Chemistry Flashcards
_______________
- The number of protons in the atoms nucleus
Atomic number
_______________
- The number of protons and neutrons in the atoms nucleus
Mass number
_______________
- Same number of protons and electrons, but different number of neutrons
Isotope
_______________
- An atom that has lost electrons
Cation
_______________
- an atom that has gained electrons
Anion
True or false : Bohrs model explains emission of specific spectral lines from hydrogen atom
True
_______________
- are accurate models of where electrons reside outside of nucleus
Orbitals
The s orbital has ______ orientation(s)
The p orbital has ______ orientation(s)
The d orbital has ______ orientation(s)
1
3
5
_________ principle
- atomic orbitals are filled from the lowest energy orbital to the highest energy orbital until all electrons are used
Aufbau principle
____________
- Electrons in the highest energy orbitals
Valence electrons
____________principle
- only 2 electrons may be placed in one or a little at a time and they must have opposite spins
Pauli exclusion principle
____________
- orbitals of equal energy must first be filled singly with electrons of the same spin and then paired with electrons of opposite spin
Hund’s rule
____________
- when an atom absorbs energy, its electrons move to higher energy levels
Energy transition
____________
- The energy level of an electron prior to energy absorption
Ground state
____________
- The energy level of an electron after energy absorption
Excited state
An electron stays at the excited state for a brief period, and then relaxes back to the ground state causing energy to be admitted as _______________
Electromagnetic radiation
____________ can be produced from both atomic energy, absorption and emission experiments (characteristic of the element, and can be used to determine the identity of an unknown substance)
Spectra
____________
- experimental procedure to determine precise mass and relative abundance of isotopes in a substance
Mass spectrometry
____________ operation
- a sample is introduced into the instrument and vaporized
- Vaporize the particles are ionized (creating positively charged radical cations)
- Ions undergo further fragmentation into lower mass ions (occurs through a magnetic field, which separates them by mass)
- Ions leave magnetic field and are detected in the order of highest to lowest mass
Mass spectrometer
____________
- Fragmentation patterns
- Are unique to the substance
- Provide molecular weight directly
- Molecular formula can be determined
Spectra
____________
- A property predictable from the elements position in the periodic table
Periodic property
Atom size (radii) __________ down a group & __________ from left to right across period
Increase
Decrease
Atomic radii __________ with gain of electrons & __________ with loss of electrons
Increase
Decrease
____________
- Energy required to remove an electron from an atom or ion and its gaseous state
- values always positive
Ionization energy
____________
- removal of highest energy electron
First ionization energy
Ionization energy generally __________ down a group & __________ from left to right
Decrease
Increase
_______________
- Energy change associated with gain of an electron by an atom in gaseous state
- usually exothermic
Electron affinity
Most groups do not exhibit a trend in electron affinity but group 1 elements become more positive down a group
Electron affinity generally becomes more __________ from left to right in a period
Negative (exothermic)
_______________
- The ability of an atom to attract electrons in a covalent bond
- Values range from 0.7 - 4.0 using the pauling scale (values are unitless)
Electronegativity
Electronegativity _________ down a group & __________ from left to right in a period
Decreases
Increases
_______________
- electrostatic attraction between 2 oppositely charged ions (usually a metallic cation & a nonmetallic anion)
- Due to lowering of potential energy between oppositely charged ions
Ionic bond
The potential energy of attraction between two oppositely charged ions is estimated by using _______________
Coulomb’s law
_______________
- are energy associated with formation of a crystal of alternating ions from gaseous ions (values are always negative)
Lattice energy
As ions become larger, the △H-lattice becomes less __________
Less negative (less exothermic)
As charges of ions increase, △H-lattice becomes more __________
Negative (more exothermic)
_______________
- when 2 atoms share valence electrons between their nuclei
- there potential energies are lowered through electrostatic attraction
- Typically nonmetals
Covalent bonds
_______________
- to the drawing, representing covalent bonds between atoms as shared or transferred electrons
- Based on the molecular formula
Lewis structures
All elements except for _____ & _____ prefer 8 electrons around their nuclei
H
He
When there are several Lewis structures, then ____________ occurs and they can be combined to form a hybrid
Resonance
_______________
- used to determine the best Lewis structure
- FC = Atoms Group # - (bonds + unpaired electrons)
- “normal valence - (lines +dots)”
- a compound’s total charge must equal the sum of all its atoms formal charges
Formal charge
When 2 atoms in a covalent bond have the same electronegativity then the atoms share valence electrons equally so such bonds do not have a dipole moment and are termed _______________
Nonpolar
When atoms in a bond have different electronegativities in a dipole moment, occurs in the covalent bond is termed _______________
Polar
