on the concentration of reactant
How can the rate of a zero-order reaction be affected?
Changing the temperature or adding a catalyst
What is the shape of a concentration v. time curve of a zero-order reaction?
Linear
What is the slope of a concentration v. time curve of a zero-order reaction?
-k
First-order reactions
Have a non constant rate that depends on the concentration of a reactant
What is the shape of a concentration v. time curve of a first-order reaction?
Nonlinear
What is the slope of a concentration v. time curve of a first-order reaction?
ln [A] v. time
slope = -k
What does a first-order reaction depend on?
Concentration of a reactant
Second-order reactions
Have a non constant rate that depends on the concentration of a reactant
What does a first-order reaction depend on?
Concentration of a reactant
What is the shape of a concentration v. time curve of a second-order reaction?
Nonlinear
What is the slope of a concentration v. time curve of a second-order reaction?
1/[A] v. time
Slope = k
Broken-order reactions
Reactions with nonifnteger orders
Mixed-order reactions
Reactions that have a rate order that changes over time
Collision theory equation
Rate = Z x f
Definition of rate
Rate = - (delta [A]) / (a delta t) = - (delta [B]) / (b delta t) = (delta [C]) / (c delta t) = (delta [D]) / (d delta t)
Radioactive decay [A]t
= [A]o e^(-k t)
Is a non-spontaneous reaction endergonic or exergonic?
Endergonic
Is an endergonic reaction reaction spontaneous?
No
Endergonic (non-spontaneous) reaction
The activation energy of the forward reaction is greater than the activation energy of the reverse reaction
The products have a higher free energy than the reactants
Are catalysts used up in a reaction?
No
How do catalysts increase the rate of the reaction?
By lowering the activation energy
Do catalysts alter the thermodynamics of the reaction?
No
What is the direction of the reaction when Q = Keq?
The reaction is at equilibrium, no net reaction
Q = Keq
Reaction is at dynamic equilibrium
What is the Gibbs free energy of a reaction when Q = Keq?
0
What is the direction of the reaction when Q > Keq?
Reaction proceeds towards the reactants
What is the Gibbs free energy of a reaction when Q > Keq?
Positive
What is the direction of the reaction when Q < Keq?
Reaction proceeds towards the products
What is the Gibbs free energy of a reaction when Q < Keq?
Negative
Kp
= Partial pressure of products in gas phase / Partial pressure of reactants in gas phase
Kc
= Concentration of products in aqueous phase / Concentration of reactants in aqueous phase
What conditions favor the formation of a kinetic product?
Low temperatures with low heat transfer
What conditions favor the formation of a thermodynamic product?
High temperatures with high heat transfer
On a reaction coordinate diagram, how would the kinetic pathway appear as compared to the thermodynamic pathway?
Kinetic pathways require a smaller gain in free energy to reach the transition state. They also have a higher free energy of the products, with a smaller difference in free energy between the transition state and the products.
Equilibrium constant (Keq)
= Concentrations of products / concentrations of reactants = ([C]^c [D]^d) / ([A]^a [B]^b)
Reaction quotient (Qc)
= Concentrations of products / concentrations of reactants = ([C]^c [D]^d) / ([A]^a [B]^b)
Reversible reactions
Eventually reach a state in which energy is minimized and entropy is maximized
Dynamic chemical equilibria
The reactions are still occurring, just at a constant rate
The concentrations of reactants and products remain constant because the rate of the forward reaction equals the rate of the reverse reaction
Why are the concentrations of reactants and products constant in dynamic chemical equilibria?
Because the rate of the forward reaction equals the rate of the reverse reaction
Law of mass action
Gives the expression for the equilibrium constant Keq
What is the difference between the reaction quotient (Q) and the equilibrium constant (Keq)?
They use the same formula, but the reaction quotient can be calculated at any concentrations of reactions and products (i.e. at any point in the reaction). The equilibrium constant can only be calculated at equilibrium.
Does the equilibrium constant (Keq) change when the temperature changes?
Yes
Do solids appear in the law of mass action?
No
Do liquids appear in the law of mass action?
No
Do gases appear in the law of mass action?
Yes
Do aqueous species appear in the law of mass action?
Yes
Le Châtelier’s principle
When a chemical system experiences a stress, it will react so as to restore equilibrium
Types of stresses applied to a system
Changes in concentration, pressure, volume and temperature
Will increasing the concentration of reactants shift the reaction to the right or to the left?
Right
Will decreasing the concentration of products shift the reaction to the right or to the left?
Right
Will increasing the concentration of products shift the reaction to the right or to the left?
Left
Will decreasing the concentration of reactants shift the reaction to the right or to the left?
Left
Will Increasing the pressure on a gaseous system increase or decrease its volume?
Decrease
Will increasing the pressure on a gaseous system (decreasing its volume) shift the reaction towards the side with the fewer moles of gas or the side of the more moles or gas?
Fewer
Will decreasing the pressure on a gaseous system increase or decrease its volume?
Increase
Will decreasing the pressure on a gaseous system (increasing its volume) shift the reaction towards the side with the fewer moles of gas or the side of the more moles or gas?
More
Will increasing the temperature of an endothermic reaction shift the reaction to the right or to the left?
