General Chemistry II Formulas

just kill me now

when solving a heating/cooling curve problem, what formulas do you use? (the q ones)

q = mcΔT for the original equation
q = nΔH for the combined states

m = mass

c = specific heat capacity (water = 4.184)

ΔT = change in temperature (in KELVINS)

n = moles

ΔH = change in enthalpy

cell density formula (think perovskite)

P = Z(MM)/(6.022E23)(a³)

P = cell density

Z = atomic number

MM = molar mass

a = side length

how many atoms are in a face centered cubic unit cell?

4 (there are atoms present in the corners and faces of the cube → 8(1/8) + 6(1/2) = 4)

how many atoms are in a body centered cubic unit cell?

2 (there are atoms present in the corners and center of the cube → 8(1/8) + 1 = 2)

how many atoms are in a simple cubic unit cell?

1 (there are atoms only in the corners of the cube → 8(1/8) = 1)

What do you use when you have to calculate how much a gas dissolves in a liquid (hint: Henry’s Law)?

C = kP

C = concentration

k = solubility constant

P = partial pressure of the gas

what is the formula for morality?

M = n/L

n = moles

L = volume (in LITERS)

what is the formula for molality?

m = n_solute/kg_solvent

what is the formula for mole fraction (X)?

X = n_solute/n_solution

what is the formula for ppm?

ppm = (mass_solute/mass_solution) x 1,000,000

1,000,000 = 10⁶

what is the formula for ppb?

ppb = (mass_solute/mass_solution) x 1,000,000,000

1,000,000,000 = 10⁹

What equations do you use when dealing with vapor pressure and mole fraction? (hint: Raoult’s Law)

Vapor Pressure: P_solvent = (X_solvent)(P°_solvent)

Change in Vapor Pressure: ΔP = P_solvent - P_solvent = (X_solute)(P°_solution)

What equation do you use for measuring boiling point elevation?

ΔT = iK_bm

i = van’t Hoff factor (ex: NaCl i = 2 and CaCl₂ i = 3)

K_b = constant of the solvent

m = molality

What equation do you use for measuring freezing point depression?

ΔT = iK_fm

i = van’t Hoff factor (ex: NaCl i = 2 and CaCl₂ i = 3)

K_f = constant of the solvent

m = molality

What formula do you use to find osmotic pressure?

π = iMRT

π = osmotic pressure (in ATM)

i = van’t Hoff factor (ex: NaCl i = 2 and CaCl₂ i = 3)

M = molarity

R = 0.08206

T = temperature (in KELVIN)

What formula do you use to find the enthalpy of sublimation (ΔH_sub)?

ΔH_sub = ΔH_fus + ΔH_vap

What is the half-life formula for the zero order rate law?

t = [A_o]/2k

What is the half-life formula for the first order rate law?

t = 0.693/k

What is the half-life formula for the second order rate law?

t = 1/k[A_o]

What equation do you use when you’re given the K_p and K_c?

K_p = K_c(RT)^Δn

What are all of the pH equations?

pH = -log[H⁺] and pOH = -log[OH^-]

[H⁺] = 10^-pH and [OH^-] = 10^-pOH

pH + pOH = 14

Kw = KaKb = [H3O⁺][OH^-]

When looking at buffer capacity and titrations (before eq. pt.) what equation should you use? (hint: Henderson Hasselbach)

pH = pK_a + log(base/acid)

How do you calculate K_a, K_b, and K_sp?

K_a = [H⁺]² / [HA]

K_b = [OH^-]² / [A^-]

K_sp = [products]/[reactants]

How do you calculate K_a and K_b during salt hydrolysis?

producing H3O⁺: K_a = [A^-][H3O⁺]/[HA]

producing OH^-: K_b = [BH⁺][OH^-]/[B]

What formulas do you use for Gibbs Free Energy?

ΔG = ΔH - TΔS

ΔG = ΔG° + RTln(Q)

ΔG° = -RTln(k)

What is the formula to find cell potential (E_cell)?

E_cell = cathode - anode

What are the Nernst equations related to E_cell?

E_cell = E°_cell - (RT/nF)ln(Q)

E_cell = E°_cell - (0.0592/n)log(Q)

What are the Nernst equations related to ΔG, K_eq, and E_cell?

F = 96485 c

What is the galvanic cell notation?

anode | anode solution || cathode solution | cathode