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2023 O Level Chem P1 Q23 — Rate of Reaction Solution

Rate of Reaction 2023 O Level Pure Chemistry · Paper 1 · Q23

Question

Hydrogen peroxide decomposes to produce water and oxygen. The equation for this reaction is shown. 2H₂O₂ → 2H₂O + O₂. An experiment to study the rate of this reaction produces the results shown by curve X. Using the same volume of hydrogen peroxide, which changes to the reaction conditions could produce the results shown by curve Y? 1 increasing the concentration of hydrogen peroxide. 2 using a catalyst. 3 increasing the temperature of the hydrogen peroxide. Question diagram

Question diagram

A1 and 3
B1 only
C2 and 3
D2 only

Correct answer: C

Video Solution

Explanation

Answer: C. Curve Y reaches the same plateau as X (so the maximum moles of \(\text{O}_2\), and therefore the moles of \(\text{H}_2\text{O}_2\) that decomposed, are unchanged) but climbs to it more steeply (faster initial rate).

(1) Increasing the concentration of \(\text{H}_2\text{O}_2\) — but the stem fixes the volume of \(\text{H}_2\text{O}_2\). Higher concentration would mean more moles of \(\text{H}_2\text{O}_2\), giving more \(\text{O}_2\) — a higher plateau, not the same one. Inconsistent with curve Y. ✗

(2) Using a catalyst — speeds the reaction without changing the moles produced. Same plateau, steeper curve. ✓
(3) Increasing temperature — also speeds the reaction; the moles available to decompose are unchanged. Same plateau, steeper curve. ✓

So 2 and 3 only: option C.

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