Right
Will decreasing the temperature of an exothermic reaction shift the reaction to the right or to the left?
Right
Will decreasing the temperature of an endothermic reaction shift the reaction to the right or to the left?
Left
Will increasing the temperature of an exothermic reaction shift the reaction to the right or to the left?
Left
Kinetic products
Higher in free energy than thermodynamic products
Can form in lower temperatures
Form more quickly than thermodynamic products
Which product is higher in free energy: kinetic or thermodynamic?
Kinetic
Which product can form in low temperatures: kinetic or thermodynamic?
Kinetic
Which product can form faster: kinetic or thermodynamic?
Kinetic
Thermodynamic products
Lower in free energy than kinetic products
More stable than kinetic products
Slower in formation than kinetic products
More spontaneous than kinetic products
Have a more negative Gibbs free energy than kinetic products
Which product is lower in free energy: kinetic or thermodynamic?
Thermodynamic
Which product is more stable: kinetic or thermodynamic?
Thermodynamic
Which product forms slower: kinetic or thermodynamic?
Thermodynamic
Which product forms more spontaneously: kinetic or thermodynamic?
Thermodynamic
Which product has a more negative Gibbs free energy: kinetic or thermodynamic?
Thermodynamic
Does a reaction in equilibrium have equal forward and reverse reactions?
Yes
Kc»_space; 1
The equilibrium mixture will favor products over reactants
Ka
The ratio of products to reactants with each species raised to its stoichiometric coefficient
Ka > 10^-7
The compound contains more H+ than HA- at equilibrium, which makes it an acid
Keq of the reverse reaction
= (Keq of the forward reaction)^-1
Negative delta H
Exothermic reaction
A person snaps an ice pack and places it on his or her leg. In terms of energy transfer, what would be considered the system and what would be the surroundings in this scenario?
System: icepack
Surroundings: the person
Isothermal process
Temperature is constant
Adiabatic process
No heat is flowing into or out of the system
Isobaric process
Pressure is constant
Isovolumetric (isochoric)
Volume is constant
Delta U in an isothermal process
= 0
Q in an isothermal process
= W
W in an isothermal process
= Q
Q in an adiabatic process
= 0
Delta U in an adiabatic process
= - W
P-V graph in an isobaric process
Flat line
W in an isochoric process
= 0
Delta U in an isochoric process
= Q
Standard conditions
T = 25 C (298 K) P = 1 atm Concentration = 1 M
When are standard conditions used for calculation?
Kinetics, equilibrium and thermodynamics calculations use standard conditions
State function
Properties of a system at equilibrium
Independent of the path taken to achieve equilibrium
State functions may depend on one another
Process function
Define the path between equilibrium states
Common state functions
Pressure (P), density (p), temperature (T), volume (V), enthalpy (H), internal energy (U), Gibbs free energy (G) and entropy (S)
Triple point
The combination of temperature and pressure at which all three phases are in equilibrium
Critical point
The temperature and pressure above which liquid and gas phases are indistinguishable and the heat of vaporization is zero
Common process functions
Heat (Q) and work (W)
Temperature
Indirect measure of the thermal content of a system that looks at average kinetic energy of particles in a sample
Heat
The thermal energy transferred between objects as a result of differences in their temperatures
Specific heat
The energy required to raise the temperature of one gram of a substance by one degree Celsius
Heat capacity
The product of mass and specific heat and is the energy required to raise any given amount of a substance one degree Celsius
Constant-volume calorimetry (bomb calorimeter)
Heats of certain reactions (like combustion) can be measured indirectly by assessing temperature change in a water bath around the reaction vessel
Constant-pressure calorimetry (coffee cup calorimeter)
Exposed to constant (atmospheric) pressure. As the reaction proceeds, the temperature of the contents is measured to determine the heat of the reaction
What is the specific heat of water (in calories)?
1 cal / g dot K
Endothermic process
An increase in heat content of a system from the surroundings
Exothermic process
A release of heat content from a system
delta H in an endothermic process
Positive
delta H in an exothermic process
Negative
Enthalpy of a reaction
= bonds broken - bonds formed
Rank the phases of matter from lowest to highest entropy
Solids < liquids < gases
Entropy in terms of energy dispersal and disorder
Entropy increases as a system has more disorder or freedom of movements, and energy is dispersed in a spontaneous system
Entropy of the universe can never be decreased spontaneously
A measure of the degree to which energy has been spread throughout a system or between a system and its surrounds
A ratio of heat transferred per mole per unit kelvin
Liquid water –> solid water : increase or decrease in entropy?
Decrease (freezing)
Dry ice sublimates into carbon dioxide : increase or decrease in entropy?
Increase (sublimation)
NaCl (s) –> NaCl (aq) : increase or decrease in entropy?
Increase (dissolution)
N2 (g) + 3 H2 (g) –> 2 NH3 (g) : increase or decrease in entropy?
Decrease (fewer moles of gas)
An ice pack is placed on a wound : increase or decrease in entropy?
