A cylinder contains a dilute gas at pressure P i and volume V i . One end wall of the cylinder is movable (forming a piston); moving this wall changes the volume of the gas. Suppose the gas is compressed so that the final pressure is twice the initial pressure, P f = 2 P i . If the temperature is constant (so that Boyle\'s law applies), what is the final density? a.The final density is equal to the initial density. b.The final density is twice the initial density. b.The final density is half the initial density. Solution Use Boyle’s law: Pi*Vi = Pf*Vf Vf/Vi = Pi/Pf = 1/2 So, volume decreases by half use: density = mass / volume since mass of gas inside cylinder is not changing, decreasing volume by half will increase the density to 2 times Answer: b .