The concentration of an aqueous solution of ammonia is 0.01(M). What is the pH of the solution? If 0.001 mol of `NH_4Cl` is added to 100 mL of that solution, state whether the pH of the solution will increase or decrease. Mention the change in the value of pH. `[pK_b(NH_3)=4.74]`

Explanation

pH of an aqueous solution increases when `OH^-` ions are added to the solution. Since pH of the solution=3
`[H_3O^+]=10^(-pH)=10^(-3)(M)` if the pH of the solution
=3.4 then `[H_3O^+]=10^(-pH)`
`=10^(-3.4)(M)=3.98xx10^(-4)(M)`
Hence, pH of the solution will increase from 3.0 to 3.4 when molar concentration of `H_3O^+` ions in the solution`=(10^(-3)-3.98xx10^(-4))=6.02xx10^(-4)(M)`
Therefore, `6.02xx10^(-4)` mole of `OH^-` ions are to be added to 1L HCl solution in order to increase the pH of the solution from 3.0 to 3.4