What is calorimetry?

For the reversible isothermal expansion of $1 \, \text{mol}$ of an ideal gas at $300 \, K$ from a volume of $10 \, dm^3$ to $20 \, dm^3$,the value of $\Delta H$ in $kJ$ is:

If $5 \ L$ of an ideal gas at a constant external pressure of $2 \ atm$ expands isothermally to a final volume of '$X$' $L$,the system does a work of $-2,026.4 \ J$. '$X$' (in $L$) is $(1 \ L \cdot atm = 101.32 \ J)$

Which of the following processes involves zero work done?

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

Enthalpy $(H)$ is equal to