General Chemistry Flashcards
Atomic number
number of protons, if this changes you have a new element
Mass number
total mass of protons plus neutrons
subtract atomic number from mass number to find the number of neutrons in a molecule
What are isotopes used for?
track chemical reactions
How to name elements with more than one cation (transition metals)
use roman numerals
use -ous prefix for smaller charge and -ic prefix for greater charge
Naming oxyanions
hypo- -ite (2 less)
-ite (1 less)
-ate (normal)
per- -ate (more)
Pauli Exclusion Principle
no two electrons in an atom can have exactly the same four quantum numbers
Ranking of orbitals, shells and subshells
Shells are periods (n=1, 2, 3 …)
Subshells are s,p,d,f (n=1 only has the s subshell)
Orbitals are within the subshells and can hold 2 electrons (s can have 1 orbital, p can have 3 orbitals)
Aufbau principle
electrons fill lower orbitals first
Hund’s rule
fill orbitals half full first
(everyone wants own seat on the bus)
Group 1 elements
alkali metals
highly reactive
good cations
Group 2 elements
alkaline earth metals
Group 6 elements
chalogens
Group 7 elements
halogens
often found as diatomic molecules to form complete valence shell
Trends with Zeff
increases across periodic table (more protons with no new shell electrons)
decreases down periodic table (more protons but also more shell electrons to block Zeff)
Trends with radius
decreases across periodic table since Zeff is increasing
increases down periodic table
Trends with electronegativity
increases across periodic table
decreases down periodic table
same as Zeff
Are anions bigger or smaller than neutral atom?
bigger
more electrons = more electrostatic repulsion
Are cations bigger or smaller than neutral atom?
smaller
less electrons = less repulsion and greater Zeff
Ionization energy
amount of energy to remove electron from atoms
first electron always the easiest to remove
Which bonds can lead to H-bonding?
-FH -OH and -NH bonds
especially electronegative bonds
Combustion reaction
a compound burns in the presence of oxygen
highly exothermic
Does a reaction with a +H make the surrounding area warmer or colder?
+H indicates an endothermic reaction
takes heat from the environment to drive reaction
makes the surrounding area colder
Does increasing temperature speed up all reactions?
No. Only speeds up endothermic reactions where heat acts like another reactant
Neutralization reaction
Acid + Base –> H2O + Salt
Intramolecular forces
ionic bonds, covalent bonds, metallic
bonds within a molecule
Intermolecular forces in order of increasing strength
London dispersion forces Dipole-dipole interactions H-bonds Ionic-dipole interactions Ionic interactions
What is a stronger bond ionic or covalent?
ionic
Do larger or smaller molecules have greater London dispersion forces? Why?
Larger molecules. More probable for a temporary random dipole to form
what is a biological example of an intermolecular force?
peptide hormone temporarily associating with a membrane receptor
Which atoms do not follow the octet rule?
Sulfur and phosphorous can have expanded octet
Hydrogen is stable with 2 valence e
Helium has max 6 valence e
Boron has max 5 valence e
Be has max 4 valence e
Which molecule has greater bond angles water or methane?
Methane
Water has two lone pairs that make it’s bonds squish together
Methane can be in the tetrahedral formation with 109.5º between its bonds
Difference between trigonal planar and trigonal pyrimidal?
trigonal planar has no lone pairs
When do we see sp hybridization?
triple bonds
When do we see sp3 hybridization?
Four bonds
Ex: in a methyl group
When do we see sp2 hybridization?
ex: a carbonyl group
What is the hybridization of the central carbon in CO2?
sp
has two regions of electron density
If pH is greater than pKa what happens?
since the solution is more basic, the molecule is in conjugate base form and deprotonated
If pH is less than pKa what happens?
since the solution is more acidic, the molecule is in conjugate acid form and protonated
What are the common diatomic molecules?
Have No Fear Of Ice Cold Beer
hydrogen, nitrogen, flourine, oxygen, iodine, chloride, bromine
What do most oxidizing agents generally include?
Cr and O
What is an example of a weak oxidizing agent?
PCC
What are examples of reducing agents?
NaBH4, NaH, LiAlH4
When can reducing agents be biochemically used?
to break disulfide bonds
What is hydrogen’s general oxidization state?
+1
What is oxygen’s general oxidization state?
-2
What is the carbonyl carbon’s oxidization state in carboxylic acid?
+3
When do redox reactions occur?
when at least one specie’s oxidization state changes
When glucose is converted into two molecules of pyruvate during glycolysis what happens?
the carbon is oxidized
How do titrations work in general?