Increase (heat is transferred)
Gibbs free energy (delta G)
= delta H - T delta S
Gibbs free energy at equilibirum
= 0
First law of thermodynamics
delta U = Q - W
Heat transfer (no phase change) (q)
m c delta T
Heat transfer (duding phase change) (q)
m L
Generalized enthalpy of reaction (delta H reaction)
= H products - H reactants
Standard enthalpy of reaction (delta H reaction)
= sum of delta Hf, products - sum of delta Hf, reactants
Bond enthalpy (delta H reaction)
= sum of delta H bonds broken - sum of delta H bonds formed
= total energy absorbed - total energy released
Entropy (delta S)
= Q rev / T
Second law of thermodynamics
delta S universe = delta S system + delta S surroundings > 0
Standard entropy of reaction
delta S reaction = sum of delta Sf, products - sum of delta Sf, reactants
Standard Gibbs free energy of reaction (delta G reaction)
= sum of delta Gf, products - sum of delta Gf, reactants
Standard Gibbs free energy from equilibrium constant (delta G reaction)
= - R T ln (Keq)
Gibbs free energy from reaction quotient (delta G reaction)
= delta G reaction + R T ln (Q) = R T ln (Q / Keq)
Isolated systems
Exchange neither matter nor energy with the environment
Closed systems
Exchange energy, but not matter, with the environment
Open systems
Exchange both energy and matter with the environment
When do phase changes exist?
At characteristic temperatures and pressures
Where do fusion (melting) and freezing (crystallization or solidification) occur?
At the boundary between the solid and the liquid phases
Where do vaporization (evaporation or boiling) and condensation occur?
At the boundary between the liquid and the gas phases
Where do sublimation and deposition occur?
At the boundary between the solid and the gas phases
Phase diagram
Graphs the phases and phase equilibria as a function of temperature and pressure
Enthalpy
A measure of potential energy of a system found in intermolecular attractions and chemical bonds
Hess’s law
The total change in potential energy of a system is equal to the changes of potential energies of the individual steps of the process
When is entropy maximized?
At equilibrium
Negative delta G
Reaction proceeds in the forward direction (spontaneous)
Endothermic reaction (conclusion, not a comment)
Positive delta G
Reaction proceeds in the reverse direction (nonspontaneous)
Exothermic reaction (conclusion, not a comment)
Does Gibbs free energy depend on temperature?
Yes
Temperature-dependent processes
Change between spontaneous and nonspontaneous, depending on the temperature
What must be the value of Keq if ln (Keq) is positive?
Keq > 1
Combustion
Hydrocarbon reacting with oxygen to produce carbon dioxide and water
Do longer hydrocarbon chains yield greater or less amounts of combustion products?
Greater
Do longer hydrocarbon chains release more or less heat in a combustion process?
More
Spontaneous forward reaction
Keq > Q
Characteristics of gas phase
Compressible, have rapid molecular motion, have large intermolecular distances, have weak intermolecular forces
What will happen to the level of mercury in a mercury barometer if the barometer was moved to the top of a mountain?
Decreases
What will happen to the level of mercury in a mercury barometer if the barometer was placed ten meters under water?
Increases
Standard temperature and pressure (STP) conditions
T = 273 K (0 C)
P = 1 atm
One mole of ideal gas occupies 22.4 L
Standard conditions
T = 298 K (25 C) P = 1 atm Concentration = 1 M
How can the concentration of carbon dioxide in sodas or other carbonated beverages be so much higher than that of atmospheric carbon dioxide?
High pressures of carbon dioxide are forced on top of the liquid in sodas, increasing its concentration in the liquid.
Assumptions made by the kinetic molecular theory
Negligible volume of gas particles, no intermolecular forces (neither attraction nor repulsion), random motion, elastic collisions among gas particles, and the average kinetic energy of the gas particles is recruit proportional to temperature
Hydrogen sulfide (H2S) has a very strong rotten egg odor. Methyl salicylate (C8H8O) has a wintergreen odor, and benzaldehyde (C7H6O) has a pleasant almond odor. If the vapors for these three substances were released at the same time from across the room, in which order would one smell the orders?
The rotten egg odor first, the almond next and the wintergreen last. Because all of the gases have the same temperature, they have the same kinetic energy; thus, the lightest molecules travel the fastest.
In what ways do real gases differ from ideal gases?
Real gas molecules have nonnegligible volume and attractive forces. Real gases deviate from ideal gases at high pressure (low volume) and low temperature.
If the attractive forces between gas molecules were to increase while the actual volumes of the molecules remained negligible, what would occur?
According to the van der Waals equation, if a is increased while b remains negligible, the correction term (n^2 a) / V^2 gets larger, and the pressure or volume must drop to compensate
If the volumes of gas molecules were to increase while the attractive forces between the molecules remained negligible, what would occur?
