Gen Chem, Factors Affecting Solubility

[coffeecat91]

Homework Statement

Calculate the mass of nitrogen dissolved at room temperature in an 80.0L home aquarium. Assume a total pressure of 1.0 atm and a mole fraction for nitrogen of .78.

Homework Equations

Mole fraction= moles solute/moles solution

S_gas=K_H x P_gas

K_H = 6.1 x 10^-4 M/atm

The Attempt at a Solution

S_gas = (6.1 x 10^-4)(1 atm)
S_gas = 6.1 x 10^-4
6.1 x 10^-4/ 1 L x 80.0 L = 4.88 x 10^-2 moles
(4.88 x 10^-2 moles) x 28.02 g N_s/ 1 mol = 1.37 g N₂

the correct answer is 1.1 g N₂
Where did I go wrong and where does the mole fraction bit come into play? Thanks!

 

[Borek]

Where did I go wrong and where does the mole fraction bit come into play?

Partial pressure.