A flask containing neon gas is connected to an open-ended mercury manometer. The open end is exposed to the atmosphere, where the prevailing pressure is 745 torr. The mercury level in the open arm is 50. mm below that in the arm connected to the flask of neon. What is the neon pressure, in torr?

Gas pressure = 695 torr

Explanation:

If the mercury level to an open-ended of manometer is higher than the mercury level of the arm connected to the gas flask, then atmospheric pressure is lower than gas pressure.

Gas pressure = Atmospheric pressure + Δh

where Δh is the difference in mercury level of both arm.

And if the mercury level to an open-ended of manometer is lower than the mercury level of the arm connected to the gas flask, then atmospheric pressure is greater than gas pressure.

Gas pressure = Atmospheric pressure - Δh

Given dа ta:

Atmospheric pressure = 745 torr = 745 mmHg (Because 1 torr = 1 mmHg)

Δh = 50 mm

As in our case, mercury level to an open-ended of manometer is lower than the mercury level of the arm connected to the neon gas flask. So,

Gas pressure = Atmospheric pressure - Δh

Gas pressure = 745 - 50

Gas pressure = 695 mm Hg

Gas pressure = 695 torr