Heat is supplied to a diatomic ideal gas at constant pressure. Assuming the usual active translational and rotational degrees of freedom, what is the ratio ΔQ:ΔU:W for the process?
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Question

Heat is supplied to a diatomic ideal gas at constant pressure. Assuming the usual active translational and rotational degrees of freedom, what is the ratio ΔQ:ΔU:W for the process?

G1 Physics · Accepted Answer

For a diatomic ideal gas under ordinary conditions, Cᵥ = 5R ÷ 2, Cₚ = 7R ÷ 2. At constant pressure, ΔQ = nCₚΔT = (7 ÷ 2)nRΔT. The change in internal energy is ΔU = nCᵥΔT = (5 ÷ 2)nRΔT. The work done is W = nRΔT. Therefore, ΔQ:ΔU:W = (7 ÷ 2):(5 ÷ 2):1 = 7:5:2. Correct option: D.