Question

Differentiate between molarity and molality of a solution. How can we change the molality value of a solution into a molarity value?

Answer 1

Part: 1: Differentiate between Molarity and Molality:

Molarity	Molality
1. Molarity of solution is defined as the total number of moles of solute present per litre of solution.	1. Molality is defined as the total moles of a solute present per kilogram of solvent.
2. Mathematical expression is M = number of moles of the solute /Volume of solution in litres. $\mathrm{M}=\frac{\mathrm{n}}{\mathrm{V}}$	2. The mathematical expression is m = Numbers of moles of solute/Mass of solvent in Kg. $\mathrm{m}=\frac{(\mathrm{g}✕1000)}{(\mathrm{W}✕\mathrm{m})}$
3. Molarity has a unit of mol L-1.	3. Molality has a unit of mol Kg-1.
4. It depends on the volume of the solution.	4. It depends on the mass of the solvent.
5. Molarity is affected by the change in temperature.	5. Molality has no effect on temperature.

Part: 2: The relationship between the molarity (M) and molality (m) is expressed as below:

$$\begin{gathered} \mathrm{m}=\frac{(1000\times \mathrm{M})}{1000\times (\mathrm{d}-\mathrm{M})\times \mathrm{M}\text{'}} \\ \mathrm{M}=\mathrm{Molarity} \\ \mathrm{m}=\mathrm{Molality} \\ \mathrm{M}\text{'}=\mathrm{Molar}\mathrm{mass}\mathrm{of}\mathrm{the}\mathrm{solute} \end{gathered}$$

By the formula, the molality value of a solution changed into the molarity value by the provided formula.