Question

What is the vapor pressure of the pure solvent if the vapor pressure of a solution of 10 g of sucrose (C6H12O6) in 100 g of ethanol (C2H6O) is 55 mmHg?​

Answer 1

The vapor pressure of the pure solvent will be equal to 55.7 mmHg.
You're dealing with a solution of sucrose, which is your solute, dissolved in ethanol, which is your solvent.
Since sucrose is a non-volatile solute, the vapor pressure of the solution can be expressed using the mole fraction of the solvent - this is known as Raoult's Law.
P
solution
=
χ
solvent
⋅
P
∘
solvent
, where
P
solution
- the vapor pressure of the solution;
χ
solvent
- the mole fraction of the solvent;
P
∘
solvent
- the vapor pressure of the pure solvent.