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)
Find the order from experimental data
When [A] is doubled (at constant [B]), the rate quadruples; when [B] is doubled, the rate doubles.
Order in A: rate ∝ [A]² → second; order in B: rate ∝ [B]¹ → first.
Rate law = k[A]²[B]; overall order = 3
Calculate the rate constant (first order)
A first-order reaction has rate = 6×10⁻³ mol dm⁻³ s⁻¹ when [A] = 0.3 M.
k = rate / [A] = (6×10⁻³) / 0.3 = 0.02 s⁻¹
Effect of a 30 °C temperature rise
If the rate doubles per 10 °C, a 30 °C rise multiplies the rate by 2 × 2 × 2 = 8 times.
Units of k for a second-order reaction
rate = k[A]² → k = rate / [A]² = (mol dm⁻³ s⁻¹)/(mol dm⁻³)² = mol⁻¹ dm³ s⁻¹
Why does a catalyst not change the equilibrium position?
A catalyst lowers Ea for the forward AND reverse reactions equally, so it speeds both directions. It reaches the same equilibrium faster but the position (and K) is unchanged.