Chapter 15.2, Problem 4RQ

Interpretation Introduction

Interpretation: Number of moles of sucrose in $750\text{mL}$ of a $0.250\text{M}$ of sugar has to be determined.

Concept introduction: Molarity is a concentration term that is defined as the number of moles of solute dissolved in one litre of the solution. It is denoted by M, and its unit is mol/L.

  $\text{Molarity }=\frac{\text{amount}\left(\text{mol}\right)\text{of}\text{solute}}{\text{volume }\left(\text{L}\right)\text{of solution}}$

Answer to Problem 4RQ

Number of moles of sucrose in $750\text{mL}$ of a $0.250\text{M}$ of sugar is $0.1875\text{M}$ .

Explanation of Solution

Given information: Volume and molarity of sucrose is $750\text{mL}$ and $0.250\text{M}$ , respectively.

Molarity of sucrose solution is calculated by formula as follows:

  $\text{Molarity of sucrose}=\frac{\text{number of moles of sucrose }}{\text{volume}\text{of sucrose}}$

Rearrange above equation to calculate number of moles of sucrose.

  $\text{number of moles of sucrose}=\text{Molarity of sucrose}\times \text{volume}\text{of sucrose}$

Substitute $0.250\text{M}$ for molarity of sucrose and $750\text{mL}$ for Volume of sucrose in above equation.

  $\begin{array}{c}\text{number of moles of sucrose}=\text{Molarity of sucrose}\times \text{volume}\text{of sucrose}\\ =0.250\text{M}\times 750\text{mL}\left(\frac{1\text{L}}{1000\text{mL}}\right)\\ =0.1875\text{M}\end{array}$

Conclusion

Number of moles of sucrose in $750\text{mL}$ of a $0.250\text{M}$ of sugar is $0.1875\text{M}$ .