Water & Water Pollution (CIE IGCSE Chemistry: Co-ordinated Sciences (Double Award))

This question is about water.

Describe a chemical test which shows the presence of water.

test ..................................................

colour change if water is present  ..................................................

How could you show that a sample of water is pure?

Describe how water is treated before it is supplied to homes and industry.

Water is needed for industry and in the home.

In many regions, drinking water is obtained by the distillation of sea-water. Explain how distillation separates the water from sea-water.

The diagram below shows part of the Water Cycle.

The rain drains into rivers and then into reservoirs. Describe how water is treated before it enters the water supply.

Calcium nitrate is used as a fertiliser to help prevent blossom end rot in tomatoes which causes browning of the bottom of the fruit. It provides both calcium and nitrogen.

Write the formula for calcium nitrate.

Waste water like this needs to be treated before being released into the environment. Waste water may require removal of organic matter and harmful chemicals. The three main steps are sedimentation, filtration and chlorination.

Explain what happens in sedimntation.

Explain why chlorination is required.

Table 5.1 shows some information about how the treated solid sludge was disposed of from one sewage treatment plant in 2000 and 2020.

Table 5.1

Calculate the percentage of treated solid sludge that was sent to landfill in 2000.

Give your answer to 3 significant figures.

The total mass of treated solid sludge increased from 2000 to 2020 and the proportions of how the sludge was disposed of changed.

Suggest one reason for the increase in the total mass of treated solid sludge and two reasons for the changes in the proportions of the disposal methods.

Use Table 5.1 to help you answer.

Fertilisers are used to promote plant growth.

Two fertilisers are ammonium phosphate, (NH₄)₃PO₄, and calcium dihydrogenphosphate,Ca(H₂PO₄)₂.

Describe a test to distinguish between these two fertilisers.

test ..................................................

result ..................................................

Higher tier only

The equation for the decomposition of copper(II) nitrate is given below.

2Cu(NO₃)₂ → 2CuO + 4NO₂ + O₂

Copper(II) nitrate forms a series of hydrates with the formula Cu(NO₃)₂.xH₂O.

All these hydrates decompose to form copper(II) oxide.

1 mole of Cu(NO₃)₂.xH₂O forms 1 mole of CuO.
 

Groundwater can contain fertilisers washed from fields. An example of a fertiliser that can be found is ammonium nitrate. 

Water from reservoirs is treated to make it suitable for drinking. Even though the water has been treated it is not pure. One method to purify water is de-ionisation.

Describe another method which will produce pure water.

Chlorine is added to drinking water in order to make it safe to drink. The chlorine kills miro-organisms that can cause illnesses such as cholera and typhoid.

Suggest a concern with adding chlorine to drinking water.

A scientist finds an unlabelled bottle on a shelf.

She thinks the bottle contains a solution of ammonium sulfate, (NH₄)₂SO₄.

Describe tests the scientist could do to show that the solution is ammonium sulfate.

Ammonium sulfate is often used as a fertiliser.

It is prepared by reacting ammonia (NH₃) with sulfuric acid (H₂SO₄).