Henry’s law calculation at 25°C: if the saturation concentration of oxygen in water is 1.26 mmol/L at a partial pressure of 1 atm, what is the Henry’s law constant H using p = H * C* (report units as atm·L/mmol)?

Introduction:
Henry’s law relates the equilibrium dissolved concentration of a sparingly soluble gas to its partial pressure in the gas phase. Correct unit handling is essential because multiple H conventions exist in the literature. Here, we adopt p = H * C* (pressure proportional to concentration).

Given Data / Assumptions:

• C* (saturation) = 1.26 mmol/L.
• p (oxygen partial pressure) = 1 atm.
• Use p = H * C* and report H in atm·L/mmol.

Concept / Approach:
Rearrange Henry’s law to H = p / C*. Substitute the given values using consistent units. No temperature correction is needed since all data are at 25°C and the law is applied directly.

Step-by-Step Solution:
Write H = p / C*.Insert numbers: H = 1 atm / 1.26 mmol·L^-1.Compute: H ≈ 0.79365 atm·L/mmol.Round sensibly to three significant figures: 0.793 atm·L/mmol.

Verification / Alternative check:
Dimensional check: atm divided by mmol·L^-1 yields atm·L/mmol. The magnitude is consistent with typical oxygen Henry constants at room temperature under this convention.

Why Other Options Are Wrong:

• 0.207 or 0.126 atm·L/mmol: Arise from arithmetic or unit inversion errors.
• 1.26 atm·L/mmol: Numerically equal to C*, not H under p = H * C*.
• 8.74 atm·L/mmol: Off by an order of magnitude; likely unit mix-up.

Common Pitfalls:
Confusing the two common conventions (C* = k_H * p vs p = H * C*); always confirm units before computing.

Final Answer:
0.793 atm·L/mmol