Potassium bromate(V) reacts with potassium bromide and sulfuric acid to form potassium sulfate, bromine and water according to the following equation. KBrO3(aq) + 5KBr(aq) + 3H2SO4(aq) → 3K2SO4(aq) + 3Br₂(aq) + 3H2O(l) A student is investigating how the rate of this reaction is affected by changing the concentration of the reactants in turn. This is done by keeping the total volume of mixture constant and adding different, small volumes of each reagent. The reaction produces bromine which is orange in colour. The student times the reaction and then determines the rate as 1/time. The rate equation for the reaction is of the form: rate = k[KBrO3]ˣ[KBr]ʸ[H₂SO₄]ᶻ k is the rate constant for the reaction and x, y and z are the respective orders of the reaction for each reagent. The student carried out the experiment and obtained the following data. Table 3.1 mixture [KBrO3] /mol dm⁻³ [KBr] /mol dm⁻³ [H2SO4] /mol dm⁻³ rate of reaction /s⁻¹ A 0.025 0.125 0.075 0.059 B 0.050 0.125 0.075 0.117 C 0.025 0.250 0.075 0.118 D 0.025 0.125 0.150 0.235 E 0.050 0.250 0.150 0.941

1. (a)(i)Suggest how the student might time the reaction and judge the end point of the reaction for each mixture.[1]
2. (a)(ii)By comparing the data for the mixtures deduce the values of x, y and z.[2]
3. (b)The student carried out each reaction using a boiling tube (capacity 50 cm³) and varied the concentration by adding different volumes of each reagent. For example, in mixture A, 5.0 cm³ of KBrO3(aq) is required. Name a suitable piece of apparatus which could be used to measure this volume.[1]
4. (c)Suggest why the reagents are heated to the same temperature before mixing.[1]
5. (d)The solution of sulfuric acid used in each mixture was of concentration 0.150 mol dm⁻³. This acid was prepared from a solution of concentration 1 mol dm⁻³. Briefly describe how to make the more dilute solution, stating the capacity of any apparatus used.[2]