One mole of diatomic ideal gas undergoes a cyclic process ABC as shown in the figure. The process BC is adiabatic. The temperatures at A, B and C are 400 K, 800 K and 600 K, respectively. The correct statement is (a) The change in internal energy in whole cyclic process is 250R (b) The change in internal energy in the process CA is 700R (c) The change in internal energy in the process AB is -350R (d) The change in internal energy in the process BC is -500R

Answer: (d). Diatomic gas: Δ U = nCVΔ T with CV = 5/2R, n = 1. BC: Δ U = 5/2R(600 - 800) = -500R. Check others: whole cycle Δ U = 0; CA: 5/2R(-200) = -500R; AB: 5/2R(400) = +1000R. So the answer is (d).

One mole of diatomic ideal gas undergoes a cyclic process ABC as… | MHT CET 2026 (19 May, Shift 2)

Q17MHT CET 2026 · 19 MAY · SHIFT 2Difficult

P-V Diagrams & Cyclic Processes

One mole of diatomic ideal gas undergoes a cyclic process ABC as shown in the figure. The process BC is adiabatic. The temperatures at A, B and C are $400$ K, $800$ K and $600$ K, respectively. The correct statement is

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Answer: (d)

Diatomic gas: $\Delta U = nC_V\Delta T$ with $C_V = \frac{5}{2}R$ , $n = 1$ .
BC: $\Delta U = \frac{5}{2}R(600 - 800) = -500R$ .
Check others: whole cycle $\Delta U = 0$ ; CA: $\frac{5}{2}R(-200) = -500R$ ; AB: $\frac{5}{2}R(400) = +1000R$ .
So the answer is (d).

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P-V Diagrams & Cyclic Processes question from MHT CET 2026 (19 May, Shift 2)

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