When the difference in electronegativites between atoms in a bond is very large then an __________ interaction occurs because electrons are transferred to the more electronegative atom
Ionic
_______________ theory
- one of several techniques that can be used to predict the shapes of molecular compounds
- based on the idea that electrons with similar charges repel each other
- when only bonding electron pairs are considered than 5 shapes are predicted
- other shapes are predicted when a pair of bonding electrons is replaced with a pair of non-bonding electrons
Valence Shell Electron Pair Repulsion theory
VSEPR
When 1 bonding group of the principle tetrahedral shape is replaced with a lone pair. The shape is now called _______________ and has bond angles of _________
Trigonal pyramidal
~107 degrees
When 2 bonding groups of the principal tetrahedral shape is replaced with two lone pairs in the shape is called _______________ and had bond angles of _________
Bent
~105 degrees
True or false : Polarized bond exist in a molecule than the overall molecule may or may not be polar because the shape in the orientation of dipole moment can be used to predict Molecular polarity
True
_______________ theory
- approach to predicting length and strength of covalent bonds qualitatively and molecular compounds
- also predicts 3D shapes of molecules
3 basic principles
- Overlap of atomic orbitals containing unpaired valence electrons
- Localization of valence electrons in the orbital overlap region between atoms
- Formation of hybrid orbitals from atomic orbitals to optimize orbital overlap between bonding atoms
Valence bond theory
___________ bonds
- form by the end-to-end overlap of atomic and hybrid orbitals containing unpaired electrons
- bonded atoms share electrons between them
Sigma bonds
___________ bonds
- form by side to side, overlap of atomic orbitals, usually p orbitals
-are longer & only about 3/4 as strong as sigma bonds
- can form only in conjunction with sigma bonds (cannot exist without a sigma bond)
Pi bonds
_______________
- compounds differ in some ways, but have same molecular formula
Chemical isomers
_______________
- same molecular formula, but differ in the way the atoms in the molecule are bonded to each other
Structural isomers
“Constitutional isomers”
_______________
- same molecular formula and connectivity a differ in the way the atoms are arranged
- cannot be interconverted by sigma bond rotation (“single bond”)
Stereoisomers
_______________
- usually a carbon atom that is sp3 hybridized & has 4 different atoms or groups of atoms attached to it
Chirality Center
Stereoisomers have 2 categories
_______________
_______________
Enantiomers
Diastereomers
_______________
- nonsuperimposable mirror images of each other
- always come in pairs (the left and right handed isomers of a compound)
- always contain at least 1 chirality center
- a pure enantiomer is optically active & rotates plane-polarized light
Enantiomers
_______________
- not mirror image stereoisomers of each other
- includes all forms of stereoisomers except enantiomers
Diastereomers
Process of R and S assignment of absolute stereochemistry to chirality centers
- each of 4 groups bonded to chiral carbon in chirality center is assigned a priority
- priorities are assigned using the _____________________ protocol
- lowest priority group is position behind chiral carbon, leaving the remaining high priority groups in a trigonal planar configuration. If priorities of groups around the chiral carbon are 1 to 2 to 3 in a clockwise direction then the center is designated R & and if the priorities are counterclockwise in the center is designated S
Cahn-Ingold-Prelog (CIP) protocol
Stereoisomers of certain organic compounds (specifically alkenes) occur as a type of diastereomer & can be distinguished as ________ or ________
Cis-
Trans-
__________ configuration
- 2 atoms of the same type are on opposite sides of double bond
Trans- configuration
___________ configuration
- 2 atoms of the same type are on the same side as of double bond
Cis- configuration
_______& ________ assignment
- common protocol to distinguish alkene stereoisomers
E (entgegen = opposite)
Z (zusammen = together)
E and Z designations are most commonly used when there are no like groups attached to the double bond, but they can be used to indicate the stereochemistry of any alkene. The procedure for assigning E and Z to a specific stereoisomer (use C-I-P prioritization rules)
- When highest priority groups are on opposite sides of the double bond, the isomer is designated as _____
- when highest priority groups are on the same side of the double bond, it is designated as _____
E
Z
_______________
- heat required to raise the temperature of a substance by 1°C
Heat capacity
_______________
- heat required to raise the temperature of 1 g of a substance by 1°C
Specific heat capacity
_______________
- temporary structural isomerism to study energy changes because sigma bonds have freedom of rotation (parts of molecule can move many ways)
Conformational analysis
_______________
- 2 different conformational if structures of ethane
Sawhorse structures
____________ conformations of ethane
- all H aligned & high energy due to torsional strain
____________ conformations of ethane
- no H aligned & low energy
Eclipsed conformations
Staggered conformations
A ___________________ , useful in alkane stereochemistry, visualizes the conformation of a chemical bond from front to back, with a line representing the front atom and a circle representing the back carbon. The carbon atom at the front is called proximal, while the atom at the back is called distal.
