JEE Main 2024 — Some Basic Concepts Of Chemistry Question with Solution

The quantity that changes with temperature from the given options is Molarity.

Molarity, which is denoted with a capital M, measures the number of moles of solute dissolved in one liter of solution. It is expressed as:

$$Molarity(M)=\frac{molesofsolute}{litersofsolution}$$

Since the volume of liquids expands or contracts with temperature, the volume of the solution will change as the temperature changes, which in turn will affect the molarity. For example, if the temperature of a solution increases, its volume may expand. If the number of moles of solute remains constant, the increased volume will result in a decreased molarity because the solute is now dispersed in a greater volume of solution.

In contrast, other measures of concentration such as:

Molality, which is measured as the number of moles of solute per kilogram of solvent (not affected by temperature since it's based on mass, not volume),

$$Molality(m)=\frac{molesofsolute}{kilogramsofsolvent}$$

Mole fraction, which is the ratio of the number of moles of one component to the total number of moles of all components in the solution (also not affected by temperature since the ratio of moles doesn't change with temperature),

$$Molefraction(X)=\frac{molesofcomponent}{totalmolesinmixture}$$

and Mass percentage, which is the percentage by mass of a component in a mixture (again, not affected by temperature because it's based on mass),

Mass \ percentage \(%) $$=\frac{massofcomponent}{totalmassofmixture}\times 100\%$$

do not change with temperature. Therefore, the correct answer to the question is:

Option B : Molarity