Hydrogen peroxide decomposes slowly at room temperature to give water and oxygen. 2H2O2(aq) → 2H2O(l) + O2(g) The initial rate of this reaction can be increased by the addition of a metal oxide catalyst. A student is asked to investigate which metal oxide catalyst is best at increasing the initial rate of this reaction by using a method which involves the collection of oxygen. The student is provided with the following metal oxides: copper(II) oxide, iron(III) oxide, manganese(IV) oxide, nickel(II) oxide and titanium(IV) oxide. The student is also provided with an excess volume, of a known concentration, of aqueous hydrogen peroxide and any laboratory equipment needed.

1. (a)(i)State the independent variable.[1]
2. (a)(ii)State the dependent variable.[1]
3. (b)State two variables that would need to be controlled. 1 2[2]
4. (c)Draw a labelled diagram of the assembled apparatus that could be used to carry out these experiments. The apparatus should allow the accurate recording of the oxygen produced.[3]
5. (d)(i)What measurements need to be recorded during the course of each experiment to allow the initial rate to be determined?[1]
6. (d)(ii)How is the initial rate determined using these measurements?[1]
7. (e)How can the student ensure that the results are reliable?[1]
8. (f)Suggest an alternative method to investigate these reactions which does not include the collection of gas.[1]
9. (g)Once the reaction has finished, how can the student demonstrate that the metal oxide has not been affected by the reaction?[2]
10. (h)When aqueous hydrogen peroxide is stored there is a small hole in the lid of the bottle. Suggest why this is necessary.[1]

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