Question

A solution contains 0.5 moles of MgSO4 dissolved in 0.6 liters of water. In water MgSO4 dissociates into one Mg2 particle and one SO42- particle. What is the osmolarity of the solution?

Answer 1

Answer:

1.7 Osm/L  

Explanation:

Osmotic concentration is the number of osmoles (Osm) of solute per litre of solution .

$\text{Osmotic concentration} = \dfrac{\text{No. of osmoles }}{\text{Litres of solution}}$

An osmole is the number of moles of solute that contribute to the osmotic pressure of a solution.

1 Osm = i × n, where

i = the van't Hoff i factor and

n = the number of moles

The van't Hoff i factor is the number of solute particles obtained from 1 mol of solute.

For example,  

MgSO₄(aq) ⟶ Mg²⁺(aq) + SO₄²⁻(aq)

1 mol of MgSO₄ produces 2 mol of ions in solution, so i = 2.

$\text{Osmotic concentration} = \dfrac{\text{1.0 Osm}}{\text{0.6 L}} = \textbf{1.7 Osmol/L}$