Which of the following operations yields the number of moles of solute in a solution?

• A. Dividing the molarity (in mol/L) by the volume of solution (in liters)
• B. Multiplying the volume of solution (in liters) by the molarity (in mol/L)
• C. Dividing the mass of solute (in grams) by its molar mass (in g/mol)
• D. Multiplying the mass of solute (in grams) by its molar mass (in g/mol)

Answer: (C)

Verified step by step guidance

1. Recall that molarity (M) is defined as the number of moles of solute per liter of solution, expressed as \(M = \frac{\text{moles of solute}}{\text{volume of solution in liters}}\).
2. To find the number of moles of solute from molarity and volume, rearrange the formula to solve for moles: \(\text{moles of solute} = M \times V\), where \(V\) is the volume in liters.
3. Understand that dividing molarity by volume, \(\frac{M}{V}\), does not give moles because the units would be \(\frac{\text{mol/L}}{L} = \text{mol}/L^2\), which is not meaningful for moles.
4. Recognize that the number of moles can also be found by dividing the mass of solute (in grams) by its molar mass (in g/mol), using the formula \(\text{moles} = \frac{\text{mass}}{\text{molar mass}}\).
5. Note that multiplying the mass of solute by its molar mass would give units of grams squared per mole, which is not a valid way to find moles.