Molality = No. of moles of solute / kg of solvent whereas molarity = No. of moles of solute / Litres of solvent.When temp. is changed in an aqueous solution, its volume (in litres) changes, changing the molarity whereas mass of solvent doesn't change keeping the molality constant. Hence molality is a better unit of conc. than molarity.

The only advantage molarity has over molality is in the computation after the volumetric titration. The volume (in ml) consumed of the molar solution can be used directly on the computation (m1)(v1) = (m2)(v2) because, molar soution is already being expressed in volume, as compared to molal solution being expressed in weight.

Advantage of Molarity over Molality as the Unit of Concentration

Introduction:
When it comes to measuring the concentration of a solution, there are various units that can be used. Two commonly used units are molarity and molality. Molarity, denoted as M, is the number of moles of solute per liter of solution, while molality, denoted as m, is the number of moles of solute per kilogram of solvent. While both units have their merits, molarity offers several advantages over molality.

1. Ease of Calculation:
Molarity is more convenient to use and calculate compared to molality. This is because molarity takes into account the volume of the entire solution, including both the solute and the solvent. Since volume is a commonly measured quantity, it is easier to determine the molarity of a solution using a simple formula: Molarity (M) = Moles of Solute / Volume of Solution (in liters). On the other hand, molality requires the measurement of the mass of the solvent, which can be more challenging and time-consuming.

2. Independence from Temperature:
Another advantage of molarity is that it is relatively independent of temperature changes, while molality is not. Molarity is based on the volume of the solution, which remains relatively constant with temperature variations. In contrast, molality is based on the mass of the solvent, which can change with temperature due to thermal expansion or contraction. Therefore, molarity is a more reliable measure of concentration when dealing with solutions at different temperatures.

3. Practicality in Laboratory Settings:
Molarity is often the preferred unit of concentration in laboratory settings due to its practicality. Laboratory equipment, such as volumetric flasks and graduated cylinders, are typically calibrated to measure volumes accurately. Therefore, it is easier to measure the volume of a solution and calculate its molarity. Additionally, many chemical reactions and experiments are designed based on molarity, making it more compatible with laboratory protocols.

4. Commonly Used in Chemical Equations:
Molarity is widely used in chemical equations and stoichiometry calculations. When balancing chemical equations or determining the quantities of reactants and products involved in a reaction, molarity is the preferred unit of concentration. It allows for a direct comparison of the amounts of different substances involved, simplifying the calculations.

Conclusion:
In summary, molarity offers significant advantages over molality as the unit of concentration. Its ease of calculation, independence from temperature, practicality in laboratory settings, and compatibility with chemical equations make it a preferred choice for most applications. However, it is important to note that the choice of concentration unit depends on the specific requirements of the experiment or application at hand.