Propanone, CH3COCH3, reacts with iodine, I2, to form colourless products. CH3COCH3 + I2 → CH3COCH2I + HI The reaction is catalysed by hydrochloric acid. The table shows how the relative rate of this reaction changes when different concentrations of propanone, iodine and hydrochloric acid are used. experiment | concentration of CH3COCH3 in mol/dm³ | concentration of I2 in mol/dm³ | concentration of hydrochloric acid in mol/dm³ | relative rate of reaction ---|---|---|---|--- 1 | 0.025 | 0.024 | 0.12 | 5.1 2 | 0.050 | 0.024 | 0.12 | 10.2 3 | 0.050 | 0.024 | 0.06 | 5.1 4 | 0.050 | 0.012 | 0.06 | 5.1

1. (a)Describe how increasing the concentration of each of these substances affects the relative rate of reaction. propanone iodine hydrochloric acid[3]
2. (b)Increasing the temperature increases the rate of this reaction. Explain why, in terms of kinetic particle theory.[2]
3. (c)Iodine has several isotopes. What are isotopes?[1]
4. (d)Astatine, At, is a halogen. Aqueous iodine reacts with aqueous astatide ions, At–, to produce astatine. Construct the ionic equation for this reaction.[1]
5. (e)Aqueous hydrogen iodide reduces hydrogen peroxide to water. H2O2(aq) + 2H+(aq) + 2I–(aq) → 2H2O(l) + I2(aq) Explain how iodide ions act as a reducing agent in this reaction.[1]