Answer:
Mole fraction of solute (heptane) → 0.73
Explanation:
Mole fraction = Moles of solute or solvent / Total moles
Let's calculate the moles of everything:
Moles of solute → Mass of solute / Molar mass
36 g / 100 g/mol = 0.36 moles
Moles of solvent → Mass of solvent / Molar mass
16 g / 119.35 g/mol = 0.134 moles
Total moles = 0.36 + 0.134 = 0.494 moles
Mole fraction of solute = 0.36 / 0.494 → 0.73