JEE Main 2026 Jan 21 Shift 1, Physics Q24: Laws of Thermodynamics

JEE Main2026Jan 21, Shift 1Physics

10 mole of oxygen is heated at constant volume from 30°C to 40°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 °C and R = 2 cal./mol °C.)

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Solution

At constant volume, $Δ U = n C_{v} Δ T$ . By Mayer's relation, $C_{v} = C_{p} - R = 7 - 2 = 5$ cal/mol·°C.

$Δ U = 10 \times 5 \times (40 - 30) = 500$ cal.

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JEE Main 2026 Jan 21 Shift 1, Physics Q24: Laws of Thermodynamics

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