Increasing the volume of gas molecules while keeping attraction negligible makes the term V - nb smaller; thus, the pressure or volume must rise to compensate
Ideal gas law
P V = n R T
Describes the relationship between the four variables of the gas state for an ideal gas
Density of a gas
p = m / V = (P M) / (R T)
Combined gas law
(P1 V1) / T1 = (P2 V2) / T2
A combination of Boyle’s, Charles’s and Gay-Lussac’s laws; it shows an inverse relationship between pressure and volume along with direct relationships between pressure and volume with temperature
Avogadro’s principle
n / V = k
n1 / V1 = n2 / V2
A special case of the ideal gas law for which the pressure and temperature are held constant; it shows a direct relationship between the number of moles of gas and volume
Boyle’s law
P V = k
P1 V1 = P2 V2
A special case of the ideal gas law for which temperature and the tumble of moles are held constant; it shows an increase relationship between pressure and volume
Charles’s law
V / T = k
V1 / T1 = V2 / T2
A special case of the ideal gas law for which pressure and number of moles are held constant; it shows a direct relationship between temperature and volume
Gay-Lussac’s law
P / T = k
P1 / T1 = P2 / T2
A special case of the ideal gas law for which volume and number of moles are held constant; it shows a direct relationship between temperature and pressure
Dalton’s law (total pressure from partial pressures) (PT)
= PA + PB + …
Dalton’s law (partial pressure from total pressure) (PA)
= XA PT
XA = moles of A / total number of moles
Henry’s law
[A] = kH x PA
[A1] / P1 = [A2] / P2 = kH
States that the amount of gas dissolved in solution is directly proportional to the partial pressure of that gas at the surface of a solution
Average kinetic energy of a gas (KE)
= 1/2 m v^2 = 1.5 kB T
Root-mean-square speed (u rms)
= square root of ([3 R T] / M)
Graham’s law
r1 / r2 = square root of (M2 / M1)
Describes the behavior of has diffusion or effusion, stating that gases with lower molar masses will diffuse or effuse faster than gases with higher molar masses at the same temperature
van der Waals equation of state
(P + [n^2 a] / v^2) (V - n b) = n R T
Is used to correct the ideal gas law for intermolecular attractions (a) and molecular volume (b)
What is the least dense phase of matter?
Gases
Do gases conform to the shape of the container?
Yes
Are gases easily compressible?
Yes
Variables that describe gas systems
Temperature, pressure, volume and moles
1 atm in mmHg
760
760 mmHg in atm
1
1 atm in torr
760
760 mmHg in torr
760
760 torr in mmHg
760
760 torr in atm
1
1 atm in Pa
101.325 kPa
760 mmHg in Pa
101.325 kPa
760 torr in Pa
101.325 kPa
101.325 kPa in torr
760
101.325 kPa in mmHg
760
101.325 kPa in atm
1
Simple mercury barometer
Measures incident (usually atmospheric) pressure. As pressure increases, more mercury is forced into the column, increasing its height. As pressure decreases, mercury glows out of the column under its own weight, decreasing its height.
Dalton’s law of partial pressures
States theta individual gas components of a mixture of gases will exert individual pressures in proportion to their mole fractions. The total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases.
Kinetic molecular theory
The average kinetic energy of a molecule of gas is directly proportional to the temperature of the gas in kelvins
Diffusion
The spreading out of particles from high to low concentrations
Effusion
The movement of gas from one compartment to another through a small opening under pressure
How do real gases deviate from ideal gases at modernly high pressure, low volumes or low temperatures?
They will occupy less volume than predicted by the ideal gas law because the particles have intermolecular attractions
How do real gases deviate from ideal gases at extremely high pressures, low volumes or low temperatures?
They will occupy more volume than predicted by the ideal gas law because the particles occupy physical space
Graham’s law of effusion
States that the relative rates of effusion of two gases at the same temperature and pressure are given by the inverse ratio of the square roots of the masses of the gas particles
Which factors affect a gas’s pressure?
Temperature and volume
If one of those two values is kept constant, the pressure will always be found
What does heating a gas at constant volume do?
Increase pressure
What does cooling a gas at constant volume do?
Decrease pressure
How can pressure be calculated when both volume and temperature are changing?
If both changes in volume and temperature have the same effect on pressure, then pressure can be predicted
e.g.
Cooling the gas and increasing its volume will both decrease pressure
What would increasing volume do to a gas if temperature is constant?
Decreases its pressure
What would decreasing volume do to a gas if temperature is constant?
Increases its pressure
Solvation
The breaking of intermolecular forces between solute particles and between solvent particles, with formation of intermolecular forces between solute and solvent particles
Solubility
The amount of solute contained in a solvent
How can the solubility of solids be increased?
Increasing the temperature
Which ions can form salts that are always soluble?
Group I metals, ammonium, nitrate and acetate salts
What is the solvent in aqueous solution?
Water
Saturation
The maximum solubility of a compound at a given temperature; one cannot dissolve any more of the solute just by adding more at this temperature
How can the solubility of gases be increased?
Decreasing temperature or increasing the partial pressure of the gas above the solvent (Henry’s law)
Colligative property
Physical properties of solutions that depend on the amount of solute present, but not the actual identity of the solute particles
How are molality and molarity related for water?
Molarity and molality are nearly equal at room temperature because 1 L solution if approximately equal to 1 kg solvent for dilute solutions (like the denominators of the molarity and molality equations, respectively).
How are molality and molarity related for solvents other than water?
