Chapter 15, Problem 17A

Interpretation Introduction

Interpretation:

Mass of heptane and pentane present in 93 gm of the solution have 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 17A

4.84 gm of heptane and 2.7 gm of pentane are present in 93 gm of a solution.

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

Data given: Total mass of the solution = 93 gm

Percent by mass heptane = 5.2%

  $\begin{array}{l}Percentbymassheptane=\frac{Massof heptane}{Total mass of thesolution}\times 100\\ Massof heptane=\frac{Percentbymassheptane\times Total mass of thesolution}{100}\\ Massof heptane=\frac{5.2\times 93gm}{100}=4.84gm\end{array}$

Percent by mass pentane = 2.9%

  $\begin{array}{l}Percentbymasspentane=\frac{Massof pentane}{Total mass of thesolution}\times 100\\ Massof pentane=\frac{Percentbymasspentane\times Total mass of thesolution}{100}\\ Massof pentane=\frac{2.9\times 93gm}{100}=2.7gm\end{array}$

Explanation of Solution

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

Data given: Total mass of the solution = 93 gm

Percent by mass heptane = 5.2%

  $\begin{array}{l}Percentbymassheptane=\frac{Massof heptane}{Total mass of thesolution}\times 100\\ Massof heptane=\frac{Percentbymassheptane\times Total mass of thesolution}{100}\\ Massof heptane=\frac{5.2\times 93gm}{100}=4.84gm\end{array}$

Percent by mass pentane = 2.9%

  $\begin{array}{l}Percentbymasspentane=\frac{Massof pentane}{Total mass of thesolution}\times 100\\ Massof pentane=\frac{Percentbymasspentane\times Total mass of thesolution}{100}\\ Massof pentane=\frac{2.9\times 93gm}{100}=2.7gm\end{array}$