Question

5 moles of sucrose (molecular mass = 342 g mol⁻¹) dissolved in 1000 g of water (molecular mass = 18 g mol⁻¹). Vapour pressure of pure water at 298 K = 4.57 mm Hg.

What will be the mole fraction of sucrose in water?

Options

• 0.8261

• 0.0826

• 0.4376

• 0.0435

Answer 1

0.0826

Explanation:

Given: Moles of sucrose = 5 mol

Mass of water = 1000 g

Molar mass of water = 18 g/mol

Moles of water = `1000/18` = 55.56 mol

`chi_"sucrose" = 5/(5 + 55.56)`

= `5/60.56`

= 0.0826