Is it true that in the barometer, (a device which is used to measure the atmospheric pressure), there will be no effect on the measurement when the mercury in it is damp?

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True

False

answer is B.

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Detailed Solution

The given statement is false.
A barometer is used to measure the atmospheric pressure in terms of the height of the mercury column. Because of its high density, mercury is commonly used in barometers. Under normal atmospheric pressure, the mercury column takes a height of

76 cm

.
If the mercury in it is damp, then a small amount of water will evaporate into the vacuum. Then the formed water vapour would exert pressure on the mercury, which causes its level to fail. Hence the moisture present in mercury will increase its density and vapour pressure, and therefore the barometric height increases.
The correct statement would be that in the barometer (a device used to measure the atmospheric pressure), if the mercury in it is damp, then a small amount of water will evaporate into the vacuum.

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