MCQ
The $pH$ of a ${10^{ - 10}}$ molar $HCl$ solution is approximately
- A$10$
- ✓$7$
- C$1$
- D$14$
✓
Answer
Correct option: B.
$7$
(b) ${10^{ - 10}}M\,\,HCl = {10^{ - 10}}\,M\,[{H^ + }]$. But $pH \ne 10$ because solution is acidic. This is because ${H^ + }$from ${H_2}O({10^{ - 7}}M)$ cannot be neglected.
Total $[{H^ + }] = {10^{ - 7}} + {10^{ - 10}}$
$ = {10^{ - 7}} + (1 + {10^{ - 3}}) = {10^{ - 7}}(1.001)$
That is why $pH = 7$(slightly less than $7$)
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