Question

Which of the following is incorrect regarding Henry's law?

• A. Gas reacts with solvent chemically.
• B. Pressure and concentrations are not too high.
• C. Temperature is not too low.
• D. Gas does not change its molecular state in solution i.e., neither dissociates nor associates.

Hint:

Henry's law assumes that the gas does not chemically react with the solvent. If the gas reacts, the law does not apply.

Answer 1

The Correct Option is A

Henry's law states that at a constant temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas above the liquid. The considerations of Henry's law include:

• Gas reacts with solvent chemically: This statement is incorrect regarding Henry's law. Henry's law specifically applies when the gas does not chemically interact with the solvent. If a chemical reaction occurs, the solubility is affected, and Henry's law does not hold.
• Pressure and concentrations are not too high: Henry's law is valid only at low to moderate pressures. At high pressures, deviations occur due to interactions between gas molecules.
• Temperature is not too low: For Henry's law to be applicable, the temperature should not be too low as it can lead to changes in the state of matter, affecting solubility and molecular behavior.
• Gas does not change its molecular state: This condition implies that the gas neither dissociates nor associates in the solution, which is necessary for the proper application of Henry's law.

Therefore, the incorrect statement regarding Henry's law is: Gas reacts with solvent chemically.

Answer 2

According to Henry's law, the amount of gas dissolved in a liquid is directly proportional to the pressure of the gas above the liquid, provided the temperature remains constant. This principle assumes that certain conditions are met:

• The gas does not chemically react with the solvent. This is critical because chemical reactions would lead to changes in concentration unrelated to pressure.
• Both pressure and concentration of the gas are not excessively high, as deviations occur under such conditions due to non-ideal behavior.
• The temperature should not be exceedingly low, as this could lead to changes in solubility unrelated to Henry's law.
• The molecular state of the gas should remain the same within the solution, meaning it neither dissociates into ions nor associates to form larger molecules.

Among the options given, the statement “Gas reacts with solvent chemically.” is incorrect regarding Henry's law. This is because if a gas reacts chemically with the solvent, it does not simply dissolve; rather, a new compound is formed, which violates the fundamental assumption of Henry's law concerning physical solubility only.