You are provided with five gas jars containing SO2, CO2, H2, CO and NO respectively....

JAMB 1978

You are provided with five gas jars containing SO2, CO2, H2, CO and NO respectively. Select a test from A to E which will identify ANY ONE of the gases completely

A. pass each gas into lime water
B. pass each gas into water and test with litmus paper
C. pass each gas into concentrated sulphuric acid
D. expose each gas to atmospheric air
E. expose each gas to fumes of hydrogen chloride

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Correct Answer: Option D

Explanation

Option D is correct because exposing the gas jars to atmospheric air allows Nitrogen(II) oxide (NO) to be definitively identified. (NO) is a colourless gas that immediately reacts with oxygen in the atmospheric air to form Nitrogen(IV) oxide ((NO\(_2\)), which is a highly visible reddish-brown gas.

Option A is incorrect because passing the gases into lime water (Ca(OH)\(_2\)) cannot completely isolate a single gas. While carbon dioxide (CO\(_2\)) turns lime water milky due to the formation of insoluble calcium carbonate (CaCO\(_3\)), sulphur dioxide (SO\(_2\)) also turns lime water milky by forming an insoluble precipitate of calcium sulfite (CaSO\(_3\)). Therefore, it fails to identify just one gas completely.

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