Board-style MCQs and past-paper numericals in the BIEK / Sindh Board pattern. Tap an option to check yourself instantly. Solved questions are at the bottom.
Multiple-choice questions
Solved numericals & self-assessment (past papers)
pH of 0.01 M HCl and 0.01 M NaOH
HCl: [H⁺] = 0.01 = 10⁻² → pH = 2
NaOH: [OH⁻] = 0.01 → pOH = 2 → pH = 14 − 2 = 12
[H⁺] of a solution with pH = 4.5
[H⁺] = 10⁻ᵖᴴ = 10⁻⁴·⁵ = 3.16 × 10⁻⁵ mol/dm³
Titration: concentration of an acid
25 cm³ of HCl needs 20 cm³ of 0.1 M NaOH for neutralisation.
moles NaOH = 0.1 × 20/1000 = 0.002 = moles HCl (1:1)
[HCl] = 0.002 ÷ (25/1000) = 0.08 M
Buffer pH (Henderson–Hasselbalch)
A buffer has [CH₃COONa] = 0.2 M and [CH₃COOH] = 0.1 M, pKa = 4.74.
pH = pKa + log([salt]/[acid]) = 4.74 + log(0.2/0.1) = 4.74 + 0.30 = 5.04
Identify the conjugate base of H₂SO₄ and the conjugate acid of NH₃
Conjugate base of H₂SO₄ (lose H⁺) = HSO₄⁻
Conjugate acid of NH₃ (gain H⁺) = NH₄⁺