\(2SO_2 (g) + O_2 (g) \overset{V_2O_5}{\longrightarrow} 2SO_3 (g)\, \ \Delta H = -196.6\text{kJ mol}^{-1} \)
For the above given reaction, identify the incorrect statement from the following
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → The forward reaction leads to an increase in volume
In the contact process, sulphur dioxide is oxidised to sulphur trioxide over \( \ce{V2O5} \). Three moles of gas (2 + 1) give two moles of gas.
Option (1) It is an exothermic reaction — A correct statement about this reaction. ΔH is negative.
Option (2) It is a reversible reaction — A correct statement about this reaction. It is an equilibrium.
Option (3) The forward reaction leads to an increase in volume — The incorrect statement. 3 mol of gas give 2 mol, so the volume decreases.
Option (4) The forward reaction leads to a decrease in volume — A correct statement about this reaction. 3 mol of gas give 2 mol.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Sulphuric Acid – …
