What does concentrated mean in a solution?

• A. A solution that contains a large number of solute particles or a small amount of water
• B. A solution with a high pH
• C. A solution with a low boiling point
• D. A solution that contains many solvent molecules

Answer: (A)

Concentration is about how much solute is dissolved in a given amount of solvent. A concentrated solution has a lot of solute compared with the amount of solvent, or very little solvent for the amount of solute. That’s exactly what the statement describes: a solution with a large number of solute particles or a small amount of water.

Think of making syrup by dissolving a lot of sugar in water—that’s concentrated. If only a tiny amount of sugar is used, the solution is dilute. The other ideas aren’t about how much stuff is dissolved: a high pH is about acidity or basicity, not how much solute is present; a low boiling point isn’t a defining feature of concentration (in fact adding solute can raise the boiling point in many cases); having many solvent molecules would imply lots of solvent relative to solute, which is dilute, not concentrated.