Water contains about 42 mg of oxygen per liter at 20°C, and 1 atm. What is Henry's law constant (mol/L atm) for oxygen dissolving in water?

Question

Quizplus · Accepted Answer

Henry's law constant is defined as the ratio of the partial pressure of a gas in the gas phase to its molar concentration in the liquid phase at equilibrium. Using the given information, we can calculate the molar concentration of oxygen in water as follows:

- The molecular weight of oxygen is 32 g/mol
- At 20°C and 1 atm, the solubility of oxygen in water is 42 mg/L, which is 42/1000/32 = 0.00131 mol/L

Now, we can use Henry's law equation to calculate the constant (k) as follows:

p = k*C

where p is the partial pressure of oxygen in the gas phase and C is the molar concentration in the liquid phase. At equilibrium, the partial pressure of oxygen in air is 0.21 atm (since air is 21% oxygen), so we can rearrange the equation as follows:

k = p/C = 0.21 atm / 0.00131 mol/L = 160.3 mol/L*atm

Therefore, the answer is D, which is the closest choice to our calculated value.

Water Contains About 42 Mg of Oxygen Per Liter at 20°C