Q84 / 90 · JEE Main 2022 (29 Jul Shift 1) · Physics

One mole of a monoatomic gas is mixed with three moles of a diatomic gas. The molecular specific heat of mixture at constant volume is α24R J mol K-1; then the value of α will be _____ . (Assume that the given diatomic gas has no vibrational mode.)

Correct answer: 3

Solution

Molecular specific heat at constant volume in terms of degrees of freedom is given by CV=f2R

Molecular specific heat of mixture at constant volume is CV/mix=n1CV1+n2CV2n1+n2

=1×3R2+3×5R21+3

=9R4=α24R

⇒α=3

Hence, the correct answer is 3.

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