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How Fast? The Rate of Chemical Change · Paper 2 — Free Chemistry SL Practice Questions

1MasterySAQ-SFactors affecting reaction rates: Concentration, temperature, surface area, catalysts5 marksPaper 2~8 min

Zinc granules react with sulfuric acid:

\text{Zn(s)} + \text{H}_2\text{SO}_4\text{(aq)} \rightarrow \text{ZnSO}_4\text{(aq)} + \text{H}_2\text{(g)}

A student places

5.0\,\text{g}

of zinc granules into

100.0\,\text{cm}^3

0.50\,\text{mol dm}^{-3}

\text{H}_2\text{SO}_4\text{(aq)}

25\,°\text{C}

and measures the volume of hydrogen gas collected every

30\,\text{s}

. The reaction is slow at first, then becomes faster, and finally slows down until it stops.

(a)

Explain why the reaction rate initially increases even though the concentration of acid is decreasing. [2 marks]

(b)

The student repeats the experiment using the same mass of zinc in the form of a single large piece. Describe two differences in the volume-of-gas versus time graph compared to the original experiment. [2 marks]

(c)

Explain, using collision theory, why these differences occur. [1 mark]

Solutions

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