OAT General Chemistry equations

Change in internal energy

ΔU = Q - W by system

ΔU = Q in - Q out + W on - W by

Half life

A = A0(1/2)^n

t(1/2) = 0.693/k

Energy of electron

E = -Ry/n^2

E = hc/lambda = -Ry(1/ni^2 - 1/nf^2)

Number of electrons in shell n

2n^2

Zero order reaction

Rate = k

First order reaction

Rate = k[A]

Second order reaction

Rate = k[A]^2

Rate = k[A][B]

Rate = k[B]^2

Gibbs free energy

ΔG = ΔH - TΔS

Standard free energy

ΔG0= -RT lnKeq

Keq > 1 = forward

Keq

Density of gas

d = P(molar mass)/RT = m/V

Dalton's Law of Partial Pressures

Ptotal = P1 + P2 + P3...

P1 = X1Ptotal

Boyle's Law

P1V1=P2V2

Like boil, squeezing pimple (P and V)

Charle's Law

V1/T1=V2/T2

Charlie Brown on TV (T and V)

Avogardo's Law

V1/n1 = V2/n2

V and n are directly proportional

Volume of one mole of gas at STP

22.4 L

Comparative ideal gas equation (gets rid of R)

PV/PstpVstp = nT/nstpTstp

stp = standard temperature + pressure

Molality

moles of solute/kg of solvent

Density can be helpful here

Dilution

M1V1=M2V2

Solubility Rules

See review notes

Vapor pressure depression

ΔPsoln = Xsolute*Psolvent (STP)

More solute = less surface area available for evaporation

Boiling point elevation

ΔTb = iKbm

Since boiling occurs when Pvapor = Psolvent, lowering Pvapor by adding solute increases boiling point

Freezing point depression

ΔTf = iKfm

Solute interrupts ability of solvent to form solid crystals, lowering freezing point

Osmotic pressure

π = iMRT

Pressure needed to prevent osmosis

Factors affecting solubility in water

Increase temperature: solubility of solid solute increases and solubility of gas solute decreases

Acid dissociation constant

Ka = [H+][A-]/[HA]

Base dissociation constant

Kb = [HB+][OH-]/[B]

Autoionization of water

Kw = [H+][OH-] = 1*10^-14

Log shortcut (p function)

If [anything] = m*10^-n

Then p[anything] = (n-1).(10-m)

Titration equivalence point

VaNa = VbNb

Normality equation

N = M(equivalents/mol)

Henderson-Hasselbalch equation

pH = pKa + log [A-]/[HA]

pOH = pKb + log [HB]/[B]

Electromotive force (emf)

Ecell° = Ecathode° - Eanode°

Faraday's Law of Electrolysis

It = nF

Gibbs free energy (related to emf)

ΔG = -nFEcell°

ΔG = -RTlnKeq

nFEcell° = RTlnKeq

R = 8.314

Alpha decay

Lose He: - 2 protons and neutrons

Only decay that changes atomic mass

Beta minus decay

Electron emission

One of atom's neutrons turns into a proton by emitting an electron

atomic number increases by 1

Electron capture

Beta minus decay in reverse: proton to neutron

Beta plus decay

Positron emission

atomic number decreases by 1

Gamma decay

Emission of high energy photon

no changes to atom's atomic structure

Fraction remaining after n half-lives

(1/2)^n

Fraction of nuclei decayed after n half-lives

1 - (1/2)^n