JEE Main · 2026 · 21 Jan 2026 · Shift 1 · Heat & Thermodynamics

10 mole of oxygen is heated at constant volume from

3 0^{\circ} C

4 0^{\circ} C

. The change in the internal energy of the gas is ______ cal. (The molecular specific heat of oxygen at constant pressure,

C_{p} = 7 cal ./ mol^{\circ} C

and

R = 2 cal ./ mol^{\circ} C

Answer: 500

Solution

At constant volume all the heat goes into internal energy,

Δ U = n C_{V} Δ T

. With

C_{V} = C_{p} - R = 7 - 2 = 5 cal mo l^{- 1}^{\circ} C^{- 1}

and

Δ T = 40 - 30 = 10^{\circ} C

Δ U = 10 \times 5 \times 10 = 500 cal

JEE Main · 2026 · 21 Jan 2026 · Shift 1 · Integer answer

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