If a solution contains 0.5 moles of solute and 4.5 moles of solvent for a total of 5.0 moles, what is the mole percent of solute?

• A. 5%
• B. 50%
• C. 10%
• D. 0.5%

Answer: (C)

Mole percent is the fraction of the total moles that a component contributes, times 100. With 0.5 moles of solute in a total of 5.0 moles, the calculation is (0.5 / 5.0) × 100 = 10%. So solute makes up 10% of the particles in the mixture (the solvent would be 4.5/5.0 × 100 = 90%). This is a mole-based measure, not dependent on mass.