The rate of reaction between a metal and bromine can be studied using the apparatus shown below.
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A piece of metal, for example iron, was weighed and placed in the solution as shown above. The metal was removed at regular intervals and each time it was washed, dried and weighed. It was then replaced in the solution and the reaction continued.<br>From the results (mass of metal and time), the rate of the reaction can be calculated.<br>a) i) How would the rate change if more of the piece of metal was in the solution? Explain your answer.
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Explain the change in rate.<br>b) In a reaction between a solid and a solution, the rate may depend on the speed of stirring. Describe how you could find out if the rate of the reaction between solid iron and bromine solution depends on the speed of stirring.<br>c) Iron has two oxidation states so it can form two ions, $$\mathrm{Fe^{2+}}$$ and $$\mathrm{Fe^{3+}}$$. How could you test a solution to find out which ion is present? Outline the test, and give the results for both ions.<br>d) In the reaction between iron and bromine, iron atoms change into iron ions and bromine molecules change into bromide ions.<br>i) Which of these changes is a reduction? Explain your choice.<br>ii) If iodine was used instead of bromine, predict how the rate of the reaction would change (increase, decrease or stay the same). Give a reason for your answer.