JEE Chemistry 2026 Question with Solution

Given: A matching question on thermodynamic processes and their magnitudes in $\text{kJ}$.

Find: The correct correspondence between A, B, C, D and I, II, III, IV.

For A: reversible isothermal expansion of $2$ mol ideal gas from $2 \, \text{dm}^3$ to $20 \, \text{dm}^3$ at $300 \, \text{K}$.

Thus, A $\rightarrow$ II.

For B: irreversible isothermal expansion against constant external pressure.

Thus, B $\rightarrow$ I.

For C: change in internal energy.

Thus, C $\rightarrow$ III.

For D: change in enthalpy at constant pressure.

Thus, D $\rightarrow$ IV.

So the final matching is

Therefore, the correct option is B.

Given: Each item in List-I asks for either work, internal energy change, or enthalpy change.

Find: Which magnitude in List-II matches each process.

1. For a reversible isothermal process of an ideal gas, use the logarithmic work expression.
2. For an irreversible expansion against constant external pressure, use $P_{\text{ext}}\Delta V$.
3. For change in internal energy, use $\Delta U = nC_V\Delta T$.
4. For change in enthalpy, use $\Delta H = nC_P\Delta T$.

Applying these:

• A gives $11.5 \, \text{kJ}$, so A $\rightarrow$ II.
• B gives the value marked in the solution as I.
• C gives about $6 \, \text{kJ}$, so C $\rightarrow$ III.
• D gives about $7 \, \text{kJ}$, so D $\rightarrow$ IV.

Hence the correct sequence is A-II, B-I, C-III, D-IV, which corresponds to Option B.