Question

What is the vapor pressure of the pure solvent if the vapor pressure of a solution of 15g sucrose (C12H22O11) in 100g of ethanol (C2H5OH) is 58 mmHg?

Answer 1

Molar mass of sucrose = 342g/mol

Moles of sucrose = $\frac{15}{342}=0.04386$

Molar mass of ethanol= 46g/mol

Moles of ethanol= 100/46=2.1739

Total moles = 0.04386+2.1739=2.21776

Mole fraction of ethanol = 2.1739/2.21776=0.98022

$58=0.98022×P_{ethanol}$

$P ethanol ​ =59.17mmHg$