A-LevelChemistryReaction kineticsMay/June 2010Paper 1 Q131 Mark
Na2S2O3 reacts with dilute HCl to give a pale yellow precipitate. If 1 cm³ of 0.1 mol dm⁻³ HCl is added to 10 cm³ of 0.02 mol dm⁻³ Na2S2O3 the precipitate forms slowly. If the experiment is repeated with 1 cm³ of 0.1 mol dm⁻³ HCl and 10 cm³ of 0.05 mol dm⁻³ Na2S2O3 the precipitate forms more quickly. Why is this?
AThe activation energy of the reaction is lower when 0.05 mol dm⁻³ Na2S2O3 is used.
BThe reaction proceeds by a different pathway when 0.05 mol dm⁻³ Na2S2O3 is used.
CThe collisions between reactant particles are more violent when 0.05 mol dm⁻³ Na2S2O3 is used.
DThe reactant particles collide more frequently when 0.05 mol dm⁻³ Na2S2O3 is used.
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The correct answer is D. This question tests the candidate's understanding of reaction kinetics within the Chemistrysyllabus. The examiner's mark scheme requires...
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