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GATE 2025 Chemical Engineering, Q32 · Thermodynamics

The correct answer is 9.651 to 9.692.

Question

The following data is given for a ternary ABC gas mixture at 12 MPa and 308 K: mole fractions yA=0.55,yB=0.20,yC=0.25;y_{A}=0.55, y_{B}=0.20, y_{C}=0.25; fugacity coefficients φA=0.75,φB=0.80,φC=0.95.φ_{A}=0.75, φ_{B}=0.80, φ_{C}=0.95. The fugacity of the gas mixture is _____ MPa (rounded off to 3 decimal places).

Official answer: 9.651 to 9.692

Why

GATE 2025 official key: 9.651 to 9.692. Mixture fugacity ≈P⋅Σ(yiφi)=12×(0.55×0.75+0.20×0.80+0.25×0.95)≈12×0.81≈9.7\approx P\cdot \Sigma (yᵢφᵢ) = 12 \times (0.55 \times 0.75 + 0.20 \times 0.80 + 0.25 \times 0.95) \approx 12 \times 0.81 \approx 9.7 MPa, within the official range.

Explanation is AI-assisted, under review. Final answer matches the official IIT answer key.

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