CIE Nov 2013 v1 Paper 4 Q8

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Examiners For Use 16 In a world with a rapidly increasing population, access to clean drinking water is critical. For many countries, groundwater sources, rather than stored rainwater or river-water, are vital. Groundwater is water that exists in the pore spaces and fractures in rock and sediment beneath the Earth's surface. The World Health Organisation (WHO) provides maximum recommended concentrations for different ions present in drinking water. (a) The geological nature of the soil determines the chemical composition of the groundwater. The table shows some ions which may contaminate groundwater. ion present WHO maximum permitted concentration / mg dm3 Ba2+ ClNO3 Pb2+ Na+ SO4 2 0.30 250.00 50.00 0.01 20.00 500.00 (i) Nitrate, NO3 What is the reason for this? , ions are dif cult to remove from groundwater.(ii) State which ions in the table above are likely to be removed from the water by treatment with powdered limestone, CaCO3, giving reasons for each of your answers.[4] (b) Nitrates and phosphates can enter water courses such as rivers or streams as a result of human activity. Both of these ions are nutrients for algae. (i) What is the origin of these nitrates?UCLES 2013 9701/41/O/N/13<br /> Examiners For Use 17 (ii) Suggest an origin for the phosphates found in water courses.(iii) What effect do nitrates and phosphates have on water courses?[3] (c) Acid rain can have a major impact on natural waters, particularly lakes. In recent years there has been a worldwide effort to reduce the amount of acid rain produced. (i) Write equations to show the production of acid rain from sulfur dioxide, SO2.(ii) The use of fossil fuels is one major source of sulfur dioxide. Name another major industrial source.[2] [Total: 9]UCLES 2013 9701/41/O/N/13 [Turn over<br />

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