Alcohols (Cambridge (CIE) O Level Chemistry): Exam Questions

Exam code: 5070

4 hours37 questions
1a
1 mark

A student found a recipe for making elderberry wine by fermentation.

  • 1kg elderberries

  • 0.5kg sugar

  • 10g yeast granules

  • 3dm3 water

The student decided to make some elderberry wine using the apparatus below.

fermenting-mixture

The student carried out the following method.

Step 1 The elderberries were crushed.

Step 2 The crushed elderberries and sugar were added to the water and the mixture was boiled for ten minutes. The crushed elderberries were then separated from the mixture.

Step 3 Yeast was added to the liquid when it had cooled to room temperature.

Suggest the purpose of the airlock in the apparatus.

1b
1 mark

What apparatus could be used in Step 1?

1c
2 marks

Draw a labelled diagram of the apparatus used to separate the crushed elderberries from the mixture in Step 2.

1d
1 mark

Why was the yeast in Step 3 not added until the liquid was at room temperature?

1e
3 marks

i)

State one observation during the fermentation.

 

[1]

 

ii)

Suggest how the rate of the fermentation reaction could be measured.

 

[2]

1f
1 mark

Name the method that could be used to separate ethanol from the fermented mixture.

2a
2 marks

A student measures the energy given out when ethanol burns.

A spirit burner filled with ethanol is placed under a metal can containing 200 cm3 of water, with a thermometer in the water.

The burner is lit, left to burn for a few minutes and then put out.

The student works out that 0.60 g of ethanol burned and that the water warmed up by 12.4 °C.

State the readings the student takes to work out these two values.

2b
1 mark

State why the water is held in a metal can and not in a glass beaker.

2c
2 marks

Using data, the student works out that the water should have warmed up by more than 12.4 °C.

Suggest two reasons why the actual rise was smaller.

2d
2 marks

Suggest two ways of changing the apparatus so that the same mass of ethanol warms the water by more.

2e
1 mark

In a second experiment, the water starts at 20 °C and the student expects it to warm up by 90 °C.

Explain why the water cannot warm up by this much.

2f
1 mark

The burner can supply enough energy for a 90 °C rise.

Suggest how a rise of 90 °C could be achieved with the same apparatus and the same volume of water.

3a
1 mark

A student investigates how temperature affects the rate of fermentation.

The student mixes aqueous glucose with yeast in a flask, fits a bung and a delivery tube, and collects the gas given off over a measured time.

The experiment is repeated at 10 °C, 25 °C, 35 °C and 60 °C. The flask is kept at each temperature in a water bath.

State the dependent variable in this investigation.

3b
2 marks

State two variables the student must keep the same in each of the four experiments.

3c
2 marks

At 60 °C, gas was given off for the first few minutes and then stopped completely. At 35 °C, gas was still being given off after the same time.

Explain why the gas stopped being given off.

3d
1 mark

At 10 °C only a very small volume of gas was collected.

Explain why.

3e
2 marks

The student now wants to find the temperature at which the rate of fermentation is greatest.

Describe how the student should change the method.

3f
1 mark

Suggest why the flask is kept at each temperature in a water bath rather than being heated directly with a Bunsen burner.

4
6 marks

A student is asked to compare the energy released when equal masses of ethanol and methanol are burned.

Plan an investigation that the student could carry out.

Your plan should include:

  • the apparatus used

  • the measurements taken

  • how the results are used to compare the two alcohols

  • how the student makes the comparison fair

You may draw a labelled diagram to help answer the question.