Which of the following concentration terms is temperature independent?

(I) Molarity

(II) Molality

(III) Normality

(IV) Mole fraction

(A) I & II

(B) I & III

(C) II only

(D) II and IV

To determine which concentration terms are temperature independent, let's break down each option and analyze how temperature affects them. Concentration terms are essential in chemistry as they describe the amount of solute in a given quantity of solvent or solution. Here’s a closer look at each term:

Molarity

Molarity (M) is defined as the number of moles of solute per liter of solution. Since volume can change with temperature (due to thermal expansion), molarity is temperature dependent. As the temperature increases, the volume of the solution may expand, thus affecting the molarity.

Molality

Molality (m) is the number of moles of solute per kilogram of solvent. This measurement is based on mass, which does not change with temperature. Therefore, molality is considered temperature independent. This makes it particularly useful in situations where temperature fluctuations are expected.

Normality

Normality (N) is defined as the number of equivalents of solute per liter of solution. Similar to molarity, normality is also affected by changes in volume due to temperature variations. Thus, normality is temperature dependent as well.

Mole Fraction

Mole fraction is the ratio of the number of moles of a component to the total number of moles of all components in the mixture. Since it is a ratio and does not involve volume or mass that changes with temperature, mole fraction is temperature independent.

Summary of Findings

• Molarity: Temperature dependent
• Molality: Temperature independent
• Normality: Temperature dependent
• Mole Fraction: Temperature independent

Based on this analysis, the concentration terms that are temperature independent are molality and mole fraction. Therefore, the correct answer to your question is (D) II and IV.