Chapter 14, Problem 66A

Interpretation Introduction

Interpretation:

The difference between molarity and molality have to be explained.

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.

Molality: Molality (m) can be defined as the number of moles of the solute per kilogram (kg) of the solvent and it is expressed as:

$\mathrm{Molality}ofthesolution=\frac{Numberofmolesof the solute}{Massof the solvent(inkg)}$

Answer to Problem 66A

Chemist will describe a solution in terms of molality when temperature changes are expected. Molality presented concentration as moles of solute per kilogram of solvent. Molality of the solution does not depend upon the temperaturebecause volume is related to the temperature and the mass does not depend on temperature.

Molality: Molality (m) can be defined as the number of moles of the solute per kilogram (kg) of the solvent and it is expressed as:

$\mathrm{Molality}ofthesolution=\frac{Numberofmolesof the solute}{Massof the solvent(inkg)}$

If the solution undergoes temperature change that could change volume of the solvent. Molality is the ideal method of expressing concentration because the mass of solute and solvent in a solution does not change. Molality does not depend upon the temperature of the solution whereas molarity are function of temperature. Because volume is related to the temperature and the mass does not depend on temperature.

Explanation of Solution

Molality: Molality (m) can be defined as the number of moles of the solute per kilogram (kg) of the solvent and it is expressed as:

$\mathrm{Molality}ofthesolution=\frac{Numberofmolesof the solute}{Massof the solvent(inkg)}$

If the solution undergoes temperature change that could change volume of the solvent. Molality is the ideal method of expressing concentration because the mass of solute and solvent in a solution does not change. Molality does not depend upon the temperature of the solution whereas molarity are function of temperature. Because volume is related to the temperature and the mass does not depend on temperature.