Newman projection
In cyclohexane conformations the lowest energy conformation is called the _________ (with almost no ring strain)
Chair
Chair conformation has 2 different types of substitute bonding positions where H & other substitutes are attached to ring. These positions are ________ (bonds, extend directly above & below the ring) and ____________ (bonds are oriented at ~ 45° angles around the equator of the ring)
Axial
Equatorial
Any chair conformation with a substitute larger than an H-atom has lower energy (more stable) with substitute in equatorial position, so lowers ____________
Steric strain
True or false:
Gases differ from the condensed phases of liquids & solids in a number of ways
- Gas volume changes greatly with pressure
- Gas volume changes greatly with temperature
- Gases have low viscosity
- Gases are always miscible with each other
True
True or false:
Ideal gases do not exist. A true ideal gas would be made up of molecules that have no interaction with each other (no attractive forces) and zero volume. Helium is the closest to an ideal gas.
True
Measurable parameters of ideal gases can be estimated from
_____________ law
_____________ law
_____________ law
Charles law
Boyles law
Avogadro’s law
_______________
- volume of gas directly proportional to temperature
- P and n held constant
Charles law
_______________
- volume of gas inversely proportional to pressure
- T and n held constant
Boyles law
_______________
- volume of gas is directly proportional to amount of gas
- P and T held constant
Avogadro’s law
____________ law
- PV = nRT
- Basic gas relationships can be combined to give a single law (Charles, Boyles, & Avogadro’s)
Ideal gas law
_______________
- models, an ideal gas as a collection of point particles constantly in motion & undergoing completely elastic collisions
- Explains Avogadro’s law
- For any ideal gas at standard temperature and pressure (STP) [1 mole gas = 22.4 L]
Kinetic-molecular theory
_______________
- any gas mixture, each gas ask independently so that any overall property of the mixture is the sum of the properties of the individual components
- Some of the individual gas pressures (partial pressures) must equal total pressure (P-total = P-a + P-b + P-c …..)
- if total pressure of mixture is known, partial pressure of any component can be determined
Dalton’s law of partial pressures
_____ gas behavior
- Real gases deviate from ideal gas properties to different degrees under various conditions
- At high pressures (>20 atm) the molar volume is greater than that of ideal gas
- At low temperatures (<200K), the stronger attractions between gas particles lower number of collisions on surface of a container, lowering pressure compared to ideal gas
Real
The _____________ equation is used to correct for high pressure & low temperature effects
- P + a(n/V)^2 • (V - nb) = nRT
- P + a(n/V)^2 : corrects for intermolecular forces
- (V - nb) : correct for molar volume (a & b are constants for specific gases)
Van der Waal’s equation
__________
- A condensed phase of matter
- atoms & molecules packed as closely as in a solid, but can move relative to each other
- A fixed volume but not a fixed shape (shape of its container)
- Properties : vapor pressure, boiling point, viscosity, & surface tension
Liquids
__________
- attractive & repulsive forces between atoms and molecules in a liquid
- Hold condensed phases of matter together
- Ion-dipole, H bonds, dipole-dipole, & London dispersion
Intermolecular forces
__________
- between ion and oppositely charged end of polar molecule
Ion dipole
__________
- very strong dipole-dipole attractive force between a hydrogen atom bonded to a highly electronegative atom on a neighboring molecule
