Answer:
0.13 atm
Explanation:
Our strategy here is to make use of Raoult´s law for ideal soultions:
P(A) = X(A)Pº(A)
where P(A) is the partial vapor pressure pressure of methanol,
X(A) is the mole fraction of solute (methanol) in solution,
Pº(A) is the vapor pressure of pure solute
Then
P(CH₃OH) = X(CH₃OH) x Pº(CH₃OH)
We do not have the mole fraction of CH₃OH, but it could be calculated from the formula:
X(A) = mol (A) / total n
total n is the number of moles of A + moles solvent
mol (CH₃3OH) = 88.2 g/ 32 g/mol = 2.76 mol CH₃OH
mol (H₂O) = 116 g/ 18 g/mol = 6.44 mol
total n = (6.44 + 2.76) mol = 9.20 mol
Now we are in position to calculate the partial pressure asked:
P(CH₃OH) = (2.76 mol CH + 9.20 mol) x 0.43 atm = 0.13 atm
( rounded to two significant figures of the least precise number , 0.43 atm ) )