GATE 2026 Chemical Engineering, Q36 · Thermodynamics
The correct answer is C, 1310.
Question
K value is defined as the ratio of mole fraction of a component in the vapor phase to that in the liquid phase. K values at 293 K: at 1100 kPa propane=1.8, iso-butane=0.85; at 1200 kPa propane=1.6, iso-butane=0.75; at 1300 kPa propane=1.4, iso-butane=0.65; at 1400 kPa propane=1.25, iso-butane=0.5; at 1500 kPa propane=1.1, iso-butane=0.45. Which one of the following is closest to the bubble point pressure (in kPa) of an equimolar mixture of propane and iso-butane at 293 K?
Official answer: 1310
Why
GATE 2026 official key: (C). At the bubble point, for the equimolar mixture; interpolating the K-value table, this is satisfied closest to 1310 kPa.
Explanation cross-checked for consistency. Final answer matches the official IIT answer key.