Henrys Law - Formula, Examples, Factors and FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:51 PM IST

State Henry’s law

Henry’s Law can be stated as “the amount of gas absorbed or dissolved in a liquid at constant temperature is directly proportional to the pressure exerted by the gas”.

Henry’s law formula is given below.

P ∝ C

P = kh.C

In the above mathematical equation, kh in the above equation stands for Henry’s law constant being the proportionality constant for this mathematical formula or equation where,

P = Partial Pressure exerted by the

gas on liquid (atm)

kh = Henry’s law constant.

C = Dissolved gas concentration

(mol/dm^-3)

Hence, the unit of kh becomes mol dm^-3atm^-1

The partial pressure of gas in the vapour phase is directly proportional to the mole fraction of that gas in the vapour phase.

P being the partial pressure of the gas an ‘X’ being the mole fraction, The Henry’s Law mathematical expression can also be stated as follows-

P = kh.X

William Henry - an English chemist and physician, formulated this equation in the early 19th century.

Henry’s Law Proportionality Constant is the expression used when the constant is illustrated in terms of solubility/pressure.

It is represented as ‘H’.

Henry’s Law Volatility Constant is the expression used when the constant is defined in the terms of pressure/solubility.

It is denoted by ‘kh’.

Let us take a little bit of time and think about how the pressure of the gas above a liquid can affect its solubility in that liquid.

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State Henry’s law
Examples of Henry’s Law:-
Factors Affecting Henry’s Law:-
Limitations of Henry’s law:-

Let us try to understand this law by considering the below example:-

Taking into consideration a very dilute solution, solvent molecules will act as near neighbours for solute molecules. the escaping probability of a particular solute particle or a molecule. Into the gaseous phase is predicted to be independent of the solute molecule concentration. The escaping rate of solute molecules will be directly proportional to the solute molecule concentration in the solution. Until the return rate becomes equal, the accumulation of solute molecules in the gas continues. The gas is very dilute in concentration, the return rate will be directly proportional to the partial pressure of the solute.

Thus, for a very dilute solution, at equilibrium with gas at low partial pressure, this partial pressure will be directly proportional to the quantity of gas absorbed or dissolved. This is Inferred as Henry’s law. However, this law is only applicable for dilute solutions and gases having low partial pressures where the amount of molecular species in the solution as well as in the gas is the same. Here it must be noted that the solubility of a gas in a liquid is greater provided that the partial pressure of the gas on liquid is greater.

Examples of Henry’s Law:-

Carbonated drinks –

Henry’s law holds in the case of carbonated drinks like Pepsi and coca-cola. The gas in the unopened carbonated drink above the liquid is generally carbon dioxide in pure form. This gas is kept at pressure little greater than atmospheric pressure in the bottle. So, the solubility of the carbon dioxide gas is high in an unopened drink. The pressurized carbon dioxide ( ) gas escapes into the atmosphere as soon as the bottle is reopened with a hissing sound. The decreasing partial pressure of gas in the atmosphere leads to a decrease in the solubility of the gas present in the drink.

This is because of Henry’s law. Hence, the gas dissolved arranges itself at the surface of the drink in the form of bubbles and escape into the atmosphere. The carbonated drink when kept open for a long duration reaches equilibrium with the carbon dioxide ( ) concentration in the atmosphere (0.05%) causing it to go flat (losing frizzy taste).

Related Topics Link,

Oxygenation of Blood and Respiration:-

Respiration is the process where the exchange of oxygen ( )

For carbon dioxide ( ) takes place for gaining energy from the breakdown of sugars.

This process of respiration involves the intake of oxygen called inhalation. Inhalation is a process where it is accompanied by an increase in oxygen’s partial pressure in the alveoli. When the oxygenated and deoxygenated blood comes in contact with alveoli,

Gas exchange takes place following henry’s law.

Oxygen flows from alveoli into the deoxygenated blood as the amount of dissolved oxygen in the deoxygenated blood is low and the partial pressure of oxygen in the alveoli is high.
The concentration of carbon dioxide in the deoxygenated blood is very high and the partial pressure of carbon dioxide in the alveoli is low. This causes the flow of carbon dioxide from the blood to the alveoli.

Hence, Henry’s Law holds an important position in the respiration of many organisms.

Factors Affecting Henry’s Law:-

Henry’s Law Constant is dependent upon the following factors.

