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Date November 2016 Marks available 3 Reference code 16N.2.hl.TZ0.3
Level HL Paper 2 Time zone TZ0
Command term Deduce and Explain Question number 3 Adapted from N/A

Question

Sodium thiosulfate solution reacts with dilute hydrochloric acid to form a precipitate of sulfur at room temperature.

Na2S2O3 (aq) + 2HCl (aq) → S (s) + SO(g) + 2NaCl (aq) + X

(i) Using the graph, explain the order of reaction with respect to sodium thiosulfate.

(ii) In a different experiment, this reaction was found to be first order with respect to hydrochloric acid. Deduce the overall rate expression for the reaction.

Markscheme

i

first order
«because» [Na2S2O3] is «directly» proportional to rate of reaction « 1 t »

Do not accept “linear” for M2.

 

ii

rate = k[Na2S2O3][HCl]

Examiners report

[N/A]

Syllabus sections

Additional higher level (AHL) » Topic 16: Chemical kinetics » 16.1 Rate expression and reaction mechanism
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Additional higher level (AHL) » Topic 16: Chemical kinetics
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