WEAK ACID · HA
Ethanoic acid
Moles HA0.1 mol
FranklyChemistry
Weak Acid & Buffer pH Calculator
Equilibrium reasoning,
not just an answer.
not just an answer.
MODERNISED TEACHER TOOL
Calculate pH and see the equilibrium assumptions.
Weak acidEthanoic acid, CH₃COOH
pKₐ4.759
CH₃COOH(aq) ⇌ H⁺(aq) + CH₃COO⁻(aq)
The salt supplies A⁻. The weak acid supplies HA. Because both are in the same final solution, their concentration ratio equals their mole ratio.
1
Use the equilibrium expression[H⁺] = Kₐ × n(HA) ÷ n(A⁻)
2
Find [H⁺]7.134 × 10⁻5 mol dm⁻³
3
Take −log₁₀[H⁺]pH = 4.147
CONJUGATE BASE · A⁻
Sodium ethanoate
Moles A⁻0.02439 mol
Buffer pH4.147Check: pH = pKₐ + log₁₀(n(A⁻)/n(HA)) = 4.147