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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.
• 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.
View Answer
(i) Using % m/m = mass of sugar mass of solution ×100 :
A = 20 100 ×100 = 20% ; B = 20 120 ×100 = 16.7% ; C = 30 110 ×100 = 27.3% .
(ii) Student C's solution is the most concentrated (27.3%), because it has the most sugar in the least amount of solution.
| Student | Sugar (solute) | Water (solvent) | Solution | % m/m |
|---|---|---|---|---|
| A | 20 g | 80 g | 100 g | 20/100 × 100 = 20 % |
| B | 20 g | 100 g | 120 g | 20/120 × 100 = 16.7 % |
| C | 30 g | 80 g | 110 g | 30/110 × 100 = 27.3 % |
| Most concentrated | — | — | — | Student C — most sugar in the least solution |
