You have 200.0 mL of 0.150 M aqueous NH4Cl. Which of the following statements is true?

• A. If you add water to the solution, the molarity will increase.
• B. Water is the solute.
• C. If you add water to the solution, the molarity will decrease.
• D. NH4Cl is the solute.

Answer: (D)

Verified step by step guidance

1. Understand the concept of molarity: Molarity (M) is defined as the number of moles of solute per liter of solution. It is expressed as M = \( \frac{\text{moles of solute}}{\text{liters of solution}} \).
2. Consider the effect of adding water to the solution: When you add water to a solution, you are increasing the volume of the solution while keeping the amount of solute constant. This results in a decrease in molarity because the denominator in the molarity equation (liters of solution) increases.
3. Analyze the statement 'If you add water to the solution, the molarity will increase': This statement is incorrect because adding water increases the volume, thus decreasing the molarity.
4. Identify the solute and solvent: In a solution, the solute is the substance that is dissolved, and the solvent is the substance that does the dissolving. In this case, NH4Cl is the solute, and water is the solvent.
5. Evaluate the statement 'Water is the solute': This statement is incorrect because NH4Cl is the solute, not water. Water is the solvent in this aqueous solution.