Question

1. Gas (A) is more soluble in water than the gas (B) at the same temperature. Which one of the two gases will have the higher value of ${K_H}$ (Henry’s constant) and why?
2. In a non-ideal solution, what type of deviation shows the formation of maximum boiling azeotropes?

Answer 1

1. Hint:Solubility of a gas in a liquid is dependent on temperature and partial pressure. Higher is the value of ${K_H}$(Henry’s constant) lower is the solubility of gas in the liquid.

Complete answer:
Henry's law states that the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid when the temperature is kept constant. It Is denoted by ${K_H}$, Henry’s Constant.
$P = {K_H}C$
Where
P is the partial pressure of the gas
${K_H}$ is the henry law constant
C is the temperature
The rate constant ${K_H}$ is dependent on various factors like nature of the gas, nature of the solvent and the temperature and pressure of the gas. All these factors are variables depending upon the type of gas. Therefore the Henry’s law constant is different for every gas.
Therefore in the aforesaid question the gas (A) is more soluble than the gas (B) which means it has a lower value of ${K_H}$ than the other gas. Therefore the gas (B) which has lower solubility will have higher ${K_H}$ value.

Note:
This law is only applicable when the molecules of the system are in a state of equilibrium. The law does not hold true when gases are placed under extremely high pressure.


2. Hint:The azeotropes boiling point is different from its constituent’s boiling point. Maximum boiling azeotropes is formed by the negative deviation from Raoult's Law.

Complete answer:
Azeotropes are defined as those liquid mixtures whose composition in liquid and vapour phase remains the same. Each azeotrope has a characteristic boiling point. The azeotropes have two types of deviations. If the boiling point of an azeotrope is less than the boiling point temperatures of any of its constituents it is known as a positive azeotrope, or if greater than the boiling point of any of its constituents it is called a negative azeotrope.
Raoult's law states that the partial pressure of each component of an ideal mixture of liquids is equal to the vapour pressure of the pure component multiplied by its mole fraction in the mixture. In a non-ideal solution Raoult's law is adapted by incorporating two factors that account for the interactions between molecules of different substances. The deviations from the ideal gas-law called as the fugacity coefficient and The the activity coefficient is a correction for interactions in the liquid phase between the different molecules helps us to determine the deviation in the non-ideal gas. If the vapor pressure of a mixture is lower than expected from Raoult's law, there is said to be a negative deviation. If the vapor pressure is greater than expected from Raoult's law, it shows positive deviation.

In a maximum boiling azeotrope, the liquid mixture has a higher boiling point than the individual parts. It occurs due to negative deviation. A solution that shows large negative deviation from Raoult's law forms a maximum boiling azeotrope at a specific composition.

Note:
Azeotropes can form only when a mixture deviates from Raoult's Law. The Raoult’s Law is applicable on non-ideal gas and where an ideal solution is formed. Ideal solution means where equal amounts of solute and solvent are present in a mixture.