Molarity and molality differ significantly because their densities are not 1 g/mL like water
Examples of colligative properties
Vapor pressure depression, boiling point elevation, freezing point depression and osmotic pressure
Percent composition by mass
= (mass of solute / mass of solution) x 100%
Used for aqueous solutions and solid-in-solid solutions
Mole fraction (Xa)
= moles of a / total moles of all species
Used for calculating vapor pressure depression and partial pressures of gases in a system
Molality (m)
= moles of solute / kilograms of solvent (mol/kg)
Used for boiling point elevation and freezing point depression
Dilution formula
Mi Vi = Mf Vf
Solubility product constant (Ksp)
= [A^n+]^m [B^m-]^n
The equilibrium constant for a dissociation reaction
Ion product (IP)
= [A^n+]^m [B^m-]^n
Determines the level of saturation and behavior of the solution
Raoult’s law (vapor pressure depression)
Pa = Xa Poa
The presence of other solutes decreases the evaporation rate of a solvent without affecting its condensation rate, thus decreasing its vapor pressure
Boiling point elevation (delta Tb)
= i Kb m
A shift in the phase equilibrium dependent on the molality of the solution
Freezing point depression (delta Tf)
= i Kf m
A shift in the phase equilibrium dependent on the molality of the solution
Osmotic pressure (pi)
= i M R T
Primarily depends on the molarity of the solution
Solution
Homogenous mixtures composed of two or more substances
Combine to form a single phase, generally the liquid phase
Solvent
Surrounds solute particles via electrostatic interactions in a process called salvation or dissolution
Hydration
Salvation in water
Are dissolutions endothermic or exothermic?
Endothermic
Is the dissolution of gas into liquid endothermic or exothermic?
Exothermic
How is solubility expressed?
As molar solubility
Molar solubility
The molarity of the solute at saturation
Complex ions (coordination compounds)
Composed of metallic ions bonded to various neutral compounds and anions (ligands)
Increase the solubility of otherwise insoluble ions (the opposite of the common ion effect)
How are complex ions formed?
The process involves electron pair donors and electron pair acceptors such as those seen in coordinate covalent bonding
IP < Ksp
The solution is unsaturated
If more solute is added, it will dissolve
IP = Ksp
The solution is saturated (at equilibrium)
There will be no change in concentrations
IP > Ksp
The solution is supersaturated
A precipitate will form
Formation (stability constant, Kf)
The equilibrium constant for complex formation
Its value is usually much greater than Ksp
Is Kf greater than or less than Ksp?
Greater than
Why does the formation of a complex ion increase the solubility of other salts containing the same ion?
Because it uses up the products of those dissolution reactions, shifting the equilibrium to the right (the opposite of the common ion effect)
Common ion effect
Decreases the solubility of a compound in a solution that already contains one of the ions in the compound. The pretense of that ion in solution shifts the dissolution reaction to the left, decreasing its dissociation.
As vapor pressure decreases, does the temperature (energy) required to boil the liquid increase or decrease?
Increase
van’t Hoff factor (i)
It is used in freezing point depression, boiling point elevation and osmotic pressure calculations for solutes that dissociate
What is the van’t Hoff factor (i) for a solute that does not dissociate into smaller components?
1
Raoult’s law
The ideal solution behavior is observed when solute-solute, solvent-solvent and solute-solvent interactions are all very similar
When is melting point depressed?
Upon solute addition
Solute particles interfere with lattice formation
Lattice formation
The highly organized state in which solid molecules align themselves
Is breaking the solute into its individual components an endothermic or exothermic process?
Endothermic
Energy is required to break molecules apart
Is making room for the solute in the solvent by overcoming intermolecular forces in the solvent an endothermic or exothermic process?
Endothermic
The intermolecular forces in the solvent must be overcome to allow incorporation of solute particles
Is allowing solute-solvent interactions to occur to form the solution an endothermic or exothermic process?
Exothermic
Polar water molecules will interact with the dissolved ions, creating a stable solution and releasing energy
Is a spontaneous reaction endothermic or exothermic?
Endothermic
Arrhenius acid
Dissociates to form excess H+ in solution
Arrhenius base
Dissociates to form excess OH- in solution
Bronsted-Lowry acid
H+ donor
Bronsted-Lowry base
H+ acceptor
Lewis acid
Electron pair acceptor
Lewis base
Electron pair donor
Amphoteric species
A species that can act as an acid or a base
If a compound has a Ka value»_space; water, what does it mean about its behavior in solution? How does this compare with a solution that has only a slightly higher Ka than water?
High Ka indicates a strong acid, which will dissociate completely in solution. Having a Ka slightly greater than water means the acid is a weak acid with minimal dissociation.
If a compound has a Kb value»_space; water, what does it mean about its behavior in solution? How does this compare with a solution that has only a slightly higher Kb than water?
High Kb indicates a strong base, which will dissociate completely in solution. Having a Kb slightly greater than water means the base is a weak base with minimal dissociation.
What is the mathematical relationship between Ka, Kb and Kw?
Ka x Kb = Kw
What species are considered the equivalents of acids and bases?
Acids use moles of H+ (H3O+) as an equivalent
Bases use moles of OH- as an equivalent
Buffering region in a titration curve
Occurs when [HA] ~= [A-]
The flattest portion of the titration curve (i.e. resistant to changes in pH)
Half-equivalence point in a titration curve
The center of the buffering region, where [HA] = [A-]
Equivalence point in a titration curve
The steepest point of the titration curve
Occurs when the equivalents of acid present equal the equivalents of base added (or vice-versa)
Endpoint in a titration curve
The pH at which an indicator turns its final color
In which part f the pH range will the equivalence point fall for titration with a strong acid with a weak base?
