JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Heat & Thermodynamics

Heat is supplied to a diatomic gas at constant pressure. Then the ratio of

Δ Q : Δ U : Δ W

is ____.

(A) $2 : 3 : 5$
(B) $5 : 3 : 2$
(C) $2 : 5 : 7$
(D) $7 : 5 : 2$ ✓ Correct

Answer: (D)

Solution

For a diatomic gas heated at constant pressure,

Δ Q = n C_{P} Δ T = \frac{7}{2} n R Δ T

, the internal-energy change is

Δ U = n C_{V} Δ T = \frac{5}{2} n R Δ T

, and the work done is

Δ W = P Δ V = n R Δ T

. Hence

Δ Q : Δ U : Δ W = \frac{7}{2} : \frac{5}{2} : 1 = 7 : 5 : 2

. The ratio

Δ Q : Δ U : Δ W

7 : 5 : 2

JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Single correct option

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