- “FON”
Hydrogen bonding
__________
- exhibited by polar molecules
- due to uneven distribution of electrons
Dipole-dipole
__________
- exhibited by all atoms and molecules
- Due to instantaneous polarization of their electron clouds
London dispersion
__________
- SI unit used to convert between particles of a substance and mass
- 1 mall of a substance = number of atoms in 12 grams of carbon-12
- Numerical value for number of particles in a mole of anything is called Avogadro’s number (6.0221421 x 10^23)
Mole
__________
- mass in grams of one mole of an element
- Equals the atomic mass of the element in atomic mass units (amu)
Molar mass
__________
- lowest whole number ratio of elements in a compound
Empirical formula
__________
- actual number of atoms of each element in the compound
Molecular formula
__________
- shows all the atoms present in the compound and how they are bonded to each other
- Can be shown in both 2-D and 3-D space
Structural formula
3 categories of chemical reactions
____________
____________
____________
Precipitation
Acid base
Oxidation reduction
__________
- 2 soluble ionic compounds react in aqueous phase to produce 1 or more insoluble ionic compounds called precipitates (the product)
- reaction generally follows only 1 pattern called double replacement (AB + CD —> AD + CB)
- when metal ions switch counter ions either AD or CB may be a precipitate (it will be denoted as solid)
Precipitation
Water _________ rules for ionic compounds predict formation of precipitate
Water solubility rules
______________ (neutralization)
- combination of an acid and a base in aqueous phase to produce water and an ionic compound (salt), and sometimes a gas
- Acid = proton donor & Base = proton, acceptor
Acid base reactions
________________ reactions
- transfer of electrons between reactant atoms
- Atoms of 1 element lose electrons & atoms of 1 element gain electrons
Oxidation reduction reactions (redox)
Most common reaction patterns for redox reactions :
____________ : A + B —> C
____________ : C —> A + B
____________ : A + BC —> AC + B
____________ : CxHy + (x + 1/4y)O2 —> xCO2 + 1/2yH2O
Addition
Decomposition
Single displacement
Combustion
To determine if electron transfer has occurred, atoms in reactants & products are assigned _______________
Oxidation numbers
______________
- The relationship between amount of reactants & products in a balanced chemical equation
Stoichiometry
A reaction unit factor (mole : mole ratio) is based on a _______________
Balanced equation
______________
- reactant in balanced stoichiometric equation that is used up first
- once reactant used up then reaction stops & no more product is formed
Limiting reactant (reagent)
______________
- greatest possible amount of a specific product that can be obtained from a specific chemical reaction
- always a calculation based on a stoichiometric relationship obtained from a balanced equation
Theoretical yield
______________
- yield of a specific product obtained from a specific chemical reaction
- Always based on an actual laboratory experiment, process, or personal experience
Actual yield
______________
- a measure of how efficient a reaction is in producing a specific product
- Always <100%
- (Actual yield / Theoretical yield) x 100%
Percent yield
______________
- Study of the relationship between chemical processes & energy
- most common units are the joule (J) and calorie (cal)
Thermochemistry
______________
- General study of energy and its inter-conversions
- Energy can be neither created nor destroyed & is always conserved
Thermodynamics
______________
- The total energy of the universe is constant.
