Which of the following processes involves zero work done?

Choose the reaction in which $\Delta H$ is not equal to $\Delta U$.

Explain free expansion.

In thermodynamics,a process is reversible when:

$A$ sample of $1.0 \ mol$ of a monoatomic ideal gas is taken through a cyclic process of expansion and compression as shown in the figure. What will be the value of $\Delta H$ for the cycle as a whole?

$A$ given mass of gas expands from state $A$ to state $B$ by three paths $1, 2$ and $3$ as shown in the figure. If $w_1, w_2$ and $w_3$ are the work done by the gas along the three paths respectively,then: