Partial pressure for methane question

Question

A large, sealed tank contains 1,500 liters of water. When you analyze the air in the top of the tank, you discover that it contains methane at a partial pressure of 0.07 atm. How many grams of methane are dissolved in the water? The K_H for methane at the temperature of the tank is 1.4x10^-3 M / atm.

Answer 1

K_H (Henry's constant) = 1.4x10^-3 M/atm

According to Henry's law, C = KP where P = partial pressure; K = Henry's constant; C = concentration (M)

C = (1.4x10^-3 M/atm)(0.07 atm)

C = 9.8x10^-5 M = 9.8x10^-5 mols/L

mols methane = 9.8x10^-5 mols / L x 1500 L = 0.147 mols

molar mass methane = 16.04 g / mol

grams methane = 0.147 mols x 16.04 g/mol = 2.36 g = 2.4 g methane (2 sig. figs.)