Question

State and explain Henry's law?

Answer 1

Henry’s law lays the relationship between the concentration of a gas in a liquid and the partial pressure of that gas. It also states the other factors on which it depends.

Complete step by step answer:
Henry’s law is actually a gas law that defines that the amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas provided that the temperature is kept constant.
The formula for Henry’s law is:
$P\alpha\; C \\\ P = {K_H}C \\\ P \to Partial\;Pressure\;Of\;Gas\;Above\;Liquid \\\ C \to ConcentrationOfGas \\\ {K_H}\to\; Henry's\;Law\;Constat\;Of\;Gas$
Factors that affect the Henry’s law are:
(a) Nature of the gas
(b) Nature of the solvent
(c) Temperature and pressure
Henry’s law has a number of applications like in a pepsi and carbonated drinks in respiration and even in oxygenation of blood.
Let us understand Henry’s law more in detail with an example of pepsi and carbonated drinks.
What happened in the case of carbonated drinks. The gas above the drink is pure $C{O_2}$ which is kept at the pressure that is slightly above the atmospheric pressure. As a result of Henry’s law, the solubility of $C{O_2}$ is also high in the unopened drink.
Now, when the drink is opened, the $C{O_2}$ escapes into the atmosphere. Due to Henry’s law, as the partial pressure of $C{O_2}$ decreases, solubility of $C{O_2}$in the drink decreases too. This results in dissolved $C{O_2}$ to come out to the surface and escape to the atmosphere. That's why the drink goes flat when opened for long because the concentration of $C{O_2}$ in the drink reaches an equilibrium with the concentration of $C{O_2}$ in the atmosphere.

Note: Limitations of Henry’s law are:
(A) Only applicable when molecules of system are in equilibrium
(B) Does not holds for the gases under high pressure
(C) When the gases react with the solution , Henry’s law does not hold true in this case.
It should be noted that according to Henry’s law the greater the partial pressure of the gas the greater will be its solubility in the liquid.