In the acidic range
In which part f the pH range will the equivalence point fall for titration with a strong base with a weak acid?
In the basic range
In which part f the pH range will the equivalence point fall for titration with a strong acid with a strong base?
pH = 7 (neutral)
In which part f the pH range will the equivalence point fall for titration with a weak acid with a weak base?
In the acidic range, basic range or neutral range, depending on the relative strengths of the acid and base
Buffer solution
Resists changes in pH and has optimal buffering capacity within 1 pH point from its pKa
Consist of a mixture of a weak acid and its conjugate salt or a weak base and its conjugate salt
Autoionization constant for water (Kw)
= [H3O+] [OH-] = 10^-14 (at 25 C, 298 K)
Definition of pH
= - log [H+] = log (1 / [H+])
Definition of pOH
= - log [OH-] = log (1 / [OH-])
Relationship of pH and pOH at 298 K
pH + pOH = 14
p scale value approximation
p value ~= m - 0.n
Acid dissociation constant (Ka)
= ([H3O+] [A-]) / [HA]
Base dissociation constant (Kb)
= ([B+] [OH-]) / [BOH]
Equivalence point
Na Va = Nb Vb
Henderson-Hasselbalch equation (acid buffer)
pH = pKa + log ([A-] / [HA])
Henderson-Hasselbalch equation (base buffer)
pOH = pKb + log ([B+] / [BOH])
Are all Arrhenius acids and bases also Bronsted-Lowry acids and bases?
Yes
Are all Bronsted-Lowry acids and bases also Lewis acids and bases?
Yes
Are all Lewis acids and bases also Bronsted-Lowry acids and bases?
No
Are all Bronsted-Lowry acids and bases also Arrhenius acids and bases?
No
Amphoteric species
Can behave as either acids or bases
Amphiprotic species
Amphoteric species that specifically can behave as a Bronsted-Lowry acid or base
Examples of amphoteric and amphiprotic species
Water and conjugate species of polyvalent acids and bases
What is the water dissociation constant (Kw, auto ionization constant of water) affected by?
Changes in temperature
Strong acids and bases
Completely dissociate in solution
Weak acids and bases
Do not completely dissociate in solution and have corresponding dissociation constants (Ka and Kb)
Bronsted-Lowry definition
Acids have conjugate bases that are formed when the acid is deprotonated. Bases have conjugate acids that are formed when the base is protonated. Strong acids and bases have very weak (inert) conjugates. Weak acids and bases have weak conjugates.
Neutralization reactions
Form salts and (sometimes) water
Equivalent
One mole of the species of interest
Normality
The concentration of acid or base equivalents in solution
Polyvalent acids and bases
Can donate or accept multiple electrons
What is the normality of a solution containing polyvalent species?
It is the molarity of the acid or base times the number of protons it can donate or accept
Titrations
Used to determine the concentration of a known reactant in a solution
Titrant
Has known concentration and is added slowly to the titrand to reach the equivalence point
Titrand
Has an unknown concentration but a known volume
Indicators
Weak acids or bases that display different colors in their protonated and deprotonated forms
How should the indicator for a titration be chosen?
The indicator should have a pKa close to the pH of the expected equivalence point
Titration curve or polyvalent species
Has multiple buffering regions and equivalence points
Buffering capacity
Refers to the ability of a buffer to resist changes in pH
When is maximal buffering capacity seen?
Within 1 pH point of the pKa of the acid in the buffer solution
Henderson-Hasselbalch equation
Quantifies the relationship between pH and pKa for weak acids and between pPH and pKb for weak bases
When a solution is optimally buffered, pH = pKa and pOH = pKb
Acids ending in -ic
Derivatives of acids ending in -ate
Acids ending in -ous
Derivatives of acids ending in -ite
Strong bases
Soluble hydroxides of Group IA and IIA metals
Ka = 1
Strong acid
Oxidation
Loss of electrons
Reduction
Gain of electrons
Oxidizing agent
Facilitates the oxidation of another compound and is reduced itself in the process
Reducing agent
Facilitates the reduction of another compound and is itself oxidized in the process
Common oxidizing agents
Contain oxygen or a similarly electronegative element
Common reducing agent
Contain metal ions or hydrides
Half-reaction method (ion-electron method)
- Separate the two half-reactions
- Balance the atoms of each half-reaction
- Balance the charges of each half-reaction by adding electrons
- Multiply the half-reactions as necessary to obtain the same number of electrons in both half-reactions
- Add the half-reactions, cancelling out terms on both rides of the reaction arrow
- Confirm the mass and charge are balanced
Complete ionic equation
Accounts for all of the ions present in a reaction
How to write a complete ionic equation?
Split all aqueous compounds into their relevant ions. Keep solid salts intact
Net ionic equation
Removes spectator ions to focus only on the species that actually participate in the reaction
How to obtain the net ionic reaction?
