Factors affecting the rate of reaction

Hydrogen peroxide solution, H₂O₂(aq), decomposes to make water and oxygen gas.

Complete the balanced symbol equation for the reaction.

Describe a test and its result which shows that the gas produced in the reaction is oxygen.

Test........

Result........

A hydrogen peroxide solution produces oxygen gas slowly.

A student adds a piece of potato to the hydrogen peroxide solution. The potato contains a biological catalyst.

What name is given to biological catalysts?

Describe and explain the effect of adding the piece of potato to the hydrogen peroxide solution.

Include ideas about rate of reaction and activation energy.

The student measures the total volume of oxygen produced in the reaction with and without the piece of potato.

With the potato, the total volume is: increased, decreased, stays the same.

Tick (✓) one box.

The piece of potato added to the hydrogen peroxide solution is a six-sided cube.

Calculate the surface area of the piece of potato in cm². (i)

A student thinks that cutting the potato into smaller pieces will make the catalyst more effective.

Explain why the student is correct.

Tick (✓) one box.

The student measures the rate of reaction when the piece of potato is added to the hydrogen peroxide.

The rate of reaction is 1.5 cm³ / s.

They then measure the rate of reaction again with an increased concentration of hydrogen peroxide.

What would the rate of reaction be now?

Tick (✓) one box.

Hydrogen peroxide solution, H₂O₂(aq), decomposes to make water and oxygen gas.

Complete the balanced symbol equation for the reaction.

Describe a test and its result which shows that the gas produced in the reaction is oxygen.

Test........

Result........

A hydrogen peroxide solution produces oxygen gas slowly.

A student adds a piece of potato to the hydrogen peroxide solution. The potato contains a biological catalyst.

What name is given to biological catalysts?

Describe and explain the effect of adding the piece of potato to the hydrogen peroxide solution.

Include ideas about rate of reaction and activation energy.

The student measures the total volume of oxygen produced in the reaction with and without the piece of potato.

With the potato, the total volume is: increased, decreased, stays the same.

Tick (✓) one box.

The piece of potato added to the hydrogen peroxide solution is a six-sided cube.

Calculate the surface area of the piece of potato in cm². (i)

A student thinks that cutting the potato into smaller pieces will make the catalyst more effective.

Explain why the student is correct.

Tick (✓) one box.

The student measures the rate of reaction when the piece of potato is added to the hydrogen peroxide.

The rate of reaction is 1.5 cm³ / s.

They then measure the rate of reaction again with an increased concentration of hydrogen peroxide.

What would the rate of reaction be now?

Tick (✓) one box.

15* A student investigates the rate of reaction between pieces of marble chips and an excess of dilute hydrochloric acid.

The diagram shows the equipment they use.

The student measures the total volume of carbon dioxide gas produced every minute until the reaction finishes.

They do two different experiments and plot a graph of the results.

Which experiment has the greater rate of reaction?

Explain your answer by including:

• information from the graph

• a description of how the experiments might be different

• ideas about the reacting particle model including particles and their collisions.

16* A student investigates the rate of reaction between magnesium and an excess of dilute hydrochloric acid.

Strip of magnesium
Dilute hydrochloric acid

The student does three experiments. In the experiments they use the same length of magnesium but change one other variable.

The table shows the results of the three experiments.

Describe the method the student used to get these results, including the variable they may have changed and the variables they controlled.

The student has difficulty filling the measuring cylinder with water.

They change the measuring cylinder for a different piece of apparatus which allows them to measure the volume of hydrogen more accurately.

Name the piece of apparatus they use and complete the diagram below to show this apparatus.

Name of piece of apparatus........

Complete the balanced symbol equation for the reaction.

The student repeats the experiment. The only difference is they use a higher concentration of acid.

Draw a line on the graph to show the results of this experiment.

If the experiment is repeated at a higher temperature, the rate of reaction increases.

Explain why. Use ideas about particles and collisions.

A student investigates the rate of reaction between large pieces of calcium carbonate and dilute hydrochloric acid.

Fig. 13.1 shows two different experiments the student could use. In both experiments the mass decreases as the reaction progresses.

Fig. 13.1

The equation shows the reaction between calcium carbonate and hydrochloric acid.

Use this equation to explain why the mass decreases as the reaction progresses.

The student decides to use Experiment 2 because they think it will produce more accurate results than Experiment 1.

Explain why the student is correct.

The student repeats Experiment 2 with smaller pieces of calcium carbonate to see how this changes the rate of the reaction.

Describe two variables the student must keep the same in this experiment.

Describe and explain the effect of using smaller pieces of calcium carbonate on the rate of the reaction.

The rate of reaction of marble chips with dilute hydrochloric acid depends on the surface area of the marble chips.

Which surface area of the marble chips gives the highest rate of reaction?

0.673 mm² A

1030 mm² B

2.18 × 10³ mm² C

4.98 × 10⁻² mm² D

A student investigates the rate of a reaction at different concentrations.

Fig. 12.1 shows the apparatus he uses.

The student adds dilute hydrochloric acid to the sodium thiosulfate solution. He times how long it takes for the cross to disappear. This is the reaction time.

The student repeats the experiment at different concentrations of sodium thiosulfate solution.

The concentration of hydrochloric acid is the same in each experiment.

He plots the results of the experiment on a graph, as shown in Fig. 12.2.

Look at the equation for the reaction.

Na₂S₂O₃(aq) + 2HCl (aq) → 2NaCl (aq) + H₂O(l) + S(s) + SO₂(g)

Which product in the reaction makes the cross disappear?

Tick (✓) one box.

The rate of reaction can be calculated using the equation:

Use the graph in Fig. 12.2 to calculate the rate of reaction when the concentration of sodium thiosulfate solution is 0.25 mol / dm³.

Give your answer to 2 decimal places.

Rate of reaction =........ / s

Describe the trend shown by the graph in Fig. 12.2.

State how the rate of reaction changes as the sodium thiosulfate concentration changes.

Another student investigates the effect of temperature on the rate of reaction.

She calculates the rate of reaction at different temperatures, as shown in the table.

Predict the rate of reaction at 70 °C.

Predicted rate of reaction =........ / s

A student investigates the rate of reaction between marble chips and hydrochloric acid.

He measures the total mass of carbon dioxide given off for different sizes of marble chips.

Look at a graph of his results.

Which reaction is faster?

Explain how you can tell using data from the graph.

Explain why changing the size of the marble chips changes the rate of the reaction.