Question:
Based on the equation pH = – log [H+], the pH of 10-8 mol dm-3 solution of HCl should be 8. However, it is observed to be less than 7.0. Explain the reason.
Solution:
The solution is very dilute here and we know that HCl reacts with water to form hydronium ion. A decrease in pH can be observed as a result of a large concentration of
H+. Hydronium ion concentration also to be considered here.
Now total pH will be; [H3O+] = 10-8 + 10-7 M = 7
Hence the solution will be acidic.
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