If molality is to be kept the same and mass of solvent is tripled, what change is needed in moles of solute?

Correct answer: Moles must be tripled

Molality is defined as moles of solute per kilogram of solvent: m = n divided by the solvent mass. If the solvent mass becomes three times larger and solute moles stay fixed, the molality becomes one-third. To preserve the original ratio, the solute amount must increase by the same factor. Thus, tripling the solvent mass requires tripling the solute moles, making option A correct.