Chemistry Flashcards
How many molecules are in a mole?
6.02x10^23
1 AMU = ____ kg
1.66x10^-27 kg
What are diamagnetic and paramagnetic orbitals?
Diamagnetic - contains only spin paired electrons
Paramagnetic - 1 or more electrons are not spin paired
Note: odd number of electrons must be paramagnetic but even number of electrons can be either one
Quantum number table
Page 247
Degenerate orbitals
Orbitals that have identical energies (ie 2p orbitals)
How are electrons placed into orbitals?
From lowest to highest energy
What is an excited state electron?
Not a ground state configuration
Contains the same number of electrons as the element and does not violate filing rules (number of e per subshell)… Fill diff orbitals
Isoelectronic ion
Ion that has same number of electrons as another
Periodic trends
- Electronegativity
- Atomic radius
- Ionization energy
- Metallic character
- Electron affinity
- F>O>N>Cl>Br>I>S>C~>H»>Fr
- Decreases L-R, increases T-B
- Increase L-R
- Decreases L-R
- Increases L-R
Ionization energy and bonds
Difference in E
E>1.7 = ionic bond
1.7>E>0 = polar covalent
0 = nonpolar covalent
Equation for a quanta
[]E=hf Or []E=h(c/wavelength) h is planck's constant c is speed of light f is frequency of electromagnetic radiation used to increase energy of the electron
Heisenberg uncertainty principle
Position and momentum cannot be determined simultaneously at all times for an election and therefore it’s orbit is not spherical (p 251)
- combined with schrodinger wave equation, gives rise to probability density orbitals
De broglie hypothesis
Any particle with momentum should have a wavelength
Wavelength=h/p or w=h/mv
h is planck’s constant
P 252
Radioactive decay process (what is it)
Decay type-symbol-change in mass number-change in atomic number
-antimatter electron?
Page 252/253
Einsteins equation for nuclear biding energy and mass deficit
E=mc^2
Types of intermolecular bonds by strength
ii>id>dd>iid>did>idid (LDF)
H bonding is from ii to did
What must be present for h bonds to occur
What does h bonding do to bp?
H bonded to F,O, or N
Lone pair of electrons
-increase it
Ammonium
NH4+
Nitrate
NO3-
Carbonate
CO3^2-
Sulfate
SO4^2-
Phosphate
PO4^3-
Strength of repulsive forces in VSEPR model
Lone pair-lone pair>LP-BP>BP-BP
1BP 0LP
Linear
2bp, 0lp
Linear
3lp, 0bp
Trigonal planar
4bp, 0lp
Tetrahedral
3bp, 1lp
Trigonal pyramidal
2bp,2lp
Bent
1bp,3lp
Linear
5bp,0lp
Trigonal bipyramidal
4bp,1lp
Seesaw
3bp,2lp
T-shaped
2bp,3lp
Linear
6bp,0lp
Octahedral
5bp,1lp
Square pyramidal
Equation for moles ad mola mass, etc
n=m/MM
MM is molar mass
m is mass
n is moles
Does the limiting reagent limit the rate of the reaction?
No, it limits the extent… Ie how much products will form
- see how to calculate limiting reagent p 280
Explain oxidation rules
- Group 1A +1
- Group 2A +2
- Group 3B +3
- Fluorine -1
- Oxygen -2 (-1 if peroxide)
- Hydrogen +1 when bonded to nonmetals, -1 bonded to metals
Oxidizing reducing agent and oxidant reductant and oxidized reduced
How to balance oxidation/reduction reactions
Page 281
What is kinetics
Study of chemical reactions focusing on SPEED and MECHANISM.
Irrelevant - amount of products formed, equilibrium amount of products/reactants, thermodynamics, stoichiometry
What determines the reaction mechanism that prevails in a chemical reaction?
Concentrations Pressure Temperature Absence or presence of a catalyst Also microscopic reversibility
Unimplecular vs bimecular process
An elementary process having one or two reactant molecules
Activation energy and rate-determining step
The rate determining step is the slowest step in the reaction due to highest activation energy.
For any mechanism the step with the highest Ea is the slowest step.
