Chapter 16.2, Problem 20LC

Interpretation Introduction

Interpretation: To compare the number of moles of solute before and after dilution.

Concept introduction: Dilution is the process in which the concentrated solution is made less concentrated. This is done by the addition of solvent in the solution.

Answer to Problem 20LC

The total number of moles of solute before and after dilution remains the same.

Explanation of Solution

Concentrated solutions are those in which the amount of solute is more in a given quantity of solution whereas, diluted solutions are those in which the amount of solute is less in a given quantity of solution. The process of dilution is to make a diluted solution from a concentrated solution.

In dilution, the total number of moles of solute before and after dilution remains the same but the number of moles of solute per unit volume decreases in the diluted solution.

The equation for dilution can be described as:

  $\text{Molarity(}M\text{) = }\frac{\text{Number of moles of solute (}n\text{)}}{\text{Volume of solution (in }L\text{)}}$

If the number of moles remains constant throughout dilution, the number of moles can be written as:

  $n=M\times V$

No. of moles of solute before dilution = No. of moles of solute after dilution.

  $M1V1=M2V2$

Where:

  $M1$ is the initial molarity.

  $V1$ is the initial volume.

  $M2$ is the final molarity.

  $V2$ is the final volume.

Conclusion

The total number of moles of solute before and after dilution remains the same.