Subtract the ions appearing on both sides of the reaction
Spectator ions
Ions appearing on both sides of the reaction
For reactions that contain no aqueous salts, what does the net ionic equation look like?
It is generally the same as the overall balanced reaction
For double displacement (metathesis) reactions that do not form a solid salt, what does the net ionic equation look like?
There is no net ionic equation because all ions remain in solution and do not change oxidation numbers
Disproportionation (dismutation) reaction
A type of reduce reaction in which one element is both oxidized and reduced forming at least two molecules containing the element with different oxidation states
Oxidation-reduction titrations
Follow the transfer of charge
Use indicators to indicate when certain voltages of solutions are achieved
Potentiometric titration
A form of redox titration in which a voltmeter or external cell measures the electromotive force (emf) of a solution
No indicator is used
The equivalence point is determined by a sharp change in voltage
What is the site of oxidation in a galvanic (voltaic) cell?
Anode
In a galvanic (voltaic) cell, what to electrons flow towards?
Cathode
In a galvanic (voltaic) cell, what does current flow towards?
Anode
In a galvanic (voltaic) cell, what has a (-) designation?
Anode
In a galvanic (voltaic) cell, what attracts cations?
Cathode
What is the site of oxidation in an electrolytic cell?
Anode
In an electrolytic cell, what to electrons flow towards?
Cathode
In an electrolytic cell, what does current flow towards?
Anode
In an electrolytic cell, what has a (-) designation?
Cathode
In an electrolytic cell, what attracts cations?
Cathode
Cell diagram for the discharging state of a lead-acid battery
Pb (s) | H2SO4 (4 M) || H2SO4 (4 M) | PbO2 (s)
Which type of cell has a positive delta G?
Electrolytic cells (because they are non spontaneous)
Which type of cell has a positive Ecell?
Galvanic (voltaic) cells (because they are spontaneous and have a negative delta G and therefore a positive Ecell)
Is Ni-Cd (discharging) galvanic or electrolytic?
Galvanic
Is Ni-Cd (charging) galvanic or electrolytic?
Electrolytic
Is molten NaCl (discharging) galvanic or electrolytic?
Electrolytic
Is Daniell cell (discharging) galvanic or electrolytic?
Galvanic
Is lead-acid (charging) galvanic or electrolytic?
Electrolytic
Is lead-acid (discharging) galvanic or electrolytic?
Galvanic
What is the anode material in Ni-Cd (discharging)?
Cd
What is the anode material in Ni-Cd (charging)?
Cd(OH)2
What is the anode material in molten NaCl (discharging)?
Anything
What is the anode material in Daniell cell (discharging)?
Zn
What is the anode material in lead-acid (charging)?
PbSO4
What is the anode material in lead-acid (discharging)?
Pb
What is the anode charge in Ni-Cd (discharging)?
Negative
What is the anode charge in Ni-Cd (charging)?
Positive
What is the anode charge in molten NaCl (discharging)?
Positive
What is the anode charge in Daniell cell (discharging)?
Negative
What is the anode charge in lead-acid (charging)?
Positive
What is the anode charge in lead-acid (discharging)?
Negative
What is the cathode material in Ni-Cd (discharging)?
NiO(OH)
What is the cathode material in Ni-Cd (charging)?
Ni(OH)2
What is the cathode material in molten NaCl (discharging)?
Anything
What is the cathode material in Daniell cell (discharging)?
Cu
What is the cathode material in lead-acid (charging)?
PbSO4
What is the cathode material in lead-acid (discharging)?
PbO2
What is the cathode charge in Ni-Cd (discharging)?
Positive
What is the cathode charge in Ni-Cd (charging)?
Negative
What is the cathode charge in molten NaCl (discharging)?
Negative
What is the cathode charge in Daniell cell (discharging)?
Positive
What is the cathode charge in lead-acid (charging)?
Negative
What is the cathode charge in lead-acid (discharging)?
Positive
How are standard reduction potentials measured?
Setting up a cell relative to a standard hydrogen electrode, with is given a reduction potential of 0 V by convention
Positive emf
The cell is spontaneous (galvanic)
Negative emf
The cell is non spontaneous (electrolytic)
Is:
2 Fe^3+ (aq) + 2 Cl- (aq) –> 2 Fe^2+ (aq) + Cl2 (g) || Ecell = -0.59 V
galvanic or electrolytic?
Electrolytic, because emf is negative
Is:
2 Fe^3+ (aq) + 2 I- (aq) –> 2 Fe^2+ (aq) + I2 (aq) || Ecell = +0.25 V
galvanic or electrolytic?
Galvanic, because emf is positive
If Keq = 1.2e-2, is delta G positive or negative?
Positive
If Keq = 2e2, is delta G positive or negative?
Negative
If Keq = 1 is delta G positive or negative?
0
If Keq = 1.2e-2, is the reaction spontaneous or non spontaneous?
Nonspontaneous
If Keq = 2e2, is the reaction spontaneous or non spontaneous?
Spontaneous
If Keq = 1, is the reaction spontaneous or non spontaneous?
The cell is in equilibrium
If Keq = 1.2e-2, is Ecell positive or negative?
Negative
If Keq = 2e2, is Ecell positive or negative?
