Question

A solution of sucrose (mol. wt. 342) is prepared by dissolving 68.4 g of it per litre of solution. What is the osmotic pressure at 300 K? 

(R = 8.314 k Pa dm³ K⁻¹ mol⁻¹)

Answer 1

Given: Mass of sucrose = 68.4 g

Molar mass of sucrose = 342 g/mol

Volume of solution = 1 L = 1 dm³

π = CRT    ...(i)

Where,

π = Osmotic pressure (in k Pa, since R is in k Pa · dm³ · K⁻¹·mol⁻¹)

C = Molarity of solution (mol/dm³)

R = 8.314 k Pa dm³ K⁻¹ mol⁻¹

T = 300 K

C = `68.4/342`    ...[From eqn. (i)]

C = 0.2 mol/dm³

π = 0.2 × 8.314 × 300

= 498.84 k Pa