Determine the purity of sulphuric acid made by dissolving 7.0 g of impure acid in distilled water to make 1 dm3 of solution (labelled K) by reacting it with solution L made by dissolving 4.0 g of sodium hydroxide in distilled water to make 1 dm3 . Carry out the titration using either phenolphthalein (POP) or methyl orange (MO) indicator, obtain three titre volumes and tabulate the results.

1. Why both phenolphthalein (POP) and methyl orange (MO) indicators are suitable for the titration? (4 mk)
2. Why both phenolphthalein (POP) and methyl orange (MO) indicators are suitable for the titration? (0 mk)
3. How much volume of the acid was required for complete neutralization with 20 cm3 or 25 cm3 of the base? (0 mk)
4. How much volume of the acid was required for complete neutralization with 20 cm3 or 25 cm3 of the base? (2 mk)
5. Write a balanced chemical equation for the reaction. (2 mk)
6. Write a balanced chemical equation for the reaction. (0 mk)
7. Calculate the molarity of the acid and the base. (10 mk)
8. Calculate the molarity of the acid and the base. (0 mk)
9. Calculate the percentage purity of the acid. (0 mk)
10. Calculate the percentage purity of the acid. (7 mk)

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Study the reaction between sodium thiosulphate and hydrochloric acid. The chemicals provided are labelled as N1 , N2 , and N3 for 0.13 M sodium thiosulphate, 2.0 M hydrochloric acid and distilled water respectively. You are also provided with a piece of white paper marked X on which a 100 cm3 beaker containing the reaction mixture. Mix volumes of N1 , N2 , and N3 and at the same time record the time taken for the reaction as shown in the following table.

1. Complete filling the table. (0 mk)
2. (i) plot a graph of volume N1 (vertical axis) against time (horizontal axis) taken for the letter X to disappear completely. (ii) comment on the shape of the graph. (0 mk)
3. Explain why did the letter X disappear. (0 mk)
4. Write the electronic configuration of the product which causes the solution to be cloudy (milky). (0 mk)
5. Explain the trend observed in the graph. (5 mk)
6. Write the ionic equation for the reaction between N1 and N2. (0 mk)
7. Explain why N3 was added to N1. (0 mk)

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