A solution is prepared by dissolving 40.0 g of sucrose, in 250 g of water at 25°C. What is the vapor pressure of the solution if the vapor pressure of water at 25°C is 23.76 mm Hg?

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Answer 1 · 2017-02-15T16:34:41

$23.6mmHg$

Use Raoults Law

$p_{i}=p_{i}^{\star }x_{i},$

$" Calculate number of moles in each of the substance"$

$"Mol of H20 = 250 g H2O * 1 mol/18.02 g H2O = 13.9 mol H2O"$

$"Mol C12H22O11 = 40.0 g C12H22O11 * 1 mol/342.296 g = 0.12 mol sucrose"$

Now calculate vapour pressure

$"Mole fraction H2O = 13.9 mol H_2O/(0.12 mol+ 13.9 mol) = 0.991"$

$"Partial pressure of soln = 0.991 * 23.76 = 23.546 mm Hg"$