A student investigated the rate of reaction between calcium carbonate chips and excess dilute hydrochloric acid:
CaCO3(s)+2HCl(aq)→CaCl2(aq)+H2O(l)+CO2(g) \text{CaCO}_3\text{(s)} + 2\text{HCl(aq)} \rightarrow \text{CaCl}_2\text{(aq)} + \text{H}_2\text{O(l)} + \text{CO}_2\text{(g)} CaCO3(s)+2HCl(aq)→CaCl2(aq)+H2O(l)+CO2(g)The volume of carbon dioxide gas collected was measured over time. The student plotted a graph of the volume of carbon dioxide collected in cm3\text{cm}^3cm3 against time in seconds.
To determine the rate of reaction at t=45 st = 45\text{ s}t=45 s, a tangent was drawn to the curve at that point. The tangent line passes through the coordinates (15 s,24 cm3)(15\text{ s}, 24\text{ cm}^3)(15 s,24 cm3) and (75 s,63 cm3)(75\text{ s}, 63\text{ cm}^3)(75 s,63 cm3).
Calculate the rate of reaction at t=45 st = 45\text{ s}t=45 s. Give your answer to 2 significant figures and include the units.
Explain, in terms of collision theory, why the rate of reaction decreases and eventually becomes zero.
26 exam-style questions on AQA GCSE Chemistry 6.1 Rate of reaction, covering 6.1.1 Calculating rates of reactions, 6.1.2 Factors which affect the rates of chemical reactions, 6.1.3 Collision theory and activation energy, and 6.1.4 Catalysts. Each one has a worked solution and a mark scheme showing where the marks go.