The pH of aqueous solution of ammonia is 11.5. Find molarity of solution. `K_b (NH_4OH)= 1.8 xx 10^(-5)`

Explanation

`pH =11.5, i.e, -log[H^+]=11.5`
`[H^+]=3.162 xx 10^(-12)`
`[OH^(-)]=K_(w)/[H^+]=(10^(-14))/(3.162 xx 10^(-12))=0.0032M`
Let the initial concentration of `NH_(4)OH` be x moles/litre.
`overset(x) (NH_(4)OH) Leftrightarrow overset(0)(NH_(4))+overset(0)(OH^(-))` Initial concentration
`(x-0.0032) " "0.0032" "0.0032`
`K_(b)=(0.0032 xx 0.0032)/(x-0.0032)=1.8 xx 10^(-5) ("given")`
x=0.57M.