Magnesium ribbon reacts with dilute hydrochloric acid. Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) (a) The graph shows the volume of hydrogen gas produced at 20°C as the reaction proceeds. The magnesium is in excess. [Figure 3.1] The experiment is repeated using a lower concentration of hydrochloric acid. The volume of acid used and all other conditions are the same.

1. (a)Draw a line on the grid to show how the volume of hydrogen gas produced changes with time when the reaction is done with a lower concentration of hydrochloric acid.[2]
2. (b)(i)Describe and explain, using ideas about collisions between particles, how the rate of the reaction changes when magnesium powder is used instead of magnesium ribbon. All other conditions are the same.[2]
3. (b)(ii)Describe and explain, using ideas about collisions between particles, how the rate of the reaction changes when the temperature of the reaction mixture is decreased. All other conditions are the same.[2]
4. (c)Calculate the maximum volume, in dm³, of hydrogen formed when 1.68g of magnesium react with excess dilute hydrochloric acid at room temperature and pressure. Give your answer to three significant figures. volume = dm³[2]
5. (d)Magnesium is a good reducing agent. Describe a test for reducing agents. test observations[2]

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