Chemistry 3

Question 1

oxidation state

Answer 1

any elemental atom: 0
Fl: -1
H w/ a metal: -1
H: +1
O: -2
O in peroxides: -1
Group V: -3
Group VI: -2
Group VII: -1

Question 2

electrical potential (E°)

Answer 2

tell us the degree to which a species wants e-

positive E° → more likely to be reduced than H ions

negative E° → less likely to be reduced than H ions

E° values assigned are relative reduction potential of that species compared to hydrogen half cell: 2H+ + 2e → H2 (E° = 0 V)

Question 3

cell potential

Answer 3

half-reactions always come in pairs → one oxidation and one reduction

***don’t use stoichiometry → one mole of x has same reduction potential as two moles of x

Question 4

galvanic cell / voltaic cell

Answer 4

cathode = + and reduction
anode = - and oxidation

cell potential always positive

can be created using any two metals, regardless of reduction potentials → e- will flow from species with lower reduction potential to species with higher reduction potential

Question 5

electrolytic cell

Answer 5

cathode = - and reduction
anode = + and oxidation

*** external voltage applied → species with the lower reduction potential will be reduced

cell potential always negative

sum of externally applied voltage and the negative E° cell must be positive

Question 6

concentration cell

Answer 6

special type of galvanic cell

same electrodes and solution are used in both beakers

positive cell potential if there is a difference in the molarities of the two solutions

E° cell always = 0

Question 7

Nernst equation

Answer 7

E = E° - (0.06/n)*log[lower]/[higher]

Question 8

free energy and chemical energy

Answer 8

∆G° = -nFE°

n = number of moles of e- transferred in balanced redox reaction
F = Faraday's constant

Question 9

Faraday’s constant

Answer 9

9.6 x 10^4 C/mol

charge on one mole of electrons

Question 10

ideal gas law

Answer 10

PV = nRT

R = 0.0821 (Latm)/(molK) or 8.314 J/(mol*K)

Question 11

ideal gas assumptions

Answer 11

gas molecules have negligible volume compared to the volume occupied by the gas

all intermolecular forces between gas molecules are negligible

*** gas molecules = no volume and no intermolecular forces

Question 12

STP

Answer 12

standard temperature and pressure
P = 1 atm
V = 22.4 L
n = 1 mole
T = 273 K (0 °C)

Question 13

standard conditions

Answer 13

P = 1 atm
concentration  = 1 M
T = 298 K (25 °C)

Question 14

absolute zero

Answer 14

a theoretical temperature where all molecular motions cease

Question 15

combined gas law

Answer 15

P1V1 / T1 = P2V2 / T2

Question 16

real gases

Answer 16

greatest deviation between ideal gas behavior and real gas behavior occurs:
1) temperature is extremely low → actual size of molecules becomes comparable to distance in between them → real gas will occupy greater volume than expected by equation

2) pressure is extremely high → intermolecular interaction between gas molecules becomes more prevalent → real gas will produce smaller pressure than expected by equation

PV/nRT > 1 → deviation from ideal gas law due mostly to molecular volume assumption

PV/nRT < 1 → deviation from ideal gas law due mostly to intermolecular forces assumption

Question 17

Van der Waals euation

Answer 17

increased intermolecular attractions → decrease pressure in real gases

increased molecular volume → increased volume in real gases

Question 18

effusion / diffusion

Answer 18

E1 / E2 = √MW2 / √MW1

Question 19

vapor pressure

Answer 19

partial pressure of the gaseous form of a liquid that exists over that liquid when the liquid and gas are in equilibrium

↑ temperature → ↑ vapor pressure

addition of a non-volatile solute → ↓ vapor pressure

addition of volatile solute → depends on vapor pressure of volatile solute

Question 20

Raoult’s law

Answer 20

vapor pressure w/ a non-volatile solute: Vp = XVp°
X = mole fraction of the pure solvent
Vp° = vapor pressure of the pure solvent

vapor pressure w/ a volatile solute: Vp = Vpsolvent + Vpsolute = (Xsolvent)(Vp°solvent) + (Xsolute)(Vp°solute)

Question 21

Henry’s law

Answer 21

the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas over that liquid

Question 22

gas solubility

Answer 22

increased temperature → decreased solubility

increasing vapor pressure of gas X over a liquid increases the solubility of gas X in that liquid

polar and non-polar gases easily form homogenous mixtures

Question 23

boiling point elevation

Answer 23

boiling point of a liquid is elevated when a non-volatile solute is added

∆T = kb m i 
kb = constant
m = molality
i = # ions formed per molecule

Question 24

freezing point depression

Answer 24

freezing point of a liquid is depressed when a non-volatile solute is added

∆T = kf m i
kf = constant
m = molality
i = # ions formed per molecule

Question 25

osmotic pressure

Answer 25

π = iMRT
i = # of ions formed per molecule
M = molarity
R = gas constant
T = temperature in K

Question 26

molarity

Answer 26

moles solute / L solution

Question 27

molality

Answer 27

moles solute / kg solvent

*** doesn’t change with temperature

Question 28

ppm

Answer 28

(mass solute / total mass solution) (10^6)

*** just a measure of mass percent

ppm = mg/kg = mg/L

Question 29

normality

Answer 29

of moles of equivalents / L solution

Question 30

Ksp

Answer 30

leave out pure liquids/solids → Ksp equations only have numerator

temperature is the only thing that changes Ksp

Ksp can only be observed in a saturated solution → saturation is the point at which dissolution reaction has reached equilibrium

Question 31

ion product / solubility product

Answer 31

same relationship to Ksp as Q does to Keq

Question 32

soluble compounds

Answer 32

nitrate (NO3 -), ammonium (NH4 +), all alkali metals

Question 33

insoluble compounds

Answer 33

*** unless paired with one of the always soluble compounds

carbonate (CO3 -2), phosphate (PO4 -3), sliver (Ag), mercury (Hg), lead (Pb)