A student investigates the reaction of large pieces of calcium carbonate with dilute hydrochloric acid at 25°C. The hydrochloric acid is in excess.

1. (a)Complete the equation for this reaction by adding state symbols. CaCO₃(......) + 2HCl(......) → CaCl₂(aq) + H₂O(......) + CO₂(g)[2]
2. (b)Fig. 3.1 shows the volume of carbon dioxide gas released as the reaction proceeds. [Figure 3.1]
3. (b)(i)Deduce the volume of carbon dioxide gas released after 40 seconds. volume _________________________________________ cm³[1]
4. (b)(ii)The student repeats the experiment using the same mass of smaller pieces of calcium carbonate. All other conditions stay the same. Draw a line on the grid in Fig. 3.1 to show how the volume of carbon dioxide changes when smaller pieces of calcium carbonate are used.[2]
5. (c)The student repeats the experiment at 20 °C. All other conditions stay the same. Describe and explain, using collision theory, how the rate of reaction differs when a temperature of 20°C is used.[2]
6. (d)A sample of carbon dioxide is put into a gas syringe. The end of the gas syringe is then blocked so that no gas can escape. Explain, using kinetic particle theory, why increasing the pressure in the gas syringe decreases the volume of gas when the temperature stays the same.[1]

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