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?

Which of the following statements or relationships is not correct in thermodynamic changes?

One mole of an ideal monoatomic gas at temperature $T$ expands adiabatically in an insulated flask from $1 \ L$ to $2 \ L$ against an external pressure of $1 \ atm$. What is the final temperature?

Enthalpy of formation of $HF$ and $HCl$ are $-161 \ kJ$ and $-92 \ kJ$ respectively. Which of the following statements is incorrect?

For an ideal gas, consider only $P-V$ work in going from an initial state $X$ to the final state $Z$. The final state $Z$ can be reached by either of the two paths shown in the figure. Which of the following choice(s) is (are) correct? [take $\Delta S$ as change in entropy and $w$ as work done].
(A) $\Delta S_{X \to Z} = \Delta S_{X \to Y} + \Delta S_{Y \to Z}$
(B) $w_{X \to Z} = w_{X \to Y} + w_{Y \to Z}$
(C) $w_{X \to Y \to Z} = w_{X \to Y} + w_{Y \to Z}$
(D) $\Delta S_{X \to Y \to Z} = \Delta S_{X \to Y}$

One mole of an ideal monoatomic gas is heated in a process $PV^{5/2} = \text{constant}$. The amount of heat absorbed in the process for a $36 \ ^\circ C$ rise in temperature is (in $cal$):