van der Waals Equation — Predicted 2026

AI-Predicted Question Angles for UPSC 2026

Based on trend analysis, current affairs, and recurring themes in van der Waals Equation.

Comparative analysis of 'a' and 'b' for different gases

high

NEET frequently tests the ability to compare properties. A question might present a table of 'a' and 'b' values for several gases and ask to identify the gas with the strongest intermolecular forces, largest molecular size, or easiest liquefaction. This tests both recall of what 'a' and 'b' represent and the ability to interpret data. Students should be prepared to rank gases based on these constants.

Conceptual questions on the conditions for ideal gas behavior and deviations

high

Understanding when and why real gases deviate from ideal behavior is a core concept. Questions could ask about the specific conditions (high T, low P) that favor ideal behavior, or conversely, the conditions where 'a' or 'b' terms become dominant, leading to significant deviations. This often involves linking the van der Waals equation to the compressibility factor (Z) and its behavior.

Application of critical constant formulas ($T_c, P_c, V_c$)

medium

While direct calculation might be less frequent, questions testing the qualitative or simple quantitative relationships between 'a', 'b', and the critical constants are probable. For instance, a question might ask how doubling 'a' or 'b' would affect $T_c$ or $P_c$, or which gas has a higher critical temperature given their 'a' and 'b' values. Understanding the physical significance of critical constants is also key.

Units of 'a' and 'b' and their derivation

low

While knowing the units is important, a direct question asking for the derivation of units is less common. However, it could be part of a multi-concept MCQ where one option tests unit correctness. Students should be able to quickly deduce the units from the equation itself.