Discussion
Hexane and heptane are completely miscible. At 25 °C, the vapor pressures of hexane and heptane are 0.198 atm and 0.06 atm, respectively. The mole fractions of hexane and heptane in the vapor phase for a solution containing 4 M hexane and 6 M heptane, respectively, are:
Answer: A
The vapour mole fractions are 0.688 hexane and 0.312 heptane.
Treat 4 and 6 as the relative amounts, so the liquid mole fractions are 0.4 and 0.6. By Raoult's law the partial pressures are
\[ \begin{aligned} p_{\mathrm{hex}} &= 0.4 \times 0.198 = 0.0792\ \mathrm{atm} \\ p_{\mathrm{hep}} &= 0.6 \times 0.06 = 0.036\ \mathrm{atm} \end{aligned} \]
\[ y_{\mathrm{hex}} = \frac{0.0792}{0.1152} = 0.688 \]
So hexane is 0.688 and heptane 0.312 of the vapour. The vapour is richer in the more volatile hexane than the liquid is. 0.400 and 0.600 are the liquid composition, and 0.312 and 0.688 swaps the two components.
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development