ALS14A(ENVIROMENT) - Section 14.1 Chemistry and the...

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Section 14.1/ Chemistry and the environment / SKH Bishop Baker Secondary School AL Chemistry Section 14 Chemistry and Society (14.1 Chemistry and the environment) AS95B Q.11 (b) (i) The waste water should be neutralized / treated with a base to bring its pH back to 6.0 - 9.0 before it is discharged . [1] (ii) DO less than 4.0 mg dm -3 may cause death of aquatic life / [ ½ ] fish due to low DO [ ½ ] odour problem / emission of toxic gas resulted from the [ ½ ] anaerobic degradation of organic matters . [ ½ ] (iii) The amount of oxygen required to breakdown the organic matters in water. [1] Animal wastes contain a lot of organic matter which upon [ ½ ] degradation will consume the DO . [ ½ ] (iv) Pass the sewage through a screen (filter) which traps / removes large solids . [1] Add (aerobic) bacteria to break down carbohydrates and protein (organic matters ) into simpler substances . [1] Add chlorine (or by other means) to kill the bacteria . [1] AS95B Q.13 (b) ( I ) (iv) Incineration of PVC produces HCl which [ ½ ] causes acid rain / damages human respiratory system . [ ½ ] The acidic gas can be removed by wet scrubbing [ ½ ] i.e. to wash the exhaust gas with an alkaline solution before [ ½ ] releasing it to the atmosphere. / Wash with water . (II) (v) Nickel(II) ions can be removed by precipitation with NaOH/Na 2 CO 3 . (or by passing the waste solution through a cation /ion exchange resin .) [1] AS96A Q.6 (a) Air pollutant Process Measure nitrogen dioxide combination between N 2 and O 2 at high temperature [ ½ ] e.g., in car engines, incinerators [ ½ ] installation of catalytic converter/low nitrogen oxides burner [1] [1] + [1] carbon monoxide incomplete combustion [ ½ ] of fossil fuels e.g., petrol, coal [ ½ ] installation of catalytic converter/increase the supply of air [1] [1] + [1] (b) (i) SO 2 causes damage to respiratory system /increase in asthma attacks . [1] (ii) Use of low sulphur fuel / installation of scrubbers . [1] (c) Ozone / suspended particulates (RSP / TSP) / carbon particles . [1] (Also accept hydrocarbons/lead compounds) (d) Minimize exposure / reduce physical activities / mouth cover. [1] AS96A Q.7 ( I ) (c) Accept the following answers : eutrophication + nitrate contamination [1 + 1] or eutrophication + how it arises (1 + 1) or high nitrate levels in drinking water are harmful to human body, particularly to babies . (1 + 1) 1
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Section 14.1/ Chemistry and the environment / or bacteria in intestine may convert nitrate(V) to nitrate(III) which interferes with the oxygen carrying capacity of blood cell (asphyxia) (1 + 1) AS96B Q.11 (a) (i) Ozone can absorb/remove (by photolysis)/filter out the harmful ultraviolet radiation from the sun [1] which can cause skin cancer / reduce crop yield . [1] (ii) Any TWO of the following [1 + 1] As aerosol propellant /blowing agents in plastic industry/ solvents in dry cleaning/refrigerants /in fire extinguishers .
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