Question

A gas is contained in a metallic cylinder fitted with a piston.the piston is suddenly moved in to compress the gas and is maintained at this position. As time passes the pressure of the gas in the cylinder

Answer 1

The pressure of the gas in the cylinder decreases.

Answer 2

Sudden compression of the gas causes its temperature to rise significantly (approximately an adiabatic process). The metallic cylinder facilitates heat transfer from the hot gas to the cooler surroundings. Since the piston is held fixed, the volume of the gas is constant. According to the ideal gas law ($PV = nRT$), with constant volume ($V$), constant number of moles ($n$), and constant gas constant ($R$), the pressure ($P$) is directly proportional to the temperature ($T$). As heat is lost from the gas to the surroundings, the temperature of the gas decreases. Consequently, the pressure of the gas decreases over time.