The expansion of gas having no opposing force is called as

Which of the following statements is not correct?

$A$ gas is allowed to expand against a constant external pressure of $2.5 \ bar$ from an initial volume of $2.5 \ L$ to a final volume of $4.5 \ L$. What is the amount of work done (in $J$)?

$A$ perfect gas $(0.1 \ mol)$ having $\overline{C}_{v}=1.50 \ R$ (independent of temperature) undergoes the transformation shown in the graph from point $1$ to point $4$. If each step is reversible,the total work done $(w)$ while going from point $1$ to point $4$ is $(-)$ . . . . . . $J$ (nearest integer). [Given: $R=0.082 \ L \ atm \ K^{-1} \ mol^{-1}$,$1 \ L \ atm = 101.3 \ J$]

Which expression is correct for the work done in adiabatic reversible expansion of an ideal gas?

Which of the following compounds is $NOT$ present in its standard state at $25^{\circ} C$ and $1 \text{ atmosphere}$ pressure?