Question

The pHpH of a solution is 5.00. To this solution, sufficient acid is added to lower the pHpH to 2.00. The corresponding increase in H3O+H3O+ ion concentration is

Answer 1

Dear Student,

At pH = 5.0 , the H⁺ ion concentration = 10^-5 M or 10^-5 mol / L

Now, to make the pH = 2.0, the H⁺ ion concnetration will be = 10^-2 mol / L


So, to make the solution the H₃O⁺ extra added to the solution will be =
$$\begin{gathered} M_1{V}_1+M_2{V}_2=M_3{V}_3 \\ Letthesimilaramountofacidequalto1Lisaddedtothesolutionofpreviousacid \\ {10}^{-5}\times 1+M\times 1={10}^{-2}\times 2 \\ M=2\times {10}^{-2}-{10}^{-5} \\ ={10}^{-2}(2-{10}^{-3}) \\ ={10}^{-2}\times 1.999 \\ \approx 2\times {10}^{-2}M \end{gathered}$$
So, the H⁺ ion concentration will be 2 x 10-2

Regards