Final answer:
To calculate the molar concentration of O₂ in the surface water of a mountain lake, we can use Henry's law. We are given the partial pressure of O₂ in air at sea level (0.21 atm), the solubility of O₂ in water at 20⁰C and 1 atm pressure (1.38×10⁻³ M), and the atmospheric pressure at the mountain lake (675 torr). Using the Henry's law equation C = k * P, we can calculate the molar concentration of O₂ in the surface water to be 2.898×10⁻⁴ M.
Step-by-step explanation:
To calculate the molar concentration of O₂ in the surface water of a mountain lake, we can use Henry's law. Henry's law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. The equation relating the concentration of a gas in a solution to its partial pressure is given by: C = k * P, where C is the molar concentration of the gas, k is the Henry's law constant, and P is the partial pressure of the gas. In this case, we are given the partial pressure of O₂ in air at sea level (0.21 atm), the solubility of O₂ in water at 20⁰C and 1 atm pressure (1.38×10⁻³ M), and the atmospheric pressure at the mountain lake (675 torr). We can convert the atmospheric pressure from torr to atm by dividing by 760, so 675 torr is equal to 0.887 atm. We can now use the Henry's law equation to calculate the molar concentration of O₂ in the surface water:
C = k * P = (1.38×10⁻³ M/atm) * (0.21 atm) = 2.898×10⁻⁴ M