An ideal-gas mixture at 500 kPa contains 30 mol% component A. Its partial pressure is most nearly:
- (A)150 kPa
- (B)200 kPa
- (C)350 kPa
- (D)500 kPa
Show worked solution
Answer: (A)
Dalton's law gives p_A=y_A P=0.30(500)=150 kPa.
Ideal-mixture partial pressure is proportional to mole fraction.
The component occupies 30% of the total moles.
FE Reference Handbook — Thermodynamics: Ideal-Gas Mixtures
Why the other choices appear
- (B)Using the complement mole fraction and an unrelated half factor gives 200 kPa.
- (C)Using component B's 70% fraction gives its partial pressure.
- (D)Reporting total pressure ignores mixture composition.