Question

Three students, A, B and C, are preparing sugar solutions for an experiment:

• Student A dissolves 20 g of sugar in 80 g of water.
• Student B dissolves 20 g of sugar in 100 g of water.
• Student C dissolves 30 g of sugar in 80 g of water.

(i) Calculate the mass percentage (% m/m) concentration of sugar in each student’s solution.

(ii) Whose solution is the most concentrated? Explain why.

Answer 1

(i) Mass by mass percentage = `"mass of solute"/"mass of solution" xx 100`

Student A:

Mass of solution = 20 g + 80 g = 100 g

% m/m = `20/100 xx 100 = 20` % m/m

Student B:

Mass of solution = 20 g + 100 g = 120 g

% m/m = `20/120 xx 100 = 16.67` % m/m

Student C:

Mass of solution = 30 g + 80 g = 110 g

% m/m = `30/110 xx 100 = 27.27` % m/m

(ii) Due to its highest mass percentage of sugar (27.27% m/m), Student C’s solution is the most concentrated.