Mercury boils at `367^(@)C`. However, mercury thermometers are made such that they can measure temperature up to `500^(@)C`. This is done by

Options

A. maintaining vacuum above mercury column in the stem of the thermometer
B. filling nitrogen gas at high pressure above the mercury column
C. filling nitrogen gas at low pressure above the mercury level
D. filling oxygen gas at high pressure above the mercury column

Answer

B

Explanation

By filling nitrogen gas at high pressure, the boling point of mercury is increased which extend the range upto `500^(@)C`.