Chemistry 5070 · O Level · Rate of reaction

Rate of reaction — practice question

Magnesium ribbon is made to react with dilute hydrochloric acid. $\text{Mg(s)} + 2\text{HCl(aq)} \rightarrow \text{MgCl}_2\text{(aq)} + \text{H}_2\text{(g)}$ The graph indicates the volume of hydrogen gas obtained at $20\degree\text{C}$ as the reaction continues. Magnesium is in excess. The experiment is carried out again with a lower concentration of hydrochloric acid. The volume of acid used and every other condition stay the same.
(a)[2]

Draw a line on the grid showing how the volume of hydrogen gas changes with time when the reaction is done using a lower concentration of hydrochloric acid.

(b(i))[2]

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. Every other condition remains unchanged.

(b(ii))[2]

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. Every other condition remains unchanged.

(c)[2]

Calculate the largest volume, in $\text{dm}^3$, of hydrogen produced when $1.68\,\text{g}$ of magnesium react with excess dilute hydrochloric acid at room temperature and pressure. Give your answer to three significant figures.

(d)[2]

Magnesium acts as a good reducing agent. Describe a test for reducing agents. test observations

Worked solution & mark scheme

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