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pH of weak acid + strong acid is considered one the most difficult concept.
17 Questions around this concept.
Which one of the following statements is not true?
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R:
Assertion A: pKa value of phenol is 10.0 while that of ethanol is 15.9
Reason R : Ethanol is stronger acid than phenol.
In the light of the above statements, choose the correct answer from the options given below:
The value of the degree of dissociation for a weak electrolyte is decreased by the addition of a strong electrolyte having a common ion. As a result of this effect, the concentration of the uncommon ion of the weak electrolyte decreases.
For example:
Applications of Common ion effect
Isohydric Solution: These are the solutions having the same concentration of common ions.
The pH of a mixture of a weak acid and a strong acid can be understood using the following example.
Weak acid: H2S (0.1M)
Strong acid: HCl (0.3M)
The Ka value for this mixture = 1.2 x 10-20
The chemical equation for H2S is given as follows:
Initial: c 0 0
Equil: c - c? c? c?
Thus, the equilibrium constant Ka is given as follows:
Again, the chemical equation for HCl is given as follows:
Initial: 0.3 0 0
Equil: 0 0.3 0.3
Thus, total [H+] for the mixture = c? + 0.3
[H+] = 3 x 10-1 (? is very small for weak acids)
Now, the pH for the mixture is given as follows:
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