1) take a known volume of solution and use add another substance of a known concentration to it
2) when substance starts changing color, you know that moles of the added substance = moles of substance of interest
3) can set M1V1 = M2V2, where V2 is how much volume of the known substance was added
4) solve for concentration of the unknown substance
What is true at the equivalence point of a titration?
at the equivalence point moles are equal
*the vertical line portion
What is true at the half equivalence point of a titration?
pH = pKa
*middle of horizontal line
What are titrations used for?
to find an unknown concentration in solution
What is the change in enthalpy equal to?
the heat of a reaction
What are standard conditions?
25ºC, 300K, 1 atm
What is the enthalpy of formation of Cl2?
0 kJ/mol
no heat needed to produce pure elements
Do you need energy to create bonds?
no
energy is released when bonds are formed
Do you need energy to break bonds?
yes
need to put energy in to break bonds
What is Keq equal to?
products / reactants
What happens when Keq is >1?
products are favored
∆G is negative (spontaneous) in the forward direction
What happens when Keq is <1?
reactants are favored
∆G is positive (nonspontaneous) in the forward direction
What happens when Keq =1?
We are at equilibrium at ∆G = 0
What is Q?
the equilibrium at any point
What happens when Q
have too many reactants, equilibrium shifts to the products
What happens when Q>Keq?
have too many products, equilibrium shifts to the reactants
Is the thermodynamic or kinetic product favored at high temperatures?
the thermodynamic product
have enough energy to overcome activation barrier and create the more stable product
Is the thermodynamic or kinetic product favored at low temperatures?
the kinetic product
don’t have enough energy to form the more thermondynamically stable product so we make the less stable, kinetic product
Relationship between pressure and boiling point
lower pressure means a lower boiling point because it is easier for liquid molecules to “spread out” into gas phase
analyte
compound/molecule being investigated
Avogadro’s number
6e23 atoms (or units) per one mole
What are ways (5) that an enzyme can catalyze a reaction?
1) stablize the T-state
2) change the orientation of a molecule
3) weaking bonds within reactants
4) increase frequency of collisions
5) donate ED to the reactants
heterogenous catalysts
in a different phase than the reactants
often a solid phase catalyze will absorb liquid/gas reactants
homogenous catalysts
in the same phase as the reactants
In endothermic reactions, are the products or the reactants higher in energy?
the products
have to add energy to get to the products
rate law
mathematical expression for the relationship between reactant concentrations and the rate of a reaction
What is the example of a zero order reaction?
an enzyme that is saturated
the rate is not dependent on the reactants, dependent on the enzymes since saturated
What rates are important for determine a rate law?
the initial rates of a reaction
How do you find Zeff?
subtract the shell electrons from the number of protons
What signifies a better oxidizing agent?
more likely to reduce
Why does reduction happen at the cathode?
a molecule can gain electrons from the negatively charged cathode
What should not be included in Keq?
pure liquids and solids
Does temperature affect equilibrium of exothermic reactions?
Yes
temperature is a product in exothermic reactions
so decreasing the temperature, will shift the reaction towards the products
If you only have the total sample mass can you determine the molecular formula?
no
can only find the empirical formula
need the molecular mass to find the molecular formula
How can you find the yield of a product using stoich?
1) convert starting grams to moles
2) divide moles of regants by coefficient
3) after step 2, the smaller number is the limiting reagant
4) determine how many moles of product you will have
5) solve for total mass of product
examples of amorphous solids
glass, gel, plastic
have less structure than crystalline solids
molecular solids
a type of crystalline solid held together by intermolecular forces
network solids
a type of crystalline solid held together by covalent bonds
viscosity
resistance of liquid to flow
higher viscosity = slower flow
what is surface tension created by?
intermolecular forces between water molecules at surface
cohesive forces versus adhesive forces
cohesive forces are between the same molecules
adhesive forces are between different molecules
formula and units for pressure
pressure = force/area
Pa = N/m2
fusion
solid to liquid phase transition
sublimation
solid to gas phase transition
deposition
gas to solid phase transition
What is happening on flat lines of a heat curve?
on the flat lines a phase transition is happening. so look at change in enthalpy
What is happening on the sloped lines of a heat curve?
adding heat to same phase
use Q=mc∆T formula
Balmer series
hydrogen emission lines corresponding to transitions from higher levels to n=2
in the visible spectrum
Lyman series
hydrogen emission lines corresponding to transitions from higher levels to n=1
in the UV wavelengths
Order of wavelengths from shortest to largest
gamma rays X rays UV visible light infrared microwave radiowaves
What does kinetic molecular theory tell us?
gas particles are in constant motion and exhibit perfectly elastic collisions
2 assumptions of ideal gases
1) gas particles have no volume
2) gas particles experience no attraction or repulsion
When do gases behave more like “ideal gases”?
at high temperatures, high volumes, and low pressures
What units does temperature need to be in when working with gases?
