The problem states that zinc reacts with excess dilute hydrochloric acid, meaning zinc is the limiting reactant. The same mass of zinc is used in all experiments. The reaction time is the time taken

Step 1: Analyze the given information for Question 13.
The reaction is $\text{Zn(s)} + 2\text{HCl(aq)} \to \text{ZnCl}_2(\text{aq}) + \text{H}_2(\text{g})$.
The problem states that zinc reacts with excess dilute hydrochloric acid, meaning zinc is the limiting reactant. The same mass of zinc is used in all experiments. The reaction time is the time taken for the reaction to be completed (i.e., all zinc to react).

13.1 Experiment 1 and experiment 5 are compared. Write down the independent variable.

• Experiment 1: Concentration = 2.0 mol/dm³, Volume = 200