What is dilution?

• A. Measuring the pH more accurately.
• B. Increasing the concentration by adding solute.
• C. Lowering the concentration of a solution by adding solvent.
• D. Changing solvent to improve taste.

Answer: (C)

Dilution means lowering the concentration of a solution by adding more solvent while keeping the amount of solute the same. When you add solvent, the same number of solute particles is spread out over a larger total volume, so the concentration decreases. A handy way to think about it is that the product of concentration and volume stays constant for the solute you started with (C1V1 = C2V2).

For example, if you start with 10 mL of a 1 M solution and add 10 mL of water, the total volume is 20 mL and the concentration becomes 0.5 M. If you take 1 L of a 2 M solution and dilute it to 2 L with solvent, the concentration becomes 1 M.

This is why dilution is about reducing concentration, not increasing it. The other options describe different ideas: measuring pH is about acidity, not dilution; increasing concentration by adding solute is the opposite of dilution; and changing solvent to improve taste is unrelated to the lab concept of dilution.