First law of thermodynamics
______________
- sum of Kinetic Energies & Potential Energies of all particles of a system
Internal energy (E)
True or false :
Estimating a change in E requires only initial and final values
True
E = E-final - E-initial
Any thermodynamic process, energy loss & energy gain are defined in terms of the __________ and the __________
System
Surroundings
Overall internal energy change of a system involves 2 types of energy changes :
____________
____________
Heat (q)
Work (w)
______________
- A special type of thermal energy, or heat, that is a state function
- The change in H of a system at constant pressure is the sum of its △E & the product of its pressure (P) & change in volume (△V)
- △H = △E + P△V
Enthalpy
If the heat/work equation and the enthalpy equation are combined then enthalpy is shown as _______________
Heat at constant pressure (qp)
__________ process
- △H is negative (-)
- System is losing heat to surroundings
Exothermic process
____________ process
- △H is positive (+)
- System is absorbing heat from surroundings
Endothermic process
Breaking chemical bonds is an ___________ process
Endothermic (energy absorbed)
Forming chemical bonds is an _____________ process
Exothermic (energy released)
____________
- an experimental technique that uses a Calorimeter to measure heat change for a process (often a chemical reaction)
Calorimetry
____________
- A device used to measure heat, released or absorbed by a physical or chemical process that takes place inside it
- Process is the system and the calorimeter is the surroundings
Calorimeter
______________ calorimetry
- measurement of heat changes of a system using a bomb calorimeter at constant volume
- Used to estimate △E of a system (qv = △E)
Constant-volume Calorimetry
_______________ calorimetry
- measurement of heat changes of a system using an open calorimeter at constant pressure
- Used to estimate △H of the system (qp = △H)
Constant pressure Calorimetry
__________
- A measure of the randomness or disorder of a system
- S = k ln W
Entropy
_________________
- for any spontaneous process the entropy of the universe increases
The second law of thermodynamics
____________
- A process that occurs by itself under natural conditions
Spontaneous process
If △S-univ > 0 , a process will be ______________
Spontaneous
An ____________ process increases △S-surr
Exothermic
An ____________ process decreases △S-surr
Endothermic
________________
- The entropy of a perfect crystal at absolute zero temperature is zero
Third law of thermodynamics
_______________
- entropy values at standard states
- Used to calculate standard entropy changes for chemical reactions
Standard molar entropies
_______________
- State function that combines a processes enthalpy and entropy changes
- Indicates a reactions spontaneity
Gibbs free energy (G)
△G < 0 means process is ______________
Spontaneous ( exergonic)
△G > 0 means process is ______________
Nonspontaneous (endergonic)
△G = 0 means process is ____________
At equilibrium
____________________
- at a given temperature, chemical reaction reaches a state at which a particular ratio of reactant & product concentrations has a constant value
The law of chemical equilibrium
____________________
- concentration of the product(s) raised to the balanced equation coefficients divided by the reactant(s) raised to their balanced equation coefficients, when the overall process has reached equilibrium
Equilibrium constant (Kc)
____________
- same ratio as K except overall reaction need not be at equilibrium
Reaction quotient (Q)
If Q < K , the reaction will progress toward ____________ until equilibrium is established
Products
If Q > K , the reaction will progress toward ___________ until equilibrium is established
Reactants
If Q = K , the reaction is at ____________
Equilibrium
Reaction quotient (Q) it’s not a constant & can’t have any value depending on product: reactant ratio
- if Q = 0 then reaction has only __________
- If Q = ∞ then reaction has only __________
- If Q = 1 then reaction has equal product and reactant concentrations
Reactants (no products)
Products (no reactants)
_______________
- if a system at equilibrium is disturbed, position of equilibrium shifts to minimize disturbance
Le Chatelier’s principle
Effect of concentration changes on equilibrium (at constant temp)
- Shift away from side where chemicals are ______ & shift toward side where chemicals are _______
- Adding a reactant __________ amounts of other reactants & ________ amount of products, until a new equilibrium is reached (value of K does not change)
- Removing a product ________ amounts of other products & __________ amount of reactants, until I knew equilibrium is reached (value of K does not change)
- Added & Removed
- Decreases & Increases
- Increases & Decreases
Effect of volume changes on equilibrium :
- when pressure is increased, equilibrium shifts towards the side with ________ molecules to decrease the pressure until new equilibrium
- when pressure is decreased, equilibrium shifts toward the side with ________ molecules to increase the pressure until new equilibrium
- Value of K does not change of temperature is constant
Fewer
More
True or false
Effect of temperature changes on equilibrium (temp change does affect K) :
- Increasing temperature of endothermic reaction is like adding heat to the reactant side of the chemical equation
- Adding heat to an endothermic reaction, decreases concentrations of reactants and increases concentrations of products
