Which of the following units can be used to express the concentration of a solution in terms of molarity?

• A. mol/kg
• B. g/L
• C. mol/L
• D. ppm

Answer: (C)

Verified step by step guidance

1. Understand that molarity is defined as the number of moles of solute per liter of solution. The general unit for molarity is therefore moles per liter, written as \(mol/L\).
2. Analyze each given unit to see if it matches the definition of molarity: \(mol/kg\) represents moles per kilogram of solvent, which is molality, not molarity.
3. The unit \(g/L\) expresses grams of solute per liter of solution, which is a concentration unit but not molarity because it is not in moles.
4. The unit \(ppm\) (parts per million) is a measure of concentration by mass or volume ratio, but it is not expressed in moles per liter, so it is not molarity.
5. Conclude that only \(mol/L\) correctly expresses concentration in terms of molarity, as it directly relates moles of solute to volume of solution.