Fish breathe the dissolved air in water through their gills. Assuming the partial pressures of oxygen and nitrogen in air to be 0.20 atm and

Question

Fish breathe the dissolved air in water through their gills. Assuming the partial pressures of oxygen and nitrogen in air to be 0.20 atm and 0.80 atm, respectively, calculate the mole fractions of oxygen and nitrogen in water at 298 K. Comment on your results

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Trúc Chi 5 years 2021-08-28T20:53:34+00:00 1 Answers 48 views 0

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  1. diemthu
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    2021-08-28T20:55:33+00:00
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    Answer:

    X(O₂) = 0.323

    X(N₂) = 0.677

    Explanation:

    We have the partial pressures of oxygen (O₂) and nitrogen (N₂):

    P(O₂) = 0.20 atm

    P(N₂) = 0.80 atm

    In order to solve the problem, you need the solubilities of each gas in water at 298 K. We can consider 1.3 x 10⁻³ mol/(L atm) for oxygen (O₂) and 6.8 x 10⁻⁴mol/(L atm) for nitrogen (N₂) from the bibliography.

    s(O₂) = 1.3 x 10⁻³ mol/(L atm)

    s(N₂) = 6.8 x 10⁻⁴mol/(L atm)

    So, we calculate the concentration (C) of each gas as the product of its partial pressure (P) and the solubility (s):

    C(O₂) = P(O₂) x s(O₂) = 0.20 atm x 1.3 x 10⁻³ mol/(L atm) = 2.6 x 10⁻⁴mol/L

    C(N₂) = P(N₂) x s(N₂) = 0.80 atm x 6.8 x 10⁻⁴mol/(L atm) = 5.44 x 10⁻⁴ mol/L

    In 1 liter of water, we have the following number of moles (n):

    n(O₂) = 2.6 x 10⁻⁴ mol

    n(N₂) = 5.44 x 10⁻⁴ mol

    Thus, the total number of moles (nt) is calculated as the sum of the number of moles of the gases in the mixture:

    nt = n(O₂) + n(N₂) = 2.6 x 10⁻⁴ mol + 5.44 x 10⁻⁴ mol = 8.04 x 10⁻⁴ mol

    Finally, the mole fraction of each gas is calculated as the ratio between the number of moles of each gas and the total number of moles:

    X(O₂) = n(O₂)/nt = 2.6 x 10⁻⁴ mol/(8.04 x 10⁻⁴ mol) = 0.323

    X(N₂) = n(N₂)/nt = 5.44 x 10⁻⁴ mol/(8.04 x 10⁻⁴ mol) = 0.677

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