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?
A)−50. torr
B)50. torr
C)695 torr
D)795 torr
E)None of these choices are correct.

Question

Quizplus · Accepted Answer

The pressure in the flask is equal to the atmospheric pressure plus the pressure difference between the two arms of the manometer. The pressure difference is equal to the height of the mercury column multiplied by the density of mercury and the acceleration due to gravity. Therefore, the pressure in the flask is:$$P_{flask} = P_{atm} + ho g h$$$$P_{flask} = 745 	ext{ torr} + (13.6 g/cm^3)(980 cm/s^2)(5.0 cm)$$$$P_{flask} = 695 	ext{ torr}$$

A Flask Containing Neon Gas Is Connected to an Open-Ended