Question

Which property of mercury is the main reason for its use in barometers?

• A. High density
• B. Capillary effect is negligible
• C. Very low vapour pressure
• D. Low compressibility

Hint:

\textbf{Mercury’s low vapour pressure} prevents it from vaporizing and disturbing the pressure balance in barometers.

Answer 1

The Correct Option is C

Mercury is preferred in barometers because it has a very low vapour pressure, even at room temperature.
This ensures that the mercury column inside the barometer does not evaporate easily, which would otherwise lead to inaccurate pressure readings.
While high density is also advantageous (as it allows shorter column heights), the main reason is its low vapour pressure which prevents contamination of the vacuum above the mercury column.