An exothermic reaction is one in which the reacting substances

For a massless piston undergoing an expansion of $\Delta V$ at constant temperature against a variable external pressure $P$,which equation represents the work done?

The enthalpies of the elements in their standard states are assumed to be

Point out the wrong statement in relation to enthalpy.

For a change in state of $1 \, \text{mole}$ of a non-ideal gas,the change in internal energy is $\Delta U = 30.0 \, \text{L} \cdot \text{atm}$. The state changes from $(2.0 \, \text{atm}, 3.0 \, \text{L}, 95 \, \text{K})$ to $(4.0 \, \text{atm}, 5.0 \, \text{L}, 245 \, \text{K})$. What is the change in enthalpy $(\Delta H)$ in $\text{L} \cdot \text{atm}$?

Which of the following sets represents the normal physical states of the elements concerned at $25\,^{\circ}C$ and $1 \ bar$ pressure,for which $\Delta H^{\circ}_{f} = 0$?