GCSE AQA Chemistry Rate of Reaction: Some students investigated the r

Question

Some students investigated the rate of decomposition of hydrogen peroxide, H2O2.
The equation for the reaction is:

2H2O2(aq) → 2H2O(l) + O2(g)

The catalyst for the reaction is manganese dioxide.

1. Describe a test to identify the gas produced in the reaction.

Give the result of the test.

Student A investigated the effect of the particle size of manganese dioxide on the rate of the reaction.
This is the method used.

1. Measure 25 cm³ of 0.3 mol/dm³ hydrogen peroxide solution into a conical flask.
2. Add a spatula of fine manganese dioxide powder to the conical flask.
3. Measure the volume of gas produced every minute for 10 minutes.
4. Repeat steps 1 to 3 with some coarse manganese dioxide lumps.

The method student A used did not give valid results.

What two improvements could student A make to the method to give valid results?

Tick (✓) two boxes.

Measure the increase in mass of the conical flask and contents.
Measure the volume of gas produced every 2 minutes.
Place the conical flask in a water bath at constant temperature.
Use 0.05 mol/dm³ hydrogen peroxide solution.
Use a mass of 1 g manganese dioxide each time.

Student B used a method which gave valid results.

Figure 9 shows student B's results.

Determine the mean rate of reaction in cm³/s between 2 and 4 minutes for coarse manganese dioxide lumps.

Give your answer to two significant figures.

Use data from Figure 9.

Mean rate of reaction = _____________ cm³/s

Hydrogen peroxide molecules must collide with manganese dioxide particles for catalysis to take place.

Student B repeated the experiment with coarse lumps of manganese dioxide.

Student B used the same volume of 0.2 mol/dm³ hydrogen peroxide instead of 0.3 mol/dm³ hydrogen peroxide.

Sketch on Figure 9 the curve you would expect to see.

Assume that the reaction is complete after 9 minutes.

The rate of reaction is different when manganese dioxide is used as a fine powder rather than coarse lumps.

Explain why.

You should answer in terms of collision theory.

Some students investigated the rate of decomposition of hydrogen peroxide, H2O2 - AQA - GCSE Chemistry - Question 9 - 2019 - Paper 2

Worked Solution & Example Answer:Some students investigated the rate of decomposition of hydrogen peroxide, H2O2 - AQA - GCSE Chemistry - Question 9 - 2019 - Paper 2

Describe a test to identify the gas produced in the reaction.

What two improvements could student A make to the method to give valid results?

Determine the mean rate of reaction in cm³/s between 2 and 4 minutes for coarse manganese dioxide lumps.

Sketch on Figure 9 the curve you would expect to see.

Explain why the rate of reaction is different when manganese dioxide is used as a fine powder rather than coarse lumps.

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