Positive
If Keq = 1, is Ecell positive or negative?
0
What is the direction of the reaction if Q = 10^-3 and Keq = 10^-2?
Forward
What is the direction of the reaction if Q = 10^2 and Keq = 1.1?
Backward
What is the direction of the reaction if Q = 1 and Keq = 1?
The reaction is in equilibrium
If Q = 10^-3 and Keq = 10^-2, is Ecell positive or negative?
Positive
If Q = 10^2 and Keq = 1.1, is Ecell positive or negative?
Negative
If Q = 1 and Keq = 1, is Ecell positive or negative?
0
How is the equation:
delta G = - R T ln Keq
affected if Keq < 1?
ln Keq < 0 and delta G > 0
How is the equation:
delta G = - R T ln Keq
affected if Keq > 1?
ln Keq > 0 and delta G < 0
How is the equation:
delta G = - R T ln Keq
affected if Keq = 1?
ln Keq = 0 and delta G = 0
Moles of electrons transferred during reduction
M^n+ + n e- –> M (s)
Electrodeposition equation
mol M = (I t) / (n F)
Standard electromotive force of a cell (Ecell)
= E red, cathode - E red, anode
The difference in standard reduction potential between the two half-cells
Standard change in free energy from standard emf (delta G)
= - n F Ecell
Nernst equation (full)
Ecell = Ecell - ([{R T} / {n F}] ln Q)
Describes the relationship between the concentration of species in a solution under nonstandard conditions and the electromotive force
Nernst equation (simplified)
Ecell = Ecell - (0.0592 / n) log Q
Reaction quotient (Q)
= ([C]^c [D]^d) / ([A]^a [B]^b)
Standard change in free energy from equilibrium constant (delta G)
= - R T ln Keq
Free energy change (nonstandard conditions) (delta G)
= delta G standard + R T ln Q
Electrochemical cell
Any cell in which oxidation-reduction reactions take place
Characteristics of electrochemical cells
Electrodes, anodes, cathodes, electrons flow from the anode to the cathode, and current flowed from the cathode to the anode
Electrodes
Strips of metal or other conductive materials placed in an electrolyte solution
Anode
The site of oxidation
Attracts anions
Cathode
The site of reduction
Attracts cations
Cell diagrams
Shorthand notation that represent the reactions taking place in an electrochemical cell
Written from anode to cathode with electrolytes (the solution) in between
A cortical line represents a phase boundary, and a double vertical line represents a salt bridge or other physical boundary
Galvanic (voltaic) cell
Spontaneous (delta G < 0)
Positive electromotive force
Electrolytic cell
Nonspontaneous (delta G > 0)
Negative electromotive force
Concentration cell
Specialized form of galvanic cell in which both electrodes are made of the same material
Rather than a potential difference causing the movement of charge, it is the concentration gradient between the two solutions
Rechargeable batteries
Electrochemical cells that can experience charging (electrolytic) and discharging (galvanic) states
Ranked by energy density
Energy density of a rechargeable battery
The amount of energy a cell can produce relative to the mass of battery material
Lead-acid batteries (discharging)
Consist of a Pb anode and a PbO2 cathode in a concentrated sulfuric acid solution
Lead-acid batteries (charging)
PbSO4-plated electrodes are dissociated to restore the original Pb and PbO2 electrodes and concentrate the electrolyte
Do lead-acid batteries have high or low energy density?
Low
Are lead-acid batteries rechargeable?
Yes
Nickle-cadmium batteries (Ni-Cd) (discharging)
Consist of a Cd anode and a NiO(OH) cathode in a concentrated KOH solution
Nickle-cadmium batteries (Ni-Cd) (charging)
Ni(OH)2 and Cd(OH)2-plated electrodes are dissociated to restore the original Cd and NiO(OH) electrodes and concentrate the electrolyte
Do Ni-Cd batteries have high or low energy density?
Low, but higher than that of lead-acid batteries
Are Ni-Cd batteries rechargeable?
Yes
Nickel-metal hydride (NiMH) batteries
Replace Ni-Cd batteries because they have higher energy density, are more cost effective and are less toxic
Do NiMH batteries have high or low energy density?
High, higher than those of lead-acid batteries and Ni-Cd batteries
Are NiMH batteries rechargeable?
Yes
Surge current
An above-average current transiently released at the beginning of the discharge phase, it eases rapidly until a stable current is achieved
Reduction potential
Quantifies the tendency for a species to gain electrons and be reduced
What does a higher reduction potential mean?
The more the species wants to be reduced
Standard reduction potential (Ered)
Calculated by comparison to the standard hydrogen electrode (SHE) under the standard conditions of 298 K, 1 atm pressure and 1 M concentrations
Standard hydrogen electrode (SHE)
Has a standard reduction potential of 0 V
In a galvanic cell, what is the sign of the difference of the reduction potentials of the two half reactions?
Positive
In an electrolytic cell, what is the sign of the difference of the reduction potentials of the two half reactions?
Negative
How are the signs of electromotive force and change in free energy relate to one another?
They are always opposites of each other
In a galvanic cell, can the reduction potential of the cathode be less than that of the anode?
No
Keq in an electrolytic cell
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