Question

Four gases A,B, C, D have Henry’s law constants 3, 4, 5, 6 respectively. Maximum solubility of the gas in the liquid is found in:
1. It is the same for all
2. B
3. A
4. D

Answer 1

Correct Answer - Option 3 : A

Concept:

• Henry’s Law states that “the partial pressure applied by any gas on a liquid surface is directly proportional to its mole fraction present in a liquid solvent.”
• Henry’s law is given by:

P ∝ C (or) P = kH C

• Where ‘P’ is the partial pressure of the gas, ‘C’ is the concentration of the dissolved gas and ‘kH’ is Henry’s law constant of the gas.

Limitations of Henry’s law: 

• It is applicable when the system is in equilibrium. 
• It is applicable for those gases only which do not react with water (solvent). 
• Gas shouldn’t cause any chemical change in the solution.
• Henry’s law is applicable only when
  •  Pressure is not high
  •  Temperature is not too low
  •  Gas is extremely soluble.

Explanation:

• 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." 
• Henry's constant depends upon the nature of the gas, nature of liquid and temperature.
• As the temperature increases, K_Halso increases.
• At the temperature is constant, the solubility of a gas (S) varies inversely with Henry’s law constant (KH)

\({K_H} = \frac{{Pressure}}{{Solubility\;of\;a\;gas\;in\;a\;liquid}}\;\)

• Thus, the KH value is higher at the given pressure, the lower is the solubility of the gas in the liquid.
• Here, it is given that gases A, B, C, D have Henry’s law constants 3, 4, 5, 6 respectively.
• Gas A has the lowest value of Henry's constant, thus its solubility will be the highest.
• Similarly, Gas D will be the least soluble.

Hence, the maximum solubility of the gas in the liquid is found in gas A.