Chem Olympiad

6 Strong Acids

Hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), hydrobromic acid (HBr), hydroiodic acid (HI), and perchloric acid (HClO4), which completely dissociate in water.

Strong bases

Group 1 hydroxides, Heavy group 2 hydroxides (Ca(OH)₂, Sr(OH)₂, Ba(OH)₂)

Ammonium (NH4) produces an ______ solution

acidic

Small highly charged metal ions will make an _______ solution

acidic

Always soluble

Group 1 cations: Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ammonium: NH₄⁺, Nitrates: NO₃⁻, Acetates: CH₃COO⁻ (aka C₂H₃O₂⁻), Perchlorates: ClO₄⁻

Halides (Cl⁻, Br⁻, I⁻) are usually soluble except with

Ag⁺, Pb²⁺, Hg₂²⁺

Sulphates (SO₄²⁻) are usually soluble except with

Ba²⁺, Sr²⁺, Pb²⁺, Ca²

Carbonates (CO₃²⁻) are usually insoluble except with

Group 1, NH₄⁺

Phosphates (PO₄³⁻) are usually insoluble except with

Group 1, NH₄⁺

Hydroxides (OH⁻) are usually insoluble except with

Group 1 (soluble)

Ca²⁺, Sr²⁺, Ba²⁺ (slightly soluble but strong bases)

Sulfides (S²⁻) are usually insoluble except with

Group 1

Group 2

NH₄⁺

Beer’s Law

A = Ebc
A = absorbance, E = molar absorptivity, b = path length, c = concentration

Ionic solid

cations & anions, ionic bonds, NaCl, F2O3, brittle, conductor when molton/aqueous, BP: 200-2500

Metallic solid

metal atoms, metallic bonds, Cu, Zn, Na, malleable/ductile, conductor, BP: 500-3000

Network covalent solid

non-metal atoms, covalent bonds, Cgraphite, Cdiamond, SiO2, SiC2, very hard, insulator, BP: 1600-3800

Molecular solid

molecules of covalent compounds, IMFs, H2O, CO2, C12H22O11, I2, variable hardness, insulator, BP: <200

Ka for weak acid

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

Kb for weak base

[BH+][OH-]/[B]

Kw

equal to Ka • Kb, 1×10^-14

Coulomb's law (lattice energy)

q1q2/r

crystal structure density equation

p = Z • M / Na • a³
p = density, Z = formula units per cell, M = molar mass, Na = avogadros number, a = edge unit of cell

formula units per type of cell

primitive: 1, body-centered: 2, face centered: 4

nm

10^-7cm

pm

10^-10 cm

um (weird u with down thing)

10^-6 cm

density

D = m/V

mass/volume

mole fraction equation

Xi = n1/nT

equation for average molecular speed

Vrms = sqrt(3RT/M)

comparing rate of effusion based on molar mass

rate1/rate 2 = sqrt(M2)/ sqrt(M1)

first law of thermodynamics

ΔU=q+w​
internal energy change = heat + work

Gibbs free energy equation (enthalpy and entropy)

ΔG=ΔH−TΔS​

Gibbs free energy (from K at equilibrium)

ΔG∘=−RTlnK​

Gibbs free energy at nonstandard state

ΔG = ΔG° + RT lnQ

Van’t Hoff Equation

lnK=(−ΔH/R)(1/T)​+ΔS/R
Slope = (−ΔH/R)

Clausius–Clapeyron (For vapor pressure at different temperatures​)

ln(P2/​P1​​)=(−ΔHvap/R​​)(1/T2​​−1/T1​)

Heat capacity

q=mcΔT

q= energy transferred, m = mass, c = specific heat capacity, T = temperature

Energy required to change temperature

Phase change entropy

ΔS=ΔH/T

Enthalpy (total heat content)

H=U+PV
U = internal energy, P = pressure, V = volume

1st order reaction

ln[A]t - ln[A]0 = -kt, ln[A] vs time is a line

2nd order reaction

1/[A]t - 1/[A]0 = +kt, 1/[A] vs time is a line

0th order reaction

rate = k, [A] vs time is a straight line

1st order half-life

t1/2 = ln2/k

2nd order half life

t1/2 = 1/k[A]0

0th order half life

[A]0/2k

Radioactive decay

ln(A0/At) = -kt (follows first order)

Henderson-Hasselbalch (calculating pH of buffer solution)

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

de Broglie wavelength formula

λ = h / (m v) where λ is the wavelength, h is Planck's constant, m is the mass, and v is the velocity of the particle.