How to calculate reaction rate
For aA + bB -> cC + dD
Rate = -[][A]/a[]t = -[][B]/b[]t = [][C]/c[]t = [][D]/d[]t
Note the - sign!!
How to calculate rate due to concentration
From aA + bB -> cC + dD Rate = k[A]^x[B]^y Overall order = x+y x and y not related to coefficient k is temperature dependent and does not change with time - see p 288 for info about K
How to convert log
logx=y
x=10^y
What do catalysts do?
Alter activation energy of reaction
Allows reaction to occur via alternate pathway
Inhibits (inhibitory catalyst) or promotes reaction (slows it down or speeds it up)
See p 290 for homo vs heterogenous catalysts
What can change a reactions equilibrium constant?
A change in temperature and in some cases pressure and volume
Position of equilibrium is changed in other cases (Le Chatelier’s principle) to fix the change made but Keq stays the same.
Note: increase in T, p or v does not necessarily mean increase in Keq
Equilibrium constant equation
Keq = [C]^c[D]^d/[A]^a[B]^b In molarity (M) Pure liquids and pure solids don't appear in equation because they tend to have concentration of 1M
Finding equilibrium constant for gasses
Kp=Kc(RT)^[]n
Kp is equilibrium constant calculated from partial pressures
Kc is Keq calculated from molar concentrations
R gas constant
T absolute temp
n change in total number of moles of gas from reactants to products
Ratio of products to reactants and Keq
Keq»1 products favoured
Keq=1 neither
Keq«1 reactants favoured
Reaction quotient
Q = (C)^c(D)^d/(A)^a(B)^b
Brackets indicating concentrations
Relationship between Q and Keq
Q>Keq products in excess, decrease in products and increase in reactants as reaction approaches eq
Q=Keq at equilibrium
Q<Keq reactants in excess, increase in products and deceease in reactants as reaction approaches eq
What would be he equilibrium for the reverse reaction?
Keq(reverse) = 1/Keq(forward)
How to determine Keq for the reactions
aA+bB->cC+dD = K1
cC+dD->eE+fF = K2
aA+bB->eE+fF
Keq = K1(K2)
How does addition or removal of product or reactant affect equilibrium? Addition of non-reactive product?
Le Chatelier’s principle (pg 300)
Note this does not chance value of Keq!!
If unreactive substance is added, no change in pp or Keq, but increase in total pressure
Describe pH and equilibrium wrt:
HA H+ + A-
Increase H+ lowers ph, shifts equation left and decreases A- (the conjugate base)
Decrease H+ raises ph, shift equation right and increases A-
What happens when volume is increased or decreased in a reaction?
If volume is decreased (p increased) reaction is pushed in direction with less moles of gas
Opposite for increased v
If both sides contain equal moles of gas, no change in eq if pressure is changed
-wrt adding a gas, a nonreactive gas will have no affect on equilibrium and adding a reactive gas will follow le chataliers principle
Explain the effects of temperature on equilibrium
Determines whether it’s endothermic or ectothermic and then use Le Chatelier’s principle
Open vs closed vs isolated system
Open - energy and matter exchanged
Closed - energy only
Isolated - neither
Note universe = surroundings + system
Name the state and nonstate functions
Nonstate - work and heat
State - everything else
Note: nonstate functions depend on the path and therefore deal with the concepts of reversibility and irreversibility (ie can’t unable a cake)
-p 309
What are the 2 principal ways a system can gain or lose energy?
By heat transfer or by work
What is the equation for work in thermodynamics?
W=P[]V
P is pressure
V is internal volume change by system
Note: this is mechanical work done by expanding gasses - reversible process always related than irreversible process (like heat)
Describe positive and negative heat and work
- Q system (+Q surroundings) when heat is transferred from system to surroundings (and vice versa)
- W when work is done by system, +W when it’s done on system
What is greater (wrt heat and work) reversible or irreversible process?
Q - reversible process>irreversible process (whether given off or gained)
W - performed by reversible process>performed by irreversible process (does not matter if work is done on system or surroundings)
Internal energy of a system
Total energy within a system (kinetic and potential energy) expressed in relative terms []U=Q-W and U=Q+W U is change in internal energy Q is heat GAINED by system W is work done by or on system
What is entropy? When is it increasing?
