Name the process which is associated with dissipated energy process and reduce the efficiency.

For the free expansion of a gas,which of the following is true?

In case of free expansion, which one of the following statements is $\underline{\text{WRONG}}$?

Is the rusting of iron a reversible process? Why?

Which process is acceptable in nature: a reversible or an irreversible process?

$A$ container with insulating walls is divided into two equal parts by a partition fitted with a valve. One part is filled with an ideal gas at a pressure $P$ and temperature $T$,whereas the other part is completely evacuated. If the valve is suddenly opened,the pressure and temperature of the gas will be