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Question 4

An analyst studies the kinetics of the reaction between magnesium ribbon and hydrochloric acid, HCl(aq)\text{HCl(aq)}HCl(aq). Under the experimental conditions, the reaction is first-order with respect to HCl(aq)\text{HCl(aq)}HCl(aq).

  • The analyst first performs the reaction using 0.450 mol dm−3 HCl(aq)0.450\text{ mol dm}^{-3}\text{ HCl(aq)}0.450 mol dm−3 HCl(aq). The measured initial rate of reaction is 3.15×10−4 mol dm−3 s−13.15 \times 10^{-4}\text{ mol dm}^{-3}\text{ s}^{-1}3.15×10−4 mol dm−3 s−1.
  • The analyst then takes a different sample of the same 0.450 mol dm−3 HCl(aq)0.450\text{ mol dm}^{-3}\text{ HCl(aq)}0.450 mol dm−3 HCl(aq), dilutes it with distilled water, and measures the pH of this diluted acid to be 1.851.851.85.
  • The reaction is repeated under identical temperature and surface area conditions using this diluted acid.

Determine the initial rate of the reaction with the diluted acid. Give your answer to 3 significant figures.

[4]
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How fast? Questions

  1. A Level
  2. /Chemistry
  3. /How fast?

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