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11/09/2020 12:23 pm
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Calculate the mass of a non-volatile solute (molar mass 40 g mol-1) which should be dissolved in 114 g octane to reduce its vapour pressure to 80%.
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11/09/2020 12:26 pm
Let p be the vapour pressure of pure octane.
The vapour pressure of solution will be 80/100p = 0.8 p.
Molar mass of solute (M) and octane (m) are 40 g/mol and 114 g/mol respectively.
Mass of octane, w is 114 g.
p - p′/p = Wm/Mw p - 0.8p/p = W × 114 /40 × 114 W = 8g
Hence, 8g of solute are required.