Explain why water cannot be used in place of mercury in a barometer?
The atmospheric pressure at sea level = 76cm of Hg = 1.013x105 Pascal.
If we fill the water in barometer tube, the height of water column required to balance the atmospheric pressure will be,
That is, if water is used in barometer tube instead of mercury, the length of the tube must be greater than 10.326 cm. A greater height will be difficult to hold in a vertical position and needs a high tower to install the barometer.
So, we cannot replace mercury by water in the barometer.