Solubility of Gas in Liquids — NEET Importance

NEET Importance Analysis

The topic of 'Solubility of Gas in Liquids' is of significant importance for the NEET UG examination, primarily falling under the 'Solutions' chapter in Physical Chemistry. Questions from this subtopic appear with moderate frequency, typically ranging from 1 to 2 questions per year, contributing 4 to 8 marks. The questions are predominantly conceptual or numerical applications of Henry's Law.

Common Question Types:

1
Direct application of Henry's Law: — Calculating mole fraction, partial pressure, or Henry's constant given other parameters. These are straightforward numerical problems.
2
Qualitative effects of temperature and pressure: — Questions asking how solubility changes with increasing/decreasing temperature or pressure, often linked to Le Chatelier's Principle.
3
Real-world applications: — Scenarios like carbonated drinks, deep-sea diving (decompression sickness), or high-altitude sickness (anoxia) are frequently used to test conceptual understanding.
4
Comparison of gas solubilities: — Questions asking to compare the solubility of different gases based on their nature (polarity, size, reactivity) or to identify which gas has the highest/lowest Henry's constant.

Mastering this topic requires a clear understanding of Henry's Law, its mathematical form, its limitations, and the qualitative effects of temperature and the nature of the gas and solvent. Students must be proficient in unit conversions, especially for pressure, as $K_H$ values can be given in various units (atm, bar, kPa, mmHg).

Vyyuha Exam Radar — PYQ Pattern

Analysis of previous year NEET questions on 'Solubility of Gas in Liquids' reveals a consistent pattern. Henry's Law is the most frequently tested concept, often appearing as direct numerical problems where students need to calculate mole fraction, partial pressure, or $K_H$.

These numerical questions typically involve simple calculations but require careful unit conversion (e.g., kBar to atm, or Pa to atm). Another common pattern involves conceptual questions on the effect of temperature, often linked to real-world scenarios like aquatic life or thermal pollution.

Questions about the 'bends' in deep-sea diving and anoxia at high altitudes are also recurring. The difficulty level for these questions is generally easy to medium, making them scoring opportunities if the core concepts and formulas are clear.

Less frequent but still important are questions comparing the solubility of different gases based on their molecular properties (polarity, size, reactivity) or asking about the limitations of Henry's Law.

There's a clear emphasis on understanding the inverse relationship between $K_H$ and solubility. Students should expect at least one question from this subtopic, making it a high-yield area.