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Concentrated hydrochloric acid when kept in open air, sometimes produces a cloud of white fumes. The explanation for it is that

1. oxygen in air reacts with the emitted HCl gas to form a cloud of chlorine gas
2. strong affinity of HCl gas for moisture in air results in forming of droplets of liquid solution which appears like a cloudy smoke.
3. due to strong affinity for water, concentrated hydrochloric acid pulls moisture of air towards itself. This moisture forms droplets of water and hence the cloud.
4. concentrated hydrochloric acid emits strongly smelling HCl gas all the time.

Correct answer: strong affinity of HCl gas for moisture in air results in forming of droplets of liquid solution which appears like a cloudy smoke.

Solution

Concentrated HCl is volatile; the escaping HCl gas has a strong affinity for water vapour in the air and condenses it into tiny droplets of hydrochloric acid solution, which appear as white fumes. No oxidation to chlorine occurs.

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