Chapter 10, Problem 1RQ

Interpretation Introduction

Interpretation:

The terms molarity, molality, mass percent and mole fraction are to be explained and reason why molarity is temperature dependent and other three are temperature independent are to be given

Explanation of Solution

To explain Molarity:

Molarity can be defined as moles of solute to litres of solution.

The number of moles per litre of the solution is called as Molarity.  Molarity can be defined as the moles of solute (in grams) to the volume of the solution (in litres). The molarity of a solution can be given by the formula,

  $\text{Molarity(M)=}\frac{\text{Moles}\text{of}\text{solute(in}\text{g)}}{\text{Volume}\text{of}\text{solution(in}\text{L)}}$

To explain Molality:

Molality can be defined as moles of solute per kilogram of the solvent

The number of moles of solute per kilogram of the solvent is called as Molality.  Molality of a solution also called as molal concentration can be defined as the mass of solute in grams to the mass of the solvent in kilograms. It can be given by the equation,

  $\text{Molality(mol}{\text{kg}}^{\text{-1}}\text{)=}\frac{\text{Mass}\text{of}\text{solue(in}\text{g)}}{\text{Mass}\text{of}\text{solvent(in}\text{kg)}}$

To explain the mole fraction:

The number of moles of substance to the total number of moles is called as Mole fraction.

The number of moles of substance to the total number of moles is called as Mole fraction.  Mole fraction of a compound can be defined as the number of moles of a substance to the total number of moles present in them.  The mole fraction can be calculated by,

  $\text{Mole}\text{fraction}\text{of}\text{compound=}\frac{\text{Number}\text{of}\text{moles(in}\text{mol)}}{\text{Total}\text{number}\text{of}\text{moles(in}\text{mol)}}$

To explain mass percentage:

The ratio of calculated mass of compound to the total mass is called mass percentage.

The ratio of calculated mass of compound to the total mass is called mass percentage.  The mass percentage of a compound is ratio of calculated mass of compound to the total mass whole multiplied by 100.  The mass percentage of compound can be given by the equation.

  $\text{Mass}\text{percentage(\%)=}\frac{\text{Calculated}\text{mass(in}\text{g)}}{\text{Total}\text{mass(in}\text{g)}}\text{×100}$

To explain the reason why molarity is temperature dependent:

Volume changes with the respect to temperature.  This makes molarity temperature dependent.

To explain why other three are temperature independent:

The masses and number of moles doesn’t change with respect to temperature.  Hence, they are temperature independent.