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.
Calculate the mass percentage (% m/m) concentration of sugar in each student's solution.
For Student A: Mass of solute (sugar) = 20 g, Mass of solvent (water) = 80 g Total mass of solution = 20 g + 80 g = 100 g Mass percentage = (Mass of solute / Mass of solution) × 100 = (20 g / 100 g) × 100 = 20% m/m
For Student B: Mass of solute (sugar) = 20 g, Mass of solvent (water) = 100 g Total mass of solution = 20 g + 100 g = 120 g Mass percentage = (Mass of solute / Mass of solution) × 100 = (20 g / 120 g) × 100 = 16.67% m/m
For Student C: Mass of solute (sugar) = 30 g, Mass of solvent (water) = 80 g Total mass of solution = 30 g + 80 g = 110 g Mass percentage = (Mass of solute / Mass of solution) × 100 = (30 g / 110 g) × 100 = 27.27% m/m
Whose solution is the most concentrated? Explain why.
Student C has the most concentrated solution. The concentration of a solution is determined by the mass percentage of the solute present in it. A higher mass percentage indicates a greater amount of solute dissolved in a given amount of solvent, making the solution more concentrated. Since Student C's solution has the highest mass percentage of sugar (27.27% m/m) compared to Student A (20% m/m) and Student B (16.67% m/m), it is the most concentrated.
Explanation
The mass by mass percentage is calculated using the formula provided in the textbook: (Mass of solute / Mass of solution) × 100, where Mass of solution = Mass of solute + Mass of solvent. Applying this formula, Student A's solution is 20%, B's is 16.67%, and C's is 27.27%. The highest mass percentage indicates the highest concentration of solute in the solution.