Differentiate between molarity and molality of a solution.

Molarity and molality are both measures of concentration in solutions, but they are defined differently:

1. Molarity (M):

   • Molarity is defined as the number of moles of solute dissolved in one liter of solution.
   • It is expressed in moles per liter (mol/L or M).
   • Mathematically, it is represented as:
     Molarity(M)=moles of solutevolume of solution (in liters)Molarity(M)=volume of solution (in liters)moles of solute

2. Molality (m):

   • Molality is defined as the number of moles of solute dissolved in one kilogram of solvent.
   • It is expressed in moles per kilogram (mol/kg or m).
   • Mathematically, it is represented as:
     Molality(m)=moles of solutemass of solvent (in kg)Molality(m)=mass of solvent (in kg)moles of solute

Key Differences:

1. Dependency on Volume vs. Mass:

   • Molarity depends on the volume of the solution, while molality depends on the mass of the solvent. Molarity can change with temperature due to changes in volume, but molality remains constant because it's based on the mass of the solvent.

2. Temperature Sensitivity:

   • Molarity changes with temperature because volume changes with temperature (due to thermal expansion or contraction), whereas molality is unaffected by temperature changes as it is based on the mass of the solvent, which typically does not change significantly with temperature.

3. Applications:

   • Molarity is commonly used in laboratory settings and in chemical reactions where solutions are prepared by adding solute to a specific volume of solvent.
   • Molality is often used in situations where temperature changes are expected or in calculations involving colligative properties (such as boiling point elevation and freezing point depression), where the number of particles in the solvent is crucial.

In summary, while both molarity and molality measure the concentration of a solution, they differ in their dependence on volume or mass and in their temperature sensitivity, making each useful in different contexts.