Kelvin
K = ºC + 273
Molar volume
1 mole of gas occupies 22.4 L at STP
STP versus thermodynamic conditions
STP (gas): T=273K
Thermodynamic: T= 298K
If we have two ideal gases of the same moles at STP, will the two gases occupy the same volume? Why?
yes, because ideal gases act as if they do not have their own volume
Do real gases have greater or lower pressure/volume than ideal gases at STP?
real gases have lower pressure/volume at STP since real gases can attract each other, resulting in lower volume
Do real gases have greater or lower pressure/volume than ideal gases at extreme conditions?
greater pressure/volume at extreme conditions
What would effuse first CO2 or H2?
H2 since it is smaller
Graham’s law predicts this
If you decrease the volume of a reaction vessel, how would the equilibrium shift?
decreased volume means increased pressure
shift to side of reaction with fewer moles of gas to decrease pressure
If you decrease the pressure of a reaction vessel, how would the equilibrium shift?
shift to side of reaction with more moles of gas to increase pressure
Arrhenius acid
acids dissociate to form H+ ions
Arrhenius base
bases dissociate to form OH- ions
Bronsted-Lowry acid
an acid is a proton donor
Bronsted-Lowry base
a base is a proton acceptor
Lewis acid
an acid is an electron acceptor
Lewis base
a base is an electron donor
Difference between Bronsted-Lowry and Lewis definitions
Bronsted-Lowry definition refers to protons
Lewis definition refers to electrons
Amphoteric species
can act as acids or bases
Kw
equilibrium constant for the auto-ionization of water
What is the formula for Kw?
Kw = [H3O+][OH-]
What does Kw equal at standard conditions?
1*10^-14
What happens to Kw if we raise the temperature?
Kw increases
auto-ionization of water is an endothermic process
What do salts do to the boiling point of water?
they increase the boiling point
What do salts do the freezing point of water?
they decrease the boiling point
If the vapor pressure of a liquid decreases, what happens to the boiling point?
it increases since it takes more heat to get the vapor pressure up to the atmospheric pressure
What are the four colligative properties?
1) vapor pressure reduction
2) boiling point elevation
3) freezing point depression
4) osmotic pressure
What is vapor pressure?
pressure gas exerts above the liquid phase
Vapor pressure change formula
P = XaPa
As the mol fraction of solvent decreases what happens to the solvent’s vapor pressure?
it decreases since there are less moles of solvent compared to moles of solutes
What is the boiling point elevation formula?
∆Tb=iKbm
What is the freezing point elevation formula?
∆Tb=iKfm
Molarity in water versus molality in water
Molarity in pure water is roughly equal to the molality
What values have to be used for colligative properties?
molality and the number of dissolved particles!
What is the standard reduction potential measured in?
Volts
If the reduction potential is more positive?
the reduction is more likely to happen spontaneously
What is true of all electrochemical cells?
anode is site of oxidation
cathode is site of reduction
electrons move from anode to cathode
How to remember anode versus cathode
An Ox Red Cat
Galvanic cell
spontaneous redox reaction is used to generate a positive potential difference that drives a current
Eºcell must always be positive
Cathode and anode in galvanic cell
Cathode is positive since electrons move towards it spontaneously and anode is negative
Daniell cell
a common galvanic cell
electrons pass through a wire
salt bridge allows spectator ions to travel between the half cells and balances charge
Concentration cell
a type of galvanic cell
solutions aren’t separated
electrodes made out of the same material
2 regions have a concentration difference
Electrolytic cells
electrical input is used to drive a nonspontaneous redox reaction
Eºcell is negative
Anode and cathode in galvanic cell
Cathode is negative since electrons do not spontaneously go to it
anode is positive
What type of cells are biological cells like SDS page?
electrolytic
negative charges move towards positive anodes
Rechargable batteries
when discharging, battery acts like a spontaneous galvanic cell
when recharging, battery acts like a nonspontaneous electrolytic cell that requires energy
Nernst equation
helps account for how electric potential of a cell is affected by temperature and concentration of reactants
E’cell = Eºcell - 0.06/z*log(Q)
Relationship between Q and E’cell
As Q increases and products increase, E’cell decreases and is less spontaneous
Relationship between ∆G and Eºcell
∆G= -nFEºcell
