1. The problem statement, all variables and given/known data A thin U-tube with cross sectional areas sealed at one end and open to atmosphere at the other end consists of two bends of length l=250 mm each, forming right angles. The vertical parts of the tube are filled with mercury to half the height that is l/2 on both sides of the U-tube. All of the mercury can be displaced from the tube by heating slowly the gas in the sealed end of the tube which is separated from atmospheric air by mercury. The work done by the gas thereby is xPoρl. Find x. Po= Atmospheric pressure=ρHggl/2 ρ=density of gas ρHg= density of mercury. g=acceleration due to gravity. Note : All the bends of the U-tube are of length l=250 mm. 2. Relevant equations Work done by gas = ∫PdV 3. The attempt at a solution Since the question says that mercury filled on both sides of the tube is l/2 we have by pascal's law : Po=Pressure exerted by gas at sealed end on mercury. Now to displace it i use work done by gas as pressure Po times change in volume which would require cross sectional area of tube which is not given in the question. Please help! Thanks in advance... :) Edit : Given : x is an integer and can range from 0 to 9.