Henry's law constant for nitrogen at `20^@C` is 76.48 k bar. Assuming the partial pressure as 0.987 bar, calculate mass of nitrogen dissovled in one litre water at `20^@C`.

Explanation

Partial pressure `(p) = K_(H) xx "mole fraction of gas"(X) `
`X = p/(K_H) = (0.987)/(76.480) = 1.29 xx 10^(-5)`
Number of moles (n) of nitrogen in aqueous solution is related to mole fraction (X) as
`X = n/(n + 55.5) = n/(55.5) = 1.29 xx 10^(-5) ` (because n is small, `n + 55.5 = 55.5) `
`n = 1.29 xx 10^(-5) xx 55.5 = 7.16 xx 10^(-4) mol`
Mass of nitrogen dissolved = `n xx GMW = 7.16 xx 10^(-4) xx 28 = 20 xx 10^(-2) g`.