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Answer:
0.3
Explanation:
Molar mass of benzene = 78 g/mol
Molar mass of heptane = 100 g/mol
number of moles of heptane = 59 g/100 g/mol = 0.59 moles
number of moles of benzene = 103 g/78 g/mol = 1.32 moles
Total number of moles = 0.59 + 1.32 = 1.91 moles
Mole fraction of heptane = 0.59/1.91 = 0.31