Measure of disorder Entropy increases when: 1. Temp increases 2. In a reaction if the reaction produces more product molecule than it contained reactant molec. 3. Pure liquids or solids form solutions 4. S(universe) always increases
Equation for enthalpy and it positive/negative values
Converting between Kalvin and degrees
0 C = 273.15 K
Heat of formation
Enthalpy required for the formation of one mole of that substance from its elements
0 for all elements in their naturally occurring state
Standard heat of formation
Heat of formation in standard conditions (T=298.15K, p=1atm)
STP (standard temperature and pressure)
T=273.15, p=1atm
Heat of reaction
[]H^o={Hf products- {Hf reactants
Endothermic is +
Exothermic is -
Why is heat of formation of liquid water different from that of gaseous water?
Extra enthalpy is given off in he Hf of liquid water as result of transition from higher to lower energy state.
Known as enthalpy of liquefaction or enthalpy of condensation.
Gibbs free energy
[]G=[]H-T[]S T is constant All thermodynamic quantities refer to the system Measure of energy available to that system for the performance of useful work -[]G is exergonic (spont. Forward) \+[]G is endergonic (non-sp. forward) 0 means reaction is at equilibrium Know the chart!! []H - T []S Endothermic - high (+) = - Exothermic - high (-) = +
3 laws of thermodynamics
- For any isolated system, energy is constant ([]U=Q+W)
- Entropy is always increasing - entropy in the forward direction does not equal entropy in the reverse direction - heat is never completely converted to useful work in a cyclic process (it’s possible in a linear one) ie if the forward process does so, the reverse will not
- Absolute zero is unattainable
Know how to draw reaction diagrams
Activation energy, transition state, reaction intermediate, sn1/sn2 reactions, rate determining step, catalyst
Pg 320
Note: limiting reagent is not necessarily rate determining step!
Because LR has little to do with kinetics …it just gets used up first because there is less of it, it doesn’t effect the speed
Does a catalyst affect []H or []G?
No, it just changes the activation energy. It also does not change equilibrium. It lowers the transition state.
Finding []G^o at equilibrium
[]G=[]G^o + RTlnQ But []G at equilibrium is 0 so: []G^o = - RTlnKeq []G^o is at 298K and 1atm R is universal gas constant T is temperature Q is the equation from before (calculated at diff temperatures) \+ []G^o favours reactants - []G^o favours products 0 []G^o favours neither
Heat of solution
Enthalpy change that occurs when a solute dissolves in a solvent.
- exothermic solvation (heat released)
+ endo, heat absorbed
Henry’s law (solubility of gases in a liquid solvent)
p=kC
C is solubility of gas
k is Henry’s law constant for the gas
p is partial pressure of gas solute over the solution
Note: solubility of gas is proportional to pressure of gas above the solution
How to know if solid is soluble in liquid
If the solid attains:
>0.05M - soluble
<0.01M - insoluble
Btw .05 and .01 - moderately soluble
Molarity
M=moles of solute/liters of solution
Normality
Used almost exclusively for acids and bases
N=(n of potential H+ or OH-)/liters of solution
Molality
m=(moles of solute)/(kg of solvent)
Mole fraction
Usually used with gases
Xs=(moles of solute)/(total miles of solution)
Molarity of water
55M
Equilibrium constant equation for solubility (solubility constant)
Keq=Ksp=[A]^a[B]^b
From: AaBb(s)aA(aq)+bB(aq)
Ksp will never have a denominator because it is a pure liquid/solid and thus does not appear in Ksp
Examples of weak electrolytes
Weak acids and bases
Examples of strong electrolytes
Salts of alkali metals and ammonium
Some salts of alkaline earth metals, all nitrates, chlorates, perchlorates, and acetates
What substances are solvated (not dissociated)
Methanol, ethanol, glucose and fructose
Van’t Hoff factor
(i) how many species a substance dissociates into
i(NaCl)=2 i(CaCl2)=3
Glucose=1
Raoult’s law (how vapor pressure of a pure liquid is lowered by the addition of a nonvolatile solution)
pi = Xi(pi^o) pi is vapor pressure of solvent i above the solution i Xi is the mole fraction of solvent I pi^o is vapor pressure of pure solvent i or Psoln=Xsolv(P*solv) In the case of a nonvolatile solute dissolved in a solvent P 339/360
What happens to boiling point of a pure liquid when nonvolatile solute is added?