- Increasing temperature of an exothermic reaction is like adding heat to the product side of the chemical reaction
- Adding heat to an exothermic reaction, decreases concentrations of products and increases concentrations of reactants
True
____________ favored reaction
- process moves spontaneously (△ G < 0) toward products until equilibrium is reached (K > 0)
- More products than reactants
Product favored reaction
__________ favored reaction
- process moves spontaneously (△G < 0) toward products until equilibrium is reached (K < 1)
- More reactants than products
Reactant favored reaction
_______________
- a homogenous mixture of 2 or more substances
- often just 2 components : solvent and solute
Solution
_______________ solution
- solvent still has a capacity for more solute molecules or ions
- If more solute is added, solute will dissolve & its concentration will be higher
Unsaturated solution
_______________ solution
- solvent’s capacity for solute molecules or ions has been reached
- If more solute is added, solute will not dissolve and concentration in solvent remains the same
Saturated solution
_______________ solution
- solvents capacity exceeded
- Due to unusual conditions, excess solute remains dissolved (related to entropy)
- A slight disturbance of system usually leads to precipitation of excess solute
Supersaturated solution
_______________
- an equilibrium constant for dissolving a slightly soluble ionic compound in water
- Values range from ~1x10^-4 to 1x10^-70
- calculated from an ion–product expression for a slightly soluble salt
Solubility product constant (Ksp)
_______________
- if 2 solutes, 1 highly soluble & 1 slightly soluble share a common ion, the common ion decreases solubility of slightly soluble compound
Effect of a common ion on solubility (common ion effect)
_______________
- solubility of ionic compounds that contain an anion from a weak acid increases when pH of the solution is low (acidic)
Effect of pH on solubility
_______________
- A species consisting of a central metal ion bonded to molecules and/or anions called ligands
Complex ions
For an ionic compound with a transition metal cation, that forms complex ions, solubility increases in presence of _____________ that form a complex with the cation
Lewis bases (e.g. NH3)
Brønsted-Lowry acid definition of an acid is a proton ________ (H+)
Donor
Acid strengths are relative to their ability to donate ___________
Protons (H+)
__________
- donate all their protons to water to form large amounts of hydronium ions (H3O+)
- At equilibrium, almost none of the original acid is unreacted
Strong acids
_______________
- donate only some of their protons to water to form relatively small amounts of hydronium ions (H3O+)
- At equilibrium, most of the original acid is unreacted
Weak acids
_______________
- an equilibrium constant that defines extent of a weak acids dissociation
Acid ionization constant (Ka)
_______________
- an equilibrium constant that defines extent that water acts as a weak acid by donating a proton to another water molecule to form minute, amounts of hydronium ions and hydroxide ions
Water autoionization constant (Kw)
Kw relationship :
[H3O+] > [OH-] —> ______solution
[H3O+] < [OH-] —> ______solution
[H3O+] = [OH-] —> ______solution
Acidic
Basic
Neutral
_______________
- A negative, base 10 log scale of weak acid ionization constants
pH scale
Brønsted-Lowry definition of a base is a proton _____________ (H+)
Acceptor
_______________bases
- always metallic salts of hydroxide anion
- if soluble in water, dissociate almost completely into aqueous solution
Strong bases
_______________ bases
- do not directly contain hydroxide anions but generate minute amounts of hydroxide anion
weak bases
_______________
- equilibrium constant that defines extent of a weak bases formation of OH-
Base ionization constant (Kb)
_______________
- a negative base 10 log scale of weak bases ionization constants
pOH scale
Anions of weak acids (the acids conjugate base) act as ____________
Weak bases
Anions of strong acids (the acids conjugate base) are __________
Neutral
Cations that are counterions of strong bases (OH-) are ____________
pH neutral
Cations of weak bases (the bases conjugate acid) act as ____________
Weak acids
Small highly charged metal cations form weakly ___________ solutions
Acidic
Acid base properties of salt solutions :
- __________ solutions from salts with Anions of Strong Acids & Cations of Strong Bases
- __________ solutions from salts with Anions of Strong Acids & Cations of Weak Bases
- __________ solutions from salts with Anions of Weak Acids & Cations of Strong Bases
Neutral
Acidic
Basic
_______________
- a solution of water-soluble compounds that resists pH changes
Buffer
_______________
- solutions with 2 species that share a common ion resist becoming more acidic (buffering effect)
Common ion effect
_______________
- procedure for determining concentration of a solution using another solution of known concentration
Titration
_______________ titration
- to estimate an unknown acids concentration, a base solution of known concentration is added until the acid and base have just completely reacted. The reaction is complete when an added indicator changes color (end point)
Acid base titration
_______________
- Point in a titration, at which number of moles of a substance of known concentration is equal to number of moles of unknown substance
Equivalence point
The equivalence point is best estimated from a ____________
Titration curve
