Which of the following is not a state function of a thermodynamic system?

The enthalpies of all elements in their standard states are:

$1 \ mol$ of an ideal gas is allowed to expand isothermally and reversibly from $1 \ L$ to $5 \ L$ at $300 \ K$. The change in enthalpy (in $kJ$) is $(R = 8.3 \ J \ K^{-1} \ mol^{-1})$.

When $50 \ g$ of iron is dissolved in $HCl$ at $25 \ ^\circ C$ in a closed vessel,the work done is calculated to be ..... . The atmospheric pressure is $1 \ atm$. (in $J$)

For an ideal gas,the heat of reaction at constant pressure and constant volume are related as:

Work done when $2 \ mol$ of an ideal gas is compressed from a volume of $5 \ m^{3}$ to $2.5 \ m^{3}$ at $300 \ K$, under a constant external pressure of $100 \ kPa$ is: (in $kJ$)