It increases []Tb=Kb(i)(m) []Tb is boiling point elevation Kb is bp elevation constant i is Van't Hoff factor for solute m is molality of solute P 340
What happens to freezing point of a pure liquid when a solute is added?
It decreases []Tf=Kf(i)(m) []Tf is freezing point depression Kf is fp depression constant i is Van't Hoff factor for solute m is molality of solute Page 341
Osmotic pressure
Pressure exerted on the membrane when equilibrium is reached
O = nRT/V or O=iMRT
n is number of moles of particles dissolved
R is the gas constant
T is the absolute temperature
V is the volume of the solution
Air pressure conversions
P=F/A=Pa 1atm= 760mmHg= 760torr= 1.013x10^5Pa
One mole of ideal gas at STP occupies what volume?
STP= 0C at 1atm
22.4L or 0.0224 cubic meters
(Note that this value is 25C in the standard thermodynamic state)
5 premises of kinetic molecular theory
For IDEAL gas behaviour
- Gases are composed of molecules in rapid, random, translational motion (Ek=1/2mv^2)
- These particles undergo perfectly elastic collisions
- Space occupied by particles is negligible
- There are no attractive or repulsive forces btw particles
- Ek=3/2nRT -n being for moles of gas particles
- if deviation from any of these laws occurs, it is not an ideal gas
Boyle’s law
PV=constant
or
P1V1=P2V2
For ideal gases under constant temperature and with constant moles
Charles’s law
V/T=constant or V1/T1=V2/T2 or V1T2=V2T1 For ideal gases under constant n and P
Gay-Lussac’s law
For ideal gasses under constant n and V P/T=constant or P1/T1=P2/T2 or P1T2=P2T1
Combined gas law
For ideal gases at constant n PV/T=constant or P1V1/T1=P2V2/T2 or P1V1T2=P2V2T1
Avogadros hypothesis
For ideal gases at constant P and T V/n = constant or V1/n1=V2/n2 or V1n2=V2n1
Ideal gas law/gas constant
R=PV/nT
or
PV=nRT
R is in J/mol•K
What conditions favour ideal gases?
Low pressure, high temperature
High P and low T lead to deviations from ideal gas law
What are the deviations from ideal gas law wrt P and V?
- excluded volume
Actual pressure is always less than or equal to pressure calculated by ideal has law
Actual volume occupied by a gas is always grater than or equal to the volume calculate by ideal gas law
- the actual volume of the gas is equal to the volume of the container plus the excluded volume (volume of gas molecules themselves)
Vanderwalls equation
(P+an^2/V^2)(V-nb)=nRT
What does this signify?
Adjustment for real gasses wrt ideal gas law
Ideal P = realP + an^2/V^2
Ideal V = realV - nb
The sections after the +&- in each equation is the correction factors
Law of partial pressure
Ptotal=Pa+Pb Pt=(na+nb)RT/V Pa=Xa(Pt) Xa=na/nt Xa is the mole fraction of gas a
Graham’s law of diffusion (effusion)
v1^2/v2^2=m2/m1
or
v1/v2=_/(m2/m1)
v is velocity, m is mass
-the lighter molecule will have a higher velocity (rate of diffusion) than the heavier one
-diffusion is movement of gas through space and effusion is movement if gas under pressure through a small hole
The conversion from solid to gas is called
Sublimation
The direct conversion from gas to solid is called
Deposition
What is the formula for heat absorbed by a system when it isn’t undergoing a phase change?
q=mc[]T q is heat a absorbed m is mass of substance c is specific heat capacity (cal/g•C) - water is 1 cal/g•C []T is temp change IN C!!
Formula for heat of a phase change
q=m[]H
q is heat
m is mass
[]H is the enthalpy of the phase change in units of energy per mass
How to find C (specific heat capacity for exact amount of substance being considered) from a phase change diagram
Slope=1/C
mc=C and 1/slope=mc
P 375
How to find heat of fusion for phase change diagram
Length of horizontal line = []Hfus•m
m is mass of substance
Plot a phase diagram
Pg 379
What is the diff for a pt diagram of water?