Nature of gas
Nature of the solvent
Pressure and temperature

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Different gases have different values of Henry’s Law Constant in different kinds of solvents.

This can be explained by Henry’s Law Graph:-

Henry Law Graph

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Limitations of Henry’s law:-

The law holds only when the molecules present in the system are in an equillibrium state.
Henry’s Law is not applicable when the gases are under very high pressure.
This law is also not applicable when the solution and gas take part in a chemical reaction with each other.

At constant pressure, Henry’s Law constant is inversely proportional to the mole fraction of the gas.

It can be represented as follows,

P ∝ X

P = kh . X

Hence, at constant pressure, the equation becomes –

X ∝ 1/kh

The above relation states that, the mole fraction value of gas in liquid increases as Henry’s Law constant decreases.

Temperature increase results in a decrease of solubility of a gas in a liquid. Thus the relation between the solubility of a gas in liquid and temperature can be given as,

T ∝ 1/solubility ---------- (1)

We are familiar with the fact that the increase in Henry’s constant results in a decrease in solubility of a gas in liquid when pressure is kept constant. So the equation can be stated as –

kh ∝ 1/solubility ---------- (2)

From equations (1) and (2),

T ∝ kh

Henry’s Law does not apply to which gas?

The dissolution of molecules of ammonia gas into the water do not follow Henry’s law. The majority of ammonia molecules ( ) unite with water molecules ( ) leading to the formation of i.e. ammonium hydroxide.

further dissociates into and ions.

Thus, the ions present now in the solution are – ions, ions and .

This results in the formation of the following equilibrium state-

Hence, we can conclude that Henrys Law does not hold for NH3 gas as this gas i in water.

Also check-

NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. What is henry’s law/ Define henry law class 12?

The amount of gas absorbed or dissolved in a liquid at

constant temperature is directly proportional to the

pressure exerted by the gas.

2. What are the exceptions of Henry’s Law?

Henry’s Law is only applicable for dilute solutions where the molecular species in the solution and gas is equal.

3. Why is Henry’s Law termed as Limiting law?

Henry’s law cannot be applied to the gases placed under very high pressure.

4. Henry’s Law constant depends on which factor?

Henry’s Law Constant depends on the following factors-

1 . nature of gas

2 . nature of the solvent

3 . pressure and temperature.

5. What is Henry's Law and how is it expressed mathematically?

Henry's Law states that the amount of dissolved gas in a liquid is proportional to the partial pressure of the gas above the liquid. Mathematically, it is expressed as C = kP, where C is the concentration of the dissolved gas, P is the partial pressure of the gas, and k is Henry's law constant.

6. Why is Henry's Law important in everyday life?

Henry's Law is important because it explains many phenomena in our daily lives, such as the formation of bubbles in carbonated drinks when opened, the need for decompression stops in scuba diving to prevent the bends, and the exchange of gases between air and water in our lungs and blood.

7. How does temperature affect the solubility of gases according to Henry's Law?

Temperature inversely affects gas solubility according to Henry's Law. As temperature increases, the solubility of gases generally decreases. This is why warm carbonated drinks go flat faster than cold ones.

8. What is the relationship between pressure and gas solubility in Henry's Law?

According to Henry's Law, there is a direct proportional relationship between pressure and gas solubility. As the pressure of the gas above the liquid increases, the solubility of the gas in the liquid also increases.

9. How does Henry's Law apply to carbonated beverages?

Henry's Law explains why carbonated beverages are pressurized. The high pressure in the sealed container forces more carbon dioxide to dissolve in the liquid. When the container is opened, the pressure decreases, causing the dissolved gas to come out of solution, forming bubbles.

10. What is Henry's Law constant (k) and what does it represent?

Henry's Law constant (k) is a measure of the solubility of a gas in a specific liquid at a given temperature. It represents the ratio of the concentration of the dissolved gas to its partial pressure above the liquid. The value of k is unique for each gas-liquid pair and temperature.

11. How does the nature of the gas affect its solubility according to Henry's Law?

The nature of the gas affects its solubility through the Henry's Law constant (k). Gases with stronger interactions with the solvent (like polar gases in polar solvents) will have higher k values and thus higher solubilities compared to gases with weaker interactions.

12. Can Henry's Law be applied to all gases and liquids?

Henry's Law is most accurate for dilute solutions and gases at moderate pressures. It becomes less accurate for highly soluble gases, very high pressures, or when chemical reactions occur between the gas and the solvent.

