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Chemistry Formula Reference

Essential formulas for CSCA exam

Basic Concepts

NameFormulaUnit
Amount of substancen = N / Nₐmol
Molar massM = m / ng/mol
Avogadro constantNₐ = 6.02 × 10²³/mol
Molar concentrationc = n / Vmol/L
Molar volume (STP)Vₘ = 22.4 L/molL/mol
Mass fractionw = m溶质 / m溶液 × 100%%
Densityρ = m / Vg/mL

Stoichiometry

NameFormulaUnit
Conservation of massm反应物 = m生成物-
Gas density (STP)ρ = M / 22.4g/L
Average molar massM̄ = Σ(nᵢMᵢ) / Σnᵢg/mol
Theoretical yield产率 = 实际产量/理论产量 × 100%%

Thermochemistry

NameFormulaUnit
Enthalpy changeΔH = H生成物 - H反应物kJ/mol
Hess's LawΔH总 = ΔH₁ + ΔH₂ + ...kJ/mol
Heat of combustionQ = nΔHckJ
Heat of neutralizationΔH ≈ -57.3 kJ/molkJ/mol

Chemical Equilibrium

NameFormulaUnit
Equilibrium constantKc = [C]ᶜ[D]ᵈ / [A]ᵃ[B]ᵇ-
Pressure constantKp = pCᶜpDᵈ / pAᵃpBᵇ-
Reaction quotientQc vs Kc 判断方向-
Conversion rateα = (n₀ - n) / n₀ × 100%%

Chemical Kinetics

NameFormulaUnit
Reaction ratev = Δc / Δtmol/(L·s)
Rate lawv = k[A]ᵐ[B]ⁿ-
Arrhenius equationk = Ae^(-Ea/RT)-
Half-life (1st order)t₁/₂ = ln2 / ks

Electrochemistry

NameFormulaUnit
Faraday constantF = 96500 C/molC/mol
Electrolysis massm = MIt / nFg
Cell EMFE = E⁺ - E⁻V
Nernst equationE = E° - (RT/nF)lnQV

Acid-Base Equilibrium

NameFormulaUnit
pH definitionpH = -lg[H⁺]-
pOH definitionpOH = -lg[OH⁻]-
Ion product of waterKw = [H⁺][OH⁻] = 10⁻¹⁴-
pH + pOHpH + pOH = 14 (25°C)-
Acid dissociationKa = [H⁺][A⁻] / [HA]-
Buffer equationpH = pKa + lg([A⁻]/[HA])-

Solubility Equilibrium

NameFormulaUnit
Solubility productKsp = [M⁺]ᵐ[A⁻]ⁿ-
Solubilitys = ⁿ√(Ksp)mol/L
Precipitation conditionQsp > Ksp 则沉淀-

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