Ph 380
Draw a pt diagram for a substance with more than one solid form
Pg 381
What happens if the triple point of a substance occurs at pressure >1atm?
It will sublimate under atmospheric conditions and appropriate temp change (example co2 at 216.8 K and 5.11 atm)
Describe he critical point
Beyond this temperature, there is no way to distinguish btw liquid and gas (no matter what the pressure is)
Defined at critical temp and critical pressure
Equilibrium expression for auto ionization of water
Kw = [H+][OH-] = 1x10^-14
and
[H+] = [OH-] = 1x10^-7
This Kw value is valid for any aqueous solutions at 25C (not just pure water)
Formula for pH/pOH of a solution
pH=-log[H+] pOH=-log[OH-] and pH+pOH=14 (-log[H+])+(-log[OH-])=(-logKw)
How to transform log values
[H+]=n•10^-x
if n=1, pH = x
if n=3.17, pH=x-0.5 (bc root 10=3.17)
if n is higher or lower than 3.17, use x-0.5 and evaluate (pg 389)
Arrhenius, bronsted-Lowry, and Lewis definition of acids/bases
- Substance that produces H+ or OH- ions respectively
- Proton donor or accepter respectively
- Electron acceptor or donor respectively
- water is neither acid or base in Arrhenius terms but in BL it can be either an acid or a base
Define strong acid/base
Strong A/B fully undergo forward dissociation in aqueous solution. Dissociation equilibrium lies entirely to the right and reverse reaction doesn’t occur to an appreciable degree. No appreciable amount of original A/B left in solution.
Examples of strong acids (6)
HCl hydrochloric acid HBr hydrobromic acid HI hydroiodic acid HNO3 nitric acid HClO4 perchloric acid H2SO4 sulfuric acid
Examples of strong bases (6)
LiOH lithium hydroxide NaOH sodium hydroxide KOH potassium hydroxide RbOH rubidium hydroxide (NH2-) amide ion (H-) hydride ion
What makes acids more acidic?
Electron withdrawing groups, which stabilize their conjugate bases (making the conjugate base less willing to protonate and thus, weaker)
Acid/base ionization constant expression
HA + H2O H3O+ + A-
Ka = [H3O +][A-]/[HA]
Because water is a pure liquid.
Same thing for base
What is the pKa/Ka relationship?
pKa=-logKa and pKb=-logKb
Strong a/b have large Ka/Kb and small pKa/pKb values
Weak a/b have small Ka/Kb and small pKa/pKb values
2 other equations used for any acid/bad pair in dilute aqueous solution
KaKb=Kw
pKa + pKb = 14
For any conjugate acid/base pair in a dilute aqueous solution
Hendeson Hasselbalch equation
Useful in titrations
pH = pKa + log[A-]/[HA]
pOH = pKb + log[BH+]/[B]
What happens when you mix a strong acid and a strong base?
They neutralize. This process is always ectothermic. If there is excess acid or base, solution will be acidic or basic respectively and not completely neutral.
HA + BOH -> H2O + B+ + A-
Creates water and salt
What is the equivalence point?
The point at which the acid has been neutralized by the base added. Exactly one equivalent of base has been added for one equivalent of acid. This is 7 for strong acid/base titration.
What is the equivalence point for strong/weak a/b?
Equivalence point of weak acid titrated with strong base will be pH >7. For weak base titrated with strong acid, <7.
Recall the equivalence point is when equal amounts of a/b have been added. This effect is due to the excess of conjugate a/b, with that of strong a/b act as spectators (unreactive salts).
What is the half-equivalence point?
Point when the amount of a/b added is exactly half of the base needed to reach equivalence point.
At this point, referring back to HH equation, the fraction =1 and therefore:
pH=pKa or pOH=pKb
What is log 1?
0
Where is the buffering region an what is always found within it?
It is the first part of the weak/strong a/b titration curve and always includes the half-equivalence point.
What is a polyprotic acid and what does its titration curve look like? What are indicators?
Pg 404/405
A more concentrated buffer is stronger or weaker?
Stronger
What is a buffer composed of?
A weak acid/base and it’s corresponding conjugate
Describe the pH and pKa of a buffer
For a buffer, pH=pKa
How do you write redox couples?
