Question

3 a student in a laboratory wants to increase the concentration of salt in salt water. what is one correct way to achieve this effect? a freeze the solution, which increases the volume of the solution b agitate the solution c heat the solution, causing some of the solvent to evaporate d add more water to the solution to dilute it

Explanation:

• Option A: Freezing the solution increases the volume. According to the formula for concentration \(C=\frac{n}{V}\) (where \(n\) is the amount of solute and \(V\) is the volume of the solution), an increase in \(V\) will decrease the concentration.
• Option B: Agitating the solution only helps in the dissolution process (if the salt is not fully dissolved initially) but does not change the amount of solute or solvent in a way that increases the concentration of the salt - water solution.
• Option C: Heating the solution causes some of the solvent (water) to evaporate. Using the formula \(C = \frac{n}{V}\), when the volume \(V\) (of the solution, since \(V\) of the solution is related to the amount of solvent) decreases (because solvent evaporates) and the amount of solute \(n\) (salt) remains the same, the concentration \(C\) increases.
• Option D: Adding more water (solvent) to the solution. Using the formula \(C=\frac{n}{V}\), when \(V\) (volume of the solution) increases (because more solvent is added) and \(n\) (amount of solute) remains the same, the concentration \(C\) decreases.

Answer:

C. Heat the solution, causing some of the solvent to evaporate