Question

(a) What do you mean by the concentration of a solution? Discuss any three methods of expressing the concentration of a solution.
(b) A solution contains 30 g of sugar dissolved in 300 g of water. Calculate the concentration of this solution.

Answer 1

(a) Concentration of a solution is defined as the amount of solute that is present in a given amount of solution.
It can be expressed in terms of:

• Mass by the mass percentage of a solution $=\frac{\text{mass of solute}}{\text{mass of solution}}\times 100$
• Mass by the volume percentage of a solution $=\frac{\text{mass of solute}}{\text{mass of solution}}\times 100$
• Volume by the volume percentage of a solution $=\frac{\text{volume of solute}}{\text{volume of solution}}\times 100$

(b) Mass of sugar (solute) = 30 g
Mass of water (solvent) = 300 g
So, the mass of solution = mass of solute + mass of solvent
= (30 + 300) g
= 330 g

Now, Mass by the mass percentage of a solution $=\frac{\text{mass of solute}}{\text{mass of solution}}\times 100$
$=\frac{\text{30 g}}{\text{330 g}}\times 100$
= 9.09 %