Determine the pH of an aqueous solution of ammonia if the concentration of the solution is 3(M). `K_(b)`(ammonia)`=1.8xx10^(-5)`.

Explanation

`NH_(3)` is a weak monoacidic base. For such a basic solution, `pOH=(1)/(2)xx10^(-5)`.
As `K_(b)=1.8xx10^(-5)`
`pK_(b)=-log_(10)K_(b)=-log_(10)(1.8xx10^(-5))=4.74`
`therefore`For 3(M) `NH_(3)` solution, `pOH=(1)/(2)pK_(b)-(1)/(2)logc`
`=(1)/(2)xx4.74-(1)/(2)log3=2.13`
`thereforepH` of the solution`=14-pOH=14-2.13=11.87`.