Post-UTME Chemistry 2018 Objective — Question 8

Question 8 of 21 from the Post-UTME Screening (Post-UTME) Chemistry 2018 Objective paper, with the correct answer and a full explanation.

Na2S2O3(aq) + 2HCl(aq) -> 2NaCl(aq) + H2O(l) + SO2(g) + S(s). The time required for a white deposit of S to appear in the action above was measured at various temperatures. These results suggest that the rate of reaction

A. increases for a 10C rise in temperature
B. decreases for a 10C rise in temperature
C. is unaffected by a change in temperature
D. doubles for a 10C rise in temperatureCorrect

Explanation

The classic thiosulphate-acid 'clock reaction' shows reaction time roughly halving (rate roughly doubling) for each 10C rise in temperature.

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