Question

A piston cylinder device initially contains $0.2m^3$ neon (assume ideal) at 200 kPa inside at $T_1^{0}C$. A value is now opened and neon is allowed to escape until the volume reduces to half the initial volume. At the same time heat transfer with outside at $T_2^{0}C$ ensures a constant temperature inside. Select the statement(s) for given process :

• A. $\Delta U$ must be zero
• B. $\Delta U$ may not be zero
• C. q may be +ve
• D. q may not be -ve

Answer 1

Answer: (A)

$\Delta U$ must be zero

The process is Isothermal as temperature constant inside.

for Isothermal $DU=0$ when gas expands work done by the system is

$-ve$ and q is positive.

Option A is correct.