In a manometer the mercury level at the open end of the tube is 215 mm higher than at the closed end of the tube. If the atmospheric pressure is 1 atm, what is the pressure of the gas sample in units of torr?
The pressure difference between the closed end (gas sample) and the open end is
P_gas - P_air = rho * g * ...
The solution calculates the pressure of the gas sample in the manometer.