alleryStart learning →Why is mercury preferred over water as the liquid in a barometer?
AIt boils at a much lower temperature
BIt is about 13.6 times denser than water
CIt expands far more when it is heated
DIt reacts with the air above the column
Answer & Solution
Correct answer: B. It is about 13.6 times denser than water
1. Hydrostatic pressure depends on the height of the column and the density of the liquid.
2. A denser liquid supports the same pressure with a shorter column.
3. Mercury is about 13.6 times denser than water, so a mercury barometer needs only about one thirteen point six of the height.
4. A water barometer would need to stand more than 10 metres tall, which is unworkable in a laboratory.
5. A liquid that reacts with air or boils easily would be useless in a barometer, so those options describe faults rather than reasons.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 9 "Gases", section 9.1 Gas Pressure_
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