13. How does Henry's Law relate to scuba diving and decompression sickness?

Henry's Law explains why divers need to ascend slowly. At greater depths, higher pressure causes more nitrogen to dissolve in the blood. If a diver ascends too quickly, the pressure decreases rapidly, causing the dissolved nitrogen to form bubbles in the blood and tissues, leading to decompression sickness or "the bends."

14. What is the significance of Henry's Law in environmental science?

Henry's Law is crucial in environmental science for understanding gas exchange between the atmosphere and bodies of water. It helps explain phenomena like ocean acidification due to increased atmospheric CO2, and the distribution of pollutants between air and water.

15. How does Henry's Law affect the oxygen content in fish tanks?

Henry's Law governs the dissolution of oxygen in fish tanks. The amount of dissolved oxygen depends on the partial pressure of oxygen in the air above the water. Factors like temperature and salinity can affect the Henry's Law constant, influencing oxygen solubility and thus the well-being of aquatic life.

16. What is the relationship between Henry's Law and Raoult's Law?

While both laws deal with vapor-liquid equilibrium, Henry's Law applies to the solute (usually a gas) in dilute solutions, whereas Raoult's Law applies to the solvent or in ideal solutions. Henry's Law is often used when the solute concentration is low, while Raoult's Law is used for higher concentrations.

17. How does the mole fraction of a gas affect its solubility according to Henry's Law?

Henry's Law states that the mole fraction of the dissolved gas in the liquid is proportional to the partial pressure of the gas above the liquid. As the partial pressure (and thus the mole fraction) of the gas increases, its solubility in the liquid also increases proportionally.

18. Why do fizzy drinks go flat faster in open containers?

Fizzy drinks go flat faster in open containers due to Henry's Law. When the container is open, the partial pressure of CO2 above the liquid decreases. According to Henry's Law, this causes the dissolved CO2 to come out of solution to establish a new equilibrium, resulting in the drink losing its fizz.

19. How does altitude affect the application of Henry's Law?

At higher altitudes, the atmospheric pressure is lower. According to Henry's Law, this lower pressure results in decreased gas solubility in liquids. This is why carbonated drinks might seem fizzier at high altitudes, as the gases come out of solution more readily.

20. What role does Henry's Law play in the human respiratory system?

Henry's Law is crucial in gas exchange in the lungs. The partial pressure difference of oxygen and carbon dioxide between the alveoli and blood allows for efficient gas exchange. Oxygen dissolves into the blood where its partial pressure is lower, while CO2 moves from the blood to the alveoli where its partial pressure is lower.

21. How does Henry's Law relate to the concept of partial pressure?

Henry's Law directly relates the concentration of a dissolved gas to its partial pressure above the liquid. The partial pressure of a gas is its contribution to the total pressure in a mixture of gases. This relationship allows us to calculate the amount of dissolved gas based on its partial pressure in the gas phase.

22. What is the effect of adding salt to water on gas solubility according to Henry's Law?

Adding salt to water generally decreases gas solubility. This is because the salt ions interact with water molecules, reducing the number of water molecules available to dissolve the gas. This effect is known as "salting out" and can be explained by a change in the Henry's Law constant for the gas-solution system.

23. How does Henry's Law apply to the production of champagne?

Henry's Law is crucial in champagne production. During fermentation, CO2 is produced and dissolves in the wine under high pressure. When the bottle is opened, the pressure suddenly drops, causing the rapid release of dissolved CO2, creating the characteristic bubbles and "pop" of champagne.

24. What is the significance of Henry's Law in the context of global warming and ocean acidification?

Henry's Law helps explain the absorption of atmospheric CO2 by oceans. As atmospheric CO2 levels increase due to human activities, more CO2 dissolves in the oceans according to Henry's Law. This leads to ocean acidification, affecting marine ecosystems and the global carbon cycle.

25. How does Henry's Law relate to the concept of vapor pressure?

While Henry's Law deals with the solubility of gases in liquids, vapor pressure relates to the tendency of a liquid to vaporize. Both concepts are related to the equilibrium between a substance in its gas and liquid phases. In some cases, Henry's Law constant can be related to the vapor pressure of the pure substance.

