Question

Which of the following gases at 298 K and 1 atm pressure is having maximum solubility in water?
(A) Methanal, K_H = 0.000018
(B) Argon, K_H = 40.3
(C) Methane, K_H = 0.41
(D) CO₂, K_H = 1.6
Choose the correct answer from the options given below:

• A. Methanal
• B. Argon
• C. Methane
• D. CO₂

Answer 1

The Correct Option is A

To determine which gas has the maximum solubility in water at 298 K and 1 atm pressure, we consider the provided values of Henry's law constant, \( K_H \). Henry's law relates the solubility of a gas in a liquid to the partial pressure of the gas above the liquid, and it is given by:

Solubility \( \propto \frac{1}{K_H} \)

Thus, a lower \( K_H \) value indicates higher solubility. Let's analyze the given options by their \( K_H \) values:

Gas	\( K_H \) (atm)
Methanal	0.000018
Argon	40.3
Methane	0.41
CO2	1.6

Among the options, Methanal has the lowest \( K_H \) value of 0.000018 atm, indicating it has the maximum solubility in water.

Therefore, the correct answer is: Methanal

Answer 2

The solubility of a gas in water is inversely related to its Henry's law constant (KH). According to Henry's Law, the solubility of a gas in a liquid is given by:

\(C = \frac{P}{K_H}\)

Where:

C is the concentration (or solubility) of the gas,

P is the partial pressure of the gas,

K_H is the Henry's law constant.

A lower K_H value indicates greater solubility because it means that the gas is more soluble at a given pressure.

Comparison of the Henry's law constants (K_H):

Methanal: K_H = 0.000018 (lowest K_H, highest solubility)

Argon: K_H = 40.3 (high K_H, low solubility)

Methane: K_H = 0.41 (moderate K_H, moderate solubility)

CO₂: K_H = 1.6 (relatively low K_H, good solubility but not the highest)

Since methanal has the lowest K_H value (0.000018), it has the maximum solubility in water at 298 K and 1 atm pressure.

Thus, the correct answer is Option A: Methanal.