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11/09/2020 12:14 pm
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Heptane and octane form an ideal solution. At 373 K, the vapour pressures of the two liquid components are 105.2 kPa and 46.8 kPa respectively. What will be the vapour pressure of a mixture of 26.0 g of heptane and 35 g of octane?
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11/09/2020 12:17 pm
The molar masses of heptane and octane are 100 g/mol and 114 g/mol respectively.
26 g of heptane corresponds to 26/100 = 0.26 moles
35 g of octane corresponds to 35/114 = 0.31 moles
Mole fraction of heptane χ = 0.26/0.26 + 0.31 = 0.456
Mole fraction of octane χ′ = 1- 0.456 = 0.544
Partial pressure of heptane p = 0.456 × 105.2 = 47.97 kPa
Partial pressure of octane p′ = 0.544 × 46.8 = 25.46 kPa
Vapour pressure of solution P = p + p′ = 47.97 + 25.46 = 73.43 kPa