26. Can Henry's Law be applied to mixtures of gases?

Yes, Henry's Law can be applied to mixtures of gases. In this case, each gas in the mixture behaves independently, and its solubility is proportional to its partial pressure in the gas mixture. The total amount of dissolved gases is the sum of the individual gas solubilities.

27. How does the polarity of a solvent affect gas solubility in the context of Henry's Law?

The polarity of a solvent affects the Henry's Law constant (k) for different gases. Polar solvents like water tend to dissolve polar gases more readily than non-polar gases. This is reflected in higher k values for polar gas-polar solvent combinations compared to non-polar gas-polar solvent pairs.

28. What is the relationship between Henry's Law and Dalton's Law of Partial Pressures?

Henry's Law and Dalton's Law of Partial Pressures are often used together in gas solubility calculations. Dalton's Law states that the total pressure of a gas mixture is the sum of the partial pressures of its components. Henry's Law then relates these individual partial pressures to the solubility of each gas in the liquid.

29. How does Henry's Law apply to the storage and transport of gases?

Henry's Law is crucial in the storage and transport of gases. It explains why gases are often stored under high pressure in liquid solvents, as this increases their solubility. When the pressure is released, the gas comes out of solution. This principle is used in various industries, including beverage production and chemical manufacturing.

30. What is the significance of Henry's Law in blood gas analysis?

Henry's Law is fundamental in blood gas analysis. It helps in understanding and calculating the dissolved gas concentrations in blood based on their partial pressures. This is crucial for assessing respiratory function, acid-base balance, and oxygen delivery to tissues in medical settings.

31. How does Henry's Law explain the formation of gas bubbles in liquids?

Henry's Law explains bubble formation when the partial pressure of a dissolved gas exceeds its equilibrium pressure. When pressure decreases or temperature increases, the solubility of the gas decreases. If this causes the dissolved gas concentration to exceed the new equilibrium concentration, bubbles form as the excess gas comes out of solution.

32. What is the role of Henry's Law in the nitrogen cycle?

Henry's Law plays a role in the nitrogen cycle by governing the dissolution of atmospheric nitrogen in water bodies. This dissolved nitrogen can then be used by aquatic organisms or undergo further transformations. The law also affects the release of nitrogen back into the atmosphere from water bodies.

33. How does Henry's Law apply to the concept of supersaturation?

Supersaturation occurs when a solution contains more dissolved solute than is predicted by Henry's Law under the given conditions. This unstable state can occur when conditions change rapidly, such as a sudden decrease in pressure. Supersaturated solutions can lead to rapid bubble formation or crystallization when disturbed.

34. What is the importance of Henry's Law in anaesthesiology?

Henry's Law is crucial in anaesthesiology for understanding the uptake and elimination of inhaled anaesthetics. The law helps predict how changes in the partial pressure of the anaesthetic gas in the lungs affect its concentration in the blood and tissues, allowing for precise control of anaesthesia depth.

35. How does Henry's Law relate to the concept of off-gassing in materials science?

Off-gassing, the release of trapped gases from materials, can be explained by Henry's Law. When the external pressure or temperature changes, the equilibrium between dissolved gases in the material and the surrounding atmosphere shifts, leading to the release of gases. This is important in various fields, from polymer science to space technology.

36. What is the significance of Henry's Law in water treatment processes?

Henry's Law is important in water treatment processes, particularly in aeration and gas stripping. It helps determine the efficiency of removing dissolved gases like hydrogen sulfide or introducing gases like oxygen into water. The law guides the design of treatment systems to achieve optimal gas transfer rates.

37. How does Henry's Law apply to the solubility of oxygen in water at different depths in a lake?

According to Henry's Law, the solubility of oxygen in water increases with depth in a lake due to increased hydrostatic pressure. However, this effect is often counteracted by other factors like temperature decrease and biological activity, which can lead to complex oxygen profiles in deep water bodies.

38. What is the relationship between Henry's Law and the greenhouse effect?

Henry's Law helps explain the exchange of greenhouse gases between the atmosphere and oceans. As atmospheric concentrations of gases like CO2 increase, more dissolves into the oceans according to Henry's Law. This oceanic absorption acts as a buffer against atmospheric increases but leads to ocean acidification.

39. How does Henry's Law affect the design of carbonation systems in the beverage industry?

Henry's Law is fundamental in designing carbonation systems. It dictates the pressure and temperature conditions needed to achieve desired carbonation levels. Manufacturers use this law to determine optimal carbonation pressures, storage conditions, and packaging designs to maintain proper carbonation in beverages.

