Final answer:
The mole fraction of heptane vapor over a solution of heptane and octane can be determined using Raoult's law, which involves the vapor pressures of the pure substances and the molar amounts of each compound in the solution.
Step-by-step explanation:
Calculating the Mole Fraction of Heptane Vapor
The question aims to determine the mole fraction of heptane vapor above a solution of heptane and octane, given their individual vapor pressures and the amount of heptane and octane in moles.
The mole fraction can be found using Raoult's law, which states that the vapor pressure of a component in an ideal solution is proportional to the mole fraction of that component in the solution. To obtain the mole fraction of heptane vapor (xHeptane), we apply the formula:
PTotal = PHeptanexHeptane + POctanexOctane
Where PTotal is the total vapor pressure, PHeptane and POctane are the vapor pressures of pure heptane and octane respectively, and xHeptane and xOctane are the mole fractions of heptane and octane respectively.
In this case, we are given:
- Vapor pressure of pure heptane (PHeptane) = 0.0562 atm
- Vapor pressure of pure octane (POctane) = 0.0145 atm
- Amount of heptane = 0.300 mol
- Amount of octane = 0.700 mol
Using this data, we can find the total vapor pressure and then solve for the mole fraction of heptane in the vapor phase.