1.1. A student investigated the rate of reaction between magnesium ribbon and four different solutions of dilute sulfuric acid, A, B, C and D. The sulfuric acid was in excess in all experiments. Four experiments were carried out.

Experiment 1

Using a measuring cylinder, 30 cm³ of aqueous sulfuric acid A was poured into a beaker.

The stop clock was started and a 4 cm length of magnesium was added to the sulfuric acid in the beaker. The mixture was stirred constantly.

The time taken for all of the magnesium to react and disappear was measured. The beaker was rinsed out with distilled water.

Experiment 2

Experiment 1 was repeated using solution B of sulfuric acid.

Experiments 3 and 4

Experiment 1 was repeated, using solutions C and D of sulfuric acid.

Use the stop clock diagrams to record the times in the table. 

1.2. Plot the results for Experiments 1, 2, 3 and 4 on the grid and draw a smooth line graph.

1.3. i) From your graph, deduce the concentration of the sulfuric acid if the time for the reaction was 80 s. Show clearly on the graph how you worked out your answer.

   .......................... mol/dm³

[2]

ii) From your graph, deduce how long the reaction would take if a solution of sulfuric acid of concentration 1.2 mol/dm³ was used. Show clearly on the graph how you worked out your answer.

.......................... s

[2]

1.4. Why was the same amount of magnesium used in Experiments 1, 2, 3 and 4? 

1.5. Another experiment was carried out.

A 4 cm length of magnesium ribbon was added to dilute sulfuric acid. The temperature of the solution was measured before and after the reaction. The observations were recorded and the gas given off tested.

Observations: Rapid effervescence and the tube felt hot. A lighted splint popped.

Use the thermometer diagrams to record the temperatures.

1.6. What type of chemical reaction occurred when magnesium reacted with sulfuric acid?

.......................................................................................................................................

[1]

ii) Identify the gas given off. .......................................................................................................................................

[1]

iii) Suggest the effect on the temperature change if this experiment was repeated using 2 cm of magnesium ribbon.

[2]