Question

Figure shows a cylinder closed by a movable piston containing an ideal gas. The piston is quickly pushed down from position 2. The piston is held at position 2 until the gas is again at `0^(@)C` and then is slowly raised back to position 1. Represent the whole operation on a P-V diagram. If 100 g of ice melts during the cycle, how much work is done on the gas?

Answer 1

A quick process is genernally adiabatic and a show process isothermal. Since 100 g ice melts, heat given out by the systme (gas in the cylinder) is equal to the required laten heat.
`:. Delta Q = - 100 xx 10^(-3) xx 336 xx 10^(3)`
`= - 3360 J`
`Delta U = 0` (since it is a cyclic process)
But `Delta Q = Delta U + Delta W` (always)
`:. - 3360 = Delta W`
`:.` Work done on the system `= - Delta W = 3360 J`