40. What is the significance of Henry's Law in understanding gas solubility trends across the periodic table?

Henry's Law helps explain gas solubility trends across the periodic table. Generally, gases formed by elements lower in a group have higher solubilities due to increased polarizability. Noble gases, being non-polar, have low solubilities in polar solvents like water, which is reflected in their Henry's Law constants.

41. How does Henry's Law relate to the concept of outgassing in vacuum systems?

Henry's Law is relevant to outgassing in vacuum systems. As the pressure in a vacuum chamber decreases, dissolved gases in materials come out of solution according to Henry's Law. This outgassing can affect the ultimate vacuum achievable and is an important consideration in the design of high-vacuum systems.

42. What is the role of Henry's Law in understanding the behavior of gases in deep-sea environments?

Henry's Law is crucial for understanding gas behavior in deep-sea environments. The high pressures at great depths lead to increased gas solubility in water. This affects the distribution of gases like methane and carbon dioxide, influencing deep-sea ecosystems and geological processes like the formation of gas hydrates.

43. How does Henry's Law apply to the concept of gas chromatography?

In gas chromatography, Henry's Law helps explain the partitioning of analytes between the mobile gas phase and the stationary liquid phase. The distribution of compounds between these phases, governed by their Henry's Law constants, determines their retention times and separation in the chromatographic column.

44. What is the importance of Henry's Law in understanding the formation of clouds and precipitation?

Henry's Law plays a role in cloud formation and precipitation by governing the dissolution of atmospheric gases in water droplets. It affects the equilibrium between water vapor in the air and liquid water in cloud droplets, influencing processes like condensation and evaporation that are crucial to weather patterns.

45. How does Henry's Law relate to the concept of volatile organic compounds (VOCs) in indoor air quality?

Henry's Law helps explain the emission of volatile organic compounds (VOCs) from materials into indoor air. The law governs the equilibrium between VOCs dissolved in materials and their concentration in the air. This is important for understanding and controlling indoor air pollution from sources like paints, carpets, and furniture.

46. What is the significance of Henry's Law in the field of geochemistry?

In geochemistry, Henry's Law is important for understanding gas-water interactions in geological systems. It helps explain phenomena like the formation of mineral deposits from hydrothermal fluids, the behavior of gases in groundwater, and the release of gases from magma during volcanic eruptions.

47. How does Henry's Law apply to the concept of gas solubility in polymers?

Henry's Law describes the solubility of gases in polymers, which is important in fields like packaging and membrane technology. The law helps predict how gases permeate through polymer materials, affecting properties like barrier performance in food packaging or gas separation efficiency in membranes.

48. What is the role of Henry's Law in understanding the behavior of dissolved gases in blood during deep-sea diving?

Henry's Law is crucial for understanding the behavior of dissolved gases in blood during deep-sea diving. It explains why nitrogen dissolves more readily in blood at greater depths (higher pressures) and why divers must ascend slowly to allow this excess dissolved nitrogen to be safely released, preventing decompression sickness.

49. How does Henry's Law relate to the concept of gas evolution reactions in electrochemistry?

In electrochemistry, Henry's Law helps explain the behavior of gases produced during electrolysis. The law governs the solubility of these gases in the electrolyte solution, affecting factors like bubble formation, current efficiency, and the design of electrochemical cells.

50. What is the significance of Henry's Law in the context of air pollution and acid rain?

Henry's Law is important in understanding the transfer of air pollutants like sulfur dioxide and nitrogen oxides from the atmosphere to water droplets in clouds or bodies of water. This process contributes to the formation of acid rain, as these dissolved gases form acidic solutions according to Henry's Law.

51. How does Henry's Law apply to the concept of gas absorption in industrial scrubbers?

Henry's Law is fundamental to the design and operation of industrial gas scrubbers. It determines the efficiency of gas absorption into the scrubbing liquid, helping engineers calculate the necessary liquid flow rates, tower heights, and operating conditions to achieve desired pollutant removal rates.

52. What is the role of Henry's Law in understanding the behavior of dissolved gases in magmatic systems?

In magmatic systems, Henry's Law helps explain the behavior of dissolved gases like CO2 and H2O in magma. It governs the solubility of these gases under different pressure and temperature conditions, influencing processes like magma degassing, volcanic eruptions, and the formation of igneous rocks.