The incorrect expression among the following is:

An ideal gas is expanded from $(p_1, V_1, T_1)$ to $(p_2, V_2, T_2)$ under different conditions. The correct statement$(s)$ among the following is(are):
[$A$] The work done on the gas is maximum when it is compressed irreversibly from $(p_2, V_2)$ to $(p_1, V_1)$ against constant pressure $p_1$.
[$B$] The work done by the gas is less when it is expanded reversibly from $V_1$ to $V_2$ under adiabatic conditions as compared to that when expanded reversibly from $V_1$ to $V_2$ under isothermal conditions.
[$C$] The change in internal energy of the gas is $(i)$ zero,if it is expanded reversibly with $T_1=T_2$,and $(ii)$ positive,if it is expanded reversibly under adiabatic conditions with $T_1 \neq T_2$.
[$D$] If the expansion is carried out freely,it is simultaneously both isothermal as well as adiabatic.

The difference between enthalpy change and internal energy change for the combustion of one mole of ethyl alcohol is

Five moles of a gas are subjected to a series of changes as shown in the given graph. What are the processes $A \rightarrow B$,$B \rightarrow C$,and $C \rightarrow A$ respectively?

The enthalpy of combustion of methane at $25\,^{\circ}C$ is $890\,kJ$. The heat liberated when $3.2\,g$ of methane is burnt in air is.....$kJ$

Which of the following is (are) an endothermic reaction?