A piece of magnesium was added to 100 cm3 of an aqueous acid. The time taken for the metal to react completely was measured. This experiment was repeated using different aqueous acids. The same volume of acid was used in each experiment and the pieces of magnesium used were identical. In one experiment the reaction was carried out at a different temperature. Explain the following in terms of collision rate between reacting particles. (i) Why is the rate in experiment C slower than the rate in experiment A?

[2] (ii) Why is the rate in experiment B faster than the rate in experiment A?


[2] (iii) Why is the rate in experiment D faster than the rate in experiment A?


[3] d) The soluble salt hydrated lithium sulfate is made by titration from the soluble base lithium hydroxide.
The sulfuric acid is added slowly from the burette until the indicator just changes colour. The volume of sulfuric acid needed to just neutralise the lithium hydroxide is noted. Describe how you would continue the experiment to obtain pure dry crystals of hydrated lithium sulfate.





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