- the inflection point of curve represents the EP
_______________
- Study of rate at which chemical transformations occur
- Change in the concentration of reactants or products relative to time usually used to estimate reaction rates
Chemical kinetics
_______________
- rate of change of reactant or product concentrations during a defined time interval
Average reaction rates
Average rates ____________ as the reaction progresses from reactants to products due to the ever increasing rate of reverse reaction and continues until equilibrium is reached
Decreases
_______________
- The rate at a particular time during a reaction
- As with the most average rates, these rates decrease as the reaction progresses
Instantaneous rates
Most important instantaneous reaction rate is the ___________ rate
Initial rate
_______________
- allow estimation of chemical reaction rates as a function of changing reactant concentration, assuming a constant temperature
Rate laws
_______________ components
- must be determined experimentally
- Initial rates can be determined from initial reactant concentrations
- By using initial rates from several experiment, reactant orders are determined
- Known reaction rate in reactant order used to calculate value of K
Rate law components
_______________
- When simple differential rate laws for a single reactant decomposing into products are integrated over time, new relationships are obtained and relating concentrations of reactants to time
Integrated rate laws
_______________
- Time required for reactant concentration of a reaction to drop to half of its initial concentration
Half life
_______________ equation
- used to estimate the effect of temperature changes on a reaction rate constant (k)
Arrhenius equation
_______________ plot
- A graph of the natural log of rate constant versus inverse of the temperature in K
- Yields a straight line
Arrhenius plot
____________________ equation
- simplified equation that is used to estimate reactions Ea using rate constant data at 2 different temperatures
Two point Arrhenius equation
_______________ diagram
- shows potential energy of a reaction as it progresses
Reaction energy diagram
_______________
- sequence of elementary reaction steps (singular molecular event) that explains how reactants are transformed into products
- rate law for an elementary reaction is determined from its stoichiometry
Reaction mechanism
_______________
- step that limits how fast overall reaction can progress
- Elementary steps of a mechanism do not necessarily have same rate and often one step is slower & controls rate of overall process
Rate determining step
Correlating a reaction mechanism to a rate law —> mechanism must meet criteria :
- Elementary steps must __________ two overall balanced equation and cannot be fewer reactants or products than in balanced equation
- Elementary steps must be physically reasonable and most involved one or two species
- Mechanism must correlate with rate law and must support experimentally & independently determined rate laws
Add up
_______________
- Study of relationship between a chemical change and electrical work
Electrochemistry
_______________
- System that incorporates a redox reaction to produce electrical energy (spontaneous process) or utilize it (non-spontaneous process)
Electrochemical cell
_______________ reactions
- transfer of electrons between reactant atoms
Oxidation reduction reactions
_______________
- object that conducts electricity between the cell and surroundings
Electrode
_______________
- mixture of ions (usually an aqueous solution) that are involved in an electron flow process (redox reaction)
Electrolyte
_______________
- electrode where oxidation a half reaction takes place
- negative
Anode
_______________
- electrode where reduction half reaction takes place
- positive
Cathode
_______________ cell
- produces electrical current from a spontaneous redox reaction
Voltaic cell
_______________
- compartment were components of each of cells redox half reactions are housed
Half cell
_______________
- pathway by which counterions flow between the half cells while not allowing components to mix
Salt bridge
_______________ notation
- Oxidation half cell is on the left and reduction half cell is on the right
- components of cell appear in same order as half cells with electrodes on the outside
- Double lines, separate half cells and represent salt bridge
- Counter ions associated with the salt bridge are not shown
Voltaic cell notation
_______________
- potential difference between half cells
- Driving force for electron flow
Cell potential
____________ (SHE)
- Half cell potential cannot be measured directly, so a particular half cell is arbitrarily assigned potential of 0 V
- and all other half cell potential‘s are measured relative to this standard
Standard hydrogen electrode
E-cell values are used to predict redox reaction ____________
Spontaneity
E-cell > 0 reaction is _______________
Spontaneous
E-cell < 0 reaction is _______________
Nonspontaneous
_______________
- uses electrical energy to drive non-spontaneous redox reactions
Electrolysis
_______________ cell
- similar to voltaic cell that can drive nonspontaneous redox reactions
- Electrodes (oxidation at anode & reduction at cathode)
- Difference from voltaic cell is an external electrical voltage source
- Voltage source is positive terminal is connected to anode which draws electrons from anode & negative terminal is connected to cathode which supplies electrons to cathode
Electrolytic cell
