In a reversible isothermal process,the change in internal energy is

Internal energy does not include

Two moles of an ideal gas are expanded isothermally from $15 \ dm^3$ to $20 \ dm^3$. If the amount of work done is $-6 \ dm^3 \ bar$,find the external pressure needed to obtain this work.

What is the enthalpy change (in $J$) for converting $9 \ g$ of $H_2O(l)$ at $+10^{\circ}C$ to $H_2O(l)$ at $+20^{\circ}C$? $(C_p(H_2O(l)) = 75 \ J \ mol^{-1} \ K^{-1})$

For the isothermal expansion of an ideal gas:

$2 \ \text{moles}$ of a gas undergoes a change in state from $(2 \ \text{bar}, 40 \ \text{L})$ to $(5 \ \text{bar}, 15 \ \text{L})$ at a constant temperature. If the change in internal energy is given by $35 \ \text{bar-L}$, then the enthalpy change for the process will be: (in $\text{bar-L}$)