Answer:
83.24 mmHg.
Explanation:
- <em>The vapor pressure of the solution (Psolution) = (Xmethanol)(P°methanol).</em>
where, Psolution is the vapor pressure of the solution,
Xmethanol is the mole fraction of methanol,
P°methanol is the pure vapor pressure of methanol.
- We need to calculate the mole fraction of methanol (Xmethanol).
<em>Xmethanol = (n)methanol/(n) total.</em>
where, n methanol is the no. of moles of methanol.
n total is the total no. of moles of methanol and urea.
- We can calculate the no. of moles of both methanol and urea using the relation: n = mass/molar mass.
n of methanol = mass/molar mass = (56.9 g)/(32.04 g/mol) = 1.776 mol.
n of urea = mass/molar mass = (7.38 g )/(60.06 g/mol) = 0.123 mol.
∴ Xmethanol = (n)methanol/(n) total = (1.776 mol)/(1.776 mol + 0.123 mol) = 0.935.
<em>∴ Psolution = (Xmethanol)(P°methanol)</em> = (0.935)(89.0 mmHg) =<em> 83.24 mmHg.</em>
