Question 5

The reaction of calcium carbonate (CaCO₃) and EXCESS dilute hydrochloric acid
(HCℓ) is used to investigate one of the factors that affects reaction rate. The balanced
equation for the reaction is:

The same mass of CaCO3 is used in all the experiments and the temperature of the
hydrochloric acid in all experiments is 40 °C.

The reaction conditions for each experiment are summarised in the table below

5.1 For this investigation write down the:

5.1.1 Dependent variable (1)

5.1.2 Independent variable (1)

The carbon dioxide gas, CO2(g), produced during EXPERIMENT A, is collected in a
gas syringe. The volume of gas collected is measured every 20 s and the results
obtained are shown in the graph below.

5.2 What can be deduced from the graph regarding the RATE OF THE
REACTION during the time interval:

5.2.1 20 s to 40 s (1)

5.2.2 60 s to 120 s (1)

5.3 Calculate the average rate (in cm³∙s^-1) at which CO2(g) is produced in the experiment. (3)

5.4 How will the volume of CO2(g) produced in experiment B compare to that
produced in experiment A? Choose from GREATER THAN, SMALLER THAN
or EQUAL TO. (1)

5.5 A graph is now drawn for experiment C on the same set of axes. How will the
gradient of this graph compare to the gradient of the graph for experiment A?
Choose from GREATER THAN, SMALLER THAN or EQUAL TO. (4)

Use the collision theory to fully explain the answer

5.6 Assume that the molar gas volume at 40 °C is 25,7 dm³∙mol-¹. Calculate the mass of CaCO₃(s) used in experiment A. (4)

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