Question

According to Henry’s Law ‘The partial pressure of the gas in vapour phase (p) is proportional to the mole fraction of the gas in solution.’ The correct statement about Henry’s constant is:
A. Higher the value of $K_H$ at a given pressure, higher is the solubility of the gas.
B. Higher the value of $K_H$ at a given pressure, lower is the solubility of the gas.
C. $K_H$ is not a function of the nature of gas.
D. $K_H$ value for all the gases is the same at a given pressure.

Answer 1

Henry’s law is one of the gas laws that tells us about the contaminants present in air(different types of gases are present in the air which pollute the environment). So, it is an important law that depicts volatilization as a function of contaminant concentration and its partial pressure.

Complete step by step answer:
-Henry’s law states that: at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
-The constant of proportionality of the law is called the Henry’s law constant and it is a constant at a given temperature only.
-Henry’s law can be written in mathematical form as
$p_a=K_H[c]$
Where c=molar concentration of the gas

$p_a$= partial pressure of the gas
$K_H$ =Henry’s law constant
-The Henry’s solubility is also expressed as ratio between aqueous-phase concentration of a species $c_a$ and its gas-phase concentration $c_g$
${{H}^{cc}}={{c}_{a}}/{{c}_{g}}$
-When the temperature is changed, the value of Henry’s law constant also changes.
-The value of Henry’s constant decreases with the increase in solubility.

-Applications of Henry’s law are:
1. Carbonated soft drinks that contain carbon-dioxide which is dissolved at high pressure.
2. Underwater divers need depth dependent oxygen and nitrogen dissolutions as nitrogen tends to dissolve in blood due to higher pressure.
3. Concentrated oxygen in the blood becomes low for climbers or people living at high altitude.
Therefore, the correct answer is Higher the value of $K_H$ at a given pressure, lower is the solubility of the gas.
So, the correct answer is “Option B”.

Note: Henry’s law is applicable only at moderate temperature and pressure. At higher temperature and pressure, the law fails.
Also, if a gas reacts with the liquid, then Henry’s law is not responsible for the solubility of the gas in liquid. Henry’s law does not hold in those circumstances.
Eg, HCl and $N{{H}_{3}}$ react with water. So Henry’s law does not determine the solubility of these gases in water.