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Karnataka Board PUCPUC Science Class 11

On the basis of the equation pH = – log [HX+], 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.

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Question

On the basis of the equation \[\ce{pH}\] = – log \[\ce{[H+]}\], the \[\ce{pH}\] of 10–8 mol dm–3 solution of \[\ce{HCl}\] should be 8. However, it is observed to be less than 7.0. Explain the reason.

Short/Brief Note
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Solution

Here concentration of water cannot be neglected since the solution is very dilute. \[\ce{pH}\] will be less than 7.0. Hence, the total concentration is given as -

\[\ce{[H3O+] = 10^{-8} + 10^{-7}M}\].

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Chapter 7: Equilibrium - Multiple Choice Questions (Type - I) [Page 91]

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NCERT Exemplar Chemistry Exemplar [English] Class 11
Chapter 7 Equilibrium
Multiple Choice Questions (Type - I) | Q 29 | Page 91

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