Introduction:
Henry's law states that the amount of gas dissolved in a liquid is proportional to the partial pressure of the gas above the liquid. Henry's constant for a gas in a particular solvent is the proportionality constant. In this question, we have to determine the molal concentration of argon in water when it is stored above water at 10 bar pressure given that Henry's constant for argon is 40K bar in water.

Formula:
The molal concentration of a gas in a solvent can be calculated using the following formula:

molality (m) = (pressure of gas above the solution) x (Henry's constant) / (RT)

where R is the gas constant and T is the temperature.

Solution:
Given,
pressure of argon above water solution = 10 bar
Henry's constant for argon in water = 40 K bar

We know that the temperature is not given in the question, but we can assume that it is constant. Therefore, we can use the formula to calculate the molality of argon in water as follows:

m = (10 bar) x (40 K bar) / (0.0821 atm L/mol K x T)

We can simplify the equation as follows:

m = (400 bar K) / (0.0821 atm L/mol K x T)

Since the temperature is not given, we cannot calculate the exact molality of argon in water. However, we can say that the molality is directly proportional to the pressure of the gas above the solution, and inversely proportional to the temperature.

Conclusion:
In conclusion, we can determine the molal concentration of argon in water when it is stored above water at 10 bar pressure given that Henry's constant for argon is 40K bar in water. The molal concentration can be calculated using the formula m = (pressure of gas above the solution) x (Henry's constant) / (RT), where R is the gas constant and T is the temperature. Since the temperature is not given, we cannot calculate the exact molality of argon in water.

M = K×P.