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Date November 2012 Marks available 1 Reference code 12N.3.sl.TZ0.E1
Level SL Paper 3 Time zone TZ0
Command term State Question number E1 Adapted from N/A

Question

Acid deposition is a major environmental concern. Although it is usually associated with human activities, natural sources can also contribute to this phenomenon.

State one natural origin of acid deposition.

[1]
a.

State equations which represent chemical transformations of elemental sulfur into sulfurous acid, H2SO3.

[2]
b.

Discuss the possible ways of decreasing acid deposition and its adverse effects on the environment.

[4]
c.

Markscheme

volcano eruption/activity / lightning / microbial activity;

a.

\({\text{S}} + {{\text{O}}_{\text{2}}} \to {\text{S}}{{\text{O}}_{\text{2}}}\);

\({\text{S}}{{\text{O}}_2} + {{\text{H}}_2}{\text{O}} \to {{\text{H}}_2}{\text{S}}{{\text{O}}_3}\);

b.

washing of coal/natural gas / fluidized bed combustion / remove sulfur before/during the burning;

scrubbing exhaust gases;

using catalytic converters;

low-S diesel / fuel switching / use of alternative energy sources/wind/solar/tidal energy;

reduction in energy consumption;

Accept specific examples of energy saving (e.g. use of bicycles instead of cars).

use lime/formula of a reasonable base on rivers/lakes/soils to neutralize the acid;

Allow other methods/solutions.

Award [2 max] for adverse effects of acid deposition on environment.

c.

Examiners report

This was generally answered well although in (a) some thought the natural acidity of rain, caused by dissolved CO2, was what was required.

a.

Part (b) was answered well (although the number of candidates who wrote elemental sulfur as a diatomic molecule was worrying).

b.

There were some good discussions in (c). Many candidates mis-interpreted the question as asking about the effects of acid rain – credit was given.

c.

Syllabus sections

Core » Topic 8: Acids and bases » 8.5 Acid deposition
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