Which statement correctly contrasts mass percent and mole percent in a solution?

• A. Mass percent uses mass of solute per total mass of solution; mole percent uses moles of solute per total moles of solution.
• B. Mass percent uses mass of solute per total mass; mole percent uses moles of solute per total moles.
• C. Mass percent uses moles of solute per total mass; mole percent uses mass of solute per total moles.
• D. Mass percent uses mass of solvent per total mass; mole percent uses moles of solvent per total moles.

Answer: (A)

Mass percent and mole percent express how much of a component sits in the whole solution, but they use different bases. Mass percent is the mass of the solute divided by the total mass of the solution, multiplied by 100. Mole percent is the amount in moles of the solute divided by the total moles of all components in the solution, multiplied by 100. So the best description is that mass percent uses mass relative to the total mass of the solution, while mole percent uses moles relative to the total moles of the solution. The other ways to phrase it either switch mass and moles, refer to the solvent instead of the whole solution, or mix up the basis, which is why they’re not correct.