Chapter 14, Problem 67A

Interpretation Introduction

Interpretation:

Percent by mass of MgCl₂in aqueous solution has to be calculated.

Concept introduction:

Composition of a solution can be defined by expressing its concentration. The concentrations of solutions can be expressed in different ways, which are involved in the quantity of solute and the quantity of solution or solvent. Various methods are used to describe the concentration of the solution quantitatively. Some commonly used quantitative concentration terms are percent by mass, percent by volume, molarity, molality and mole fraction.

Mass percentage or percent by mass (w/W %): The mass percentage of a component of a solution is defined as:

$\mathrm{Mass}\%ofacomponent=\frac{Mass of the component in the solution}{Total mass of the solution}\times 100$

Answer to Problem 67A

Percent by mass of MgCl₂in aqueous solution is 4.35%.

$\mathrm{Mass}\%ofacomponent=\frac{Mass of the component in the solution}{Total mass of the solution}\times 100$

Data given: Mass of MgCl₂ = 25 gm

Volume of the solvent (water) = 550 mL

Mas of the solvent water = 550 gm (As, density of water = 1 gm/mL)

Total mass of MgCl₂ solution = (550 + 25) gm = 575 gm

$\begin{array}{l}Masspercentage=\frac{Massof MgC{l}_{2}inthesolution}{Total mass of the solution}\times 100\\ Masspercentage=\frac{Massof MgC{l}_{2}inthesolution}{Total mass of the solution}\times 100\\ PercentbymassofMgC{l}_2=\frac{25gm}{575gm}\times 100=4.35\%\end{array}$

Explanation of Solution

$\mathrm{Mass}\%ofacomponent=\frac{Mass of the component in the solution}{Total mass of the solution}\times 100$

Data given: Mass of MgCl₂ = 25 gm

Volume of the solvent (water) = 550 mL

Mas of the solvent water = 550 gm (As, density of water = 1 gm/mL)

Total mass of MgCl₂ solution = (550 + 25) gm = 575 gm

$\begin{array}{l}Masspercentage=\frac{Massof MgC{l}_{2}inthesolution}{Total mass of the solution}\times 100\\ Masspercentage=\frac{Massof MgC{l}_{2}inthesolution}{Total mass of the solution}\times 100\\ PercentbymassofMgC{l}_2=\frac{25gm}{575gm}\times 100=4.35\%\end{array}$