In thermodynamics,a process is called reversible when

An ideal gas undergoes a cyclic transformation starting from the point $A$ and coming back to the same point by tracing the path $A$ $\rightarrow B$ $\rightarrow C$ $\rightarrow D$ $\rightarrow A$ as shown in the three cases above. Choose the correct option regarding $\Delta U$.

What are extensive properties?

Adiabatic free expansion of an ideal gas must be

$A$ gas is allowed to expand against a constant external pressure of $2.5 \ bar$ from an initial volume '$x$' $L$ to a final volume of $4.5 \ L$. If the amount of work done is $5 \ dm^3 \ bar$,what is the value of '$x$' (in $L$)?

Out of boiling point $(I)$,entropy $(II)$,$pH$ $(III)$ and $emf$ of a cell $(IV)$,intensive properties are