Behaviour of Real Gases — Predicted 2026

AI-Predicted Question Angles for UPSC 2026

Based on trend analysis, current affairs, and recurring themes in Behaviour of Real Gases.

Comparative analysis of van der Waals constants 'a' and 'b' for different gases.

high

NEET frequently tests the understanding of molecular properties and their manifestation in macroscopic behavior. Questions asking to compare 'a' (intermolecular forces) or 'b' (molecular size) for a given set of gases (e.g., $H_2, O_2, NH_3, CO_2$) are very common. This requires students to recall concepts of polarity, hydrogen bonding, and molecular size. For instance, $NH_3$ would have a higher 'a' due to hydrogen bonding, while a larger molecule like $C_4H_{10}$ would have a higher 'b' than $CH_4$. This angle combines knowledge of intermolecular forces with real gas behavior.

Interpretation of Z vs. P graphs for various gases at different temperatures.

medium

Graphical questions are a staple in NEET, testing conceptual understanding visually. A common question type involves presenting a Z vs. P graph and asking to identify the gas, the temperature conditions (e.g., above or below Boyle temperature), or explaining specific deviations (e.g., why Z dips below 1 and then rises, or why H2/He always show Z>1). This requires a deep understanding of how attractive forces and molecular volume influence Z under varying conditions.

Numerical problems involving calculation of critical constants ($T_c, P_c, V_c$) from van der Waals constants 'a' and 'b', or vice-versa.

high

The relationships between critical constants and van der Waals constants are direct and formulaic, making them ideal for numerical problems. Questions often provide 'a' and 'b' and ask for $T_c$ or $P_c$, or provide $T_c$ and $P_c$ and ask for 'a' or 'b'. These problems test both formula recall and algebraic manipulation skills. Given the emphasis on problem-solving in NEET, this type of question is highly probable and requires precise calculation and unit handling.