Factors Affecting Solubility of Gases - NEET Notes, Formula & Common Mistakes
Solubility of GasesSolutionsNEET ChemistryNEET 2025Henry's LawFactors affecting solubility
Factors Affecting Solubility of Gases - NEET Notes, Formula & Common Mistakes
Solutions·2 min read·NEET 2026
What NEET Asks
Conceptual questions on effects of temperature and pressure on gas solubility are common.
Direct applications of Henry's Law (p = K_H * x) for calculations involving mole fraction or partial pressure.
Comparison of solubility for different gases or at varying conditions. Expect 1-2 questions from the Solutions chapter.
Key Points
Temperature Effect: Solubility of gases in liquids decreases with increasing temperature. This is because dissolution of gases is generally an exothermic process (ΔH < 0), favoring the reverse (undissolved gas) at higher temperatures.
Pressure Effect (Henry's Law): Solubility of a gas in a liquid is to the partial pressure of the gas above the liquid. Higher pressure, higher solubility.
directly proportional
Henry's Law Formula: p = K_H * x, where p is partial pressure of the gas, K_H is Henry's Law constant, and x is the mole fraction of the gas in the solution.
Henry's Law Constant (K_H): Varies with the nature of the gas and solvent, and temperature. Higher K_H indicates lower solubility of the gas at a given partial pressure.
Nature of Gas: Gases that react chemically with the solvent (e.g., NH₃ in H₂O forming NH₄OH) or can form H-bonds are significantly more soluble than non-reacting gases (e.g., N₂, O₂).
Must-Know Formula / Reaction
Henry's Law:p = K_H * x
p: Partial pressure of the gas (atm or bar)
K_H: Henry's Law constant (atm or bar/mole fraction)
x: Mole fraction of the gas in the solution (dimensionless)
Common Mistakes
Students often confuse the effect of temperature on gas solubility (decreases) with solid solubility (usually increases).
Don't confuse a high K_H value with high solubility; remember, K_H is inversely related to solubility at a given pressure.
Assuming Henry's Law is universally applicable; it works best for dilute solutions and low pressures, and for gases that do not react with the solvent.
Rapid Revision
Gas solubility decreases with temperature and increases with pressure (Henry's Law, p=K_H*x). Higher K_H means lower solubility. Remember reactive gases like NH₃ are exceptions to ideal Henry's Law behavior.
Frequently Asked Questions
Why does gas solubility decrease with increasing temperature?▾
Dissolution of gases in liquids is an exothermic process. According to Le Chatelier's principle, increasing the temperature shifts the equilibrium towards the endothermic direction, which is the desorption of gas, thus decreasing solubility.
What is Henry's Law and its significance?▾
Henry's Law states that the partial pressure of the gas in vapor phase (p) is proportional to the mole fraction of the gas (x) in the solution: p = K_H * x. It's significant for understanding how pressure affects the solubility of gases in liquids, crucial for phenomena like soda fizziness and deep-sea diving.
How does the nature of gas affect its solubility in water?▾
Gases that can react chemically with water (e.g., NH3, SO2, CO2) or form hydrogen bonds with water molecules are significantly more soluble than inert gases (e.g., N2, O2, He) which interact primarily through weaker van der Waals forces.
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