GCEChemistryIndustrial and Environmental Chemistry2022

In the contact process for the manufacture of tetraoxosulphate(VI) acid, sulphur(IV) oxide is oxidized to sulphur(VI) oxide using a vanadium(V) oxide catalyst. Which of the following best explains why sulphur(VI) oxide is not dissolved directly in water to form the acid on an industrial scale?

ASulphur(VI) oxide does not react with water under normal conditions
BThe reaction of sulphur(VI) oxide with water produces a corrosive acid mist that is difficult to handle and absorb efficientlyCORRECT
CDissolving sulphur(VI) oxide directly in water causes an explosion
DWater decomposes sulphur(VI) oxide back to sulphur(IV) oxide and oxygen
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Why the answer is B, and why the others tempt you.
When SO₃ is added directly to water, it reacts so vigorously that it forms a fine acid mist (fog) of H₂SO₄ droplets which is extremely difficult to contain and absorb, creating both safety hazards and industrial inefficiency. Instead, SO₃ is first dissolved in concentrated H₂SO₄ to form oleum (H₂S₂O₇), which is then carefully diluted with water to produce concentrated H₂SO₄. Options A and D are chemically incorrect, and option C overstates the hazard inaccurately.
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