Chemistry 0620 · IGCSE · Rate of reaction

Rate of reaction — practice question

A student carried out an investigation into how magnesium carbonate reacts with an excess of dilute hydrochloric acid. $\text{MgCO}_3 + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{CO}_2 + \text{H}_2\text{O}$ The reaction rate may be determined by tracking how the mass of the reaction mixture falls with time. The graph shows the results.
(a)[1]

Find the mass of the reaction mixture at 58 seconds.

(b)[2]

Which point on the graph, A, B, C or D, showed the fastest rate of reaction? Use the graph to justify your answer.

(c)[1]

If $0.42$ g of magnesium carbonate produces $120\ \text{cm}^3$ of carbon dioxide, determine the volume of carbon dioxide made when $1.26$ g of magnesium carbonate reacts fully.

(d)[2]

What effect do the following have on the rate of this reaction? • Lowering the concentration of the acid. • Cutting the magnesium carbonate into smaller pieces.

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