Chapter 14, Problem 25E

Interpretation Introduction

Interpretation:

The molality of para-dichlorobenzene in a solution needs to be determined.

Concept introduction:

Mass percent of any species in the solution can be calculated from its mass and mass of the solution. For example, if mass of the species is x and that of solution is y, the mass percent of the solution can be calculated as follows:

$\%m=\frac{x\text{ g}}{y\text{ g}}\times 100\%$

The molality of solution is defined as number of moles of solute in 1 kg of the solvent. Thus,

$m=\frac{n}{M_{\text{solvent}}\left(\text{kg}\right)}$

The density of the solution is related to mass and volume of solution as follows:

$d=\frac{m_{\text{solution}}}{V_{\text{solution}}}$

The number of moles of substance can be calculated from mass and molar mass as follows:

$n=\frac{m}{M}$

Here, m is mass and M is molar mass.