Oxidized form/reduced form
Ie: Cu++/Cu for the reaction:
Cu++ + 2e- -> Cu^0
Think of the redox couples as similar to acid/conjugate base pairs
Describe the anode and cathode
- electrode and inert electrode
- direction of current
Cathode is the electrode at which reduction occurs
Anode is the electrode at which oxidation occurs
Electrons flow from anode to cathode and therefore current moves from cathode to anode
-p 415
How to calculate electromotive force and cell emf
-what can alter emf?
Emf is E^o at standard conditions of 1M for solutes, 1atm for gasses, and 25C. Standard half cell is for H+
Cell emf is the sum of all the half reactions. Don’t multiply it by stoihiometric coefficient!
P 418
How to draw cell diagrams
Oxidation reactant, oxidation product || reduction reactant, reduction product
Fe2+(aq), Fe3+(aq) || Mn2+(aq), Mn7+(aq, 0.5M)
If conditions are not standard, concentration may be shown in parenthesis
Note that with a salt bridge, (Pt) is added to each end to represent the platinum, unreactive conductor (electrodes)
Explain a galvanic cell
Redox reaction is spontaneous
The cell creates e- flow
Oxidation is at anode & reduction is at cathode
Cathode is the positive electrode (anode is -)
Electrons flow from anode to cathode
Describe electrolytic cell
Redox reaction is nonspontaneous
The cell requires e- flow
Oxidation is at anode & reduction is at cathode
Cathode is the - electrode (anode is positive)
Electrons flow from anode to cathode
Explain what a concentration cell is
Page 425
Equation relating []G to E^o
[]G^o=-nFE^o
n is moles of e-
F is Faradays constant
[]G=-nFE for nonstandard conditions
Nernst equation
E = E^o - 2.303(RT/nF)logQ R and F are constants also E^o = (0.0592/n)logKeq For equilibrium under standard conditions (298K and 0E)
What direction is the arrow pointing in a dipole moment?
The head points towards the negative charge
What is a formal charge?
The overall charge on a molecule (ie +1). Partial charge is the dipole moment, the uneven distribution of electrons.
Energy and bond formation
Breaking bonds require energy, forming bonds release energy
What is (x)(2x)^2?
4x^3
Explain how to represent where atomic mass, atomic weight, charge, and atomic number are located
P 242
What is a period/group?
Periods are horizontal and groups vertical
Periods = same principle quantum number (shell number)
Groups = same valence electrons and similar physical properties
Describe Pauli exclusion principle, hunds rule, and the aufbau principle
P.e. = no electron in any one atom will have the same 4 quantum numbers as any other electron in that atom H.r. = no 2 electrons will become spin paired unless there are no empty orbitals at that energy level A.p. = how electrons are placed Ito orbitals from lowest to highest energy
What are representative (main block elements) vs transition metals? What are actinides/transuranium elements?
251
What are the 5 main types of reactions?
P 275
Describe how to make hybridized orbitals
Chapter 33 (731)
Describe the types of isomerism/properties
Chapter 34 (731)
Describe energy wrt breaking and forming bonds
Breaking bonds requires an input of energy and forming bonds an output
What is microscopic reversibility?
The principle that all elementary steps are reversible in exactly the reverse manner (even though the overall reaction is not exactly reversible)
Solubility general info
P 329
Look at solubility rules
P 332
What is solubility affected by?
Temperature, common ions, pH
What are colligative properties?
P 338
Pressure depends on what?
Number of collisions (increase with increasing number of molecules or decreasing volume)
Velocity of colliding gas molecules (increases with temperature)
Mass of colliding gas molecules
Under which conditions are the solid/liquid/gas phase favoured? How are each of these phases characterized?
P 369
Heat of fusion, vaporization and sublimation (endo or exothermic)
P 371
Relate heat and phase changes to kinetic energy and temperature
P 372
What is a calorie? What is the specific heat of liquid water?
The amount of heat energy that must be supplied to one gram of liquid water at 25C to raise the temperature of the water by 1C
-specific heat of water is 1cal/g•C
What is a ligand?
Lewis bases that form bonds with transition metals
How to use reduction potential chart
416
