Differentiate between molarity and molality of a solution. How can we change molality value of a solution into molarity value? (Comptt. Delhi 2014)

Molarity and molality are both measures of the concentration of a solution.

1. Molarity (M) is defined as the number of moles of solute per liter of solution. It is expressed in moles per liter (mol/L). Molarity depends on the volume of the solution, which can change with temperature due to the expansion or contraction of the solution.

2. Molality (m) is defined as the number of moles of solute per kilogram of solvent. It is expressed in moles per kilogram (mol/kg). Molality does not depend on temperature as it is based on the mass of the solvent, which does not change with temperature.

To convert molality to molarity, you can use the following formula:

M = m * (density of the solution in g/mL) / (molar mass of the solute in g/mol)

This formula assumes that the density of the solution is approximately equal to the density of the solvent, which is a reasonable approximation for dilute solutions.

Here are the steps to convert molality to molarity:

1. Multiply the molality by the density of the solution. This gives you the number of moles of solute per milliliter of solution.

2. Divide this number by the molar mass of the solute to get the molarity. This gives you the number of moles of solute per liter of solution.

Remember to use the correct units in your calculations. The density should be in grams per milliliter (g/mL) and the molar mass should be in grams per mole (g/mol).