Chapter 16.2, Problem 27LC

Interpretation Introduction

Interpretation: The information needed to convert molarity to percent by volume is to be described.

Concept introduction: Molarity and percent by mass are the ways by which concentration can be measured. The concentration of a solution is defined as the amount of solute present in the given quantity of solvent.

Answer to Problem 27LC

The information required to convert molarity to percent by volume is the molar mass of solute and density.

Explanation of Solution

The formula of molarity is described as follows:

  $\text{Molarity = }\frac{n}{V}$

Where:

n is the number of moles of solute.

V is the volume of the solution.

Now, the formula of percent by volume is described as follows:

  $\text{Percent by volume = }\frac{\text{Volume of solute}}{\text{Volume of solution}}\times 100$

To calculate the percent by volume from molarity, two pieces of information is needed and those are as follows:

• Molar mass of solute.
• Density.

The molar mass of the solute and density are needed to find out the volume of the solute then only, percent by volume can be determined. The formula of density is as follows:

  $\text{Density = }\frac{\text{Mass}}{\text{Volume}}$

From molarity number of moles can be easily calculated and then from the number of moles, the given mass of solute can be calculated. This is illustrated below:

  $n=\frac{\text{Given mass}}{\text{Molar mass}}$

From here, mass is calculated, and hence, substitute in the density formula to calculate the volume of the solute.

Therefore, percent by mass can be calculated from molarity if two pieces of information are available and those are the molar mass of solute and density.

Conclusion

The information required to convert molarity to percent by volume is the molar mass of solute and density.