Does this help? This is the question is written and these are the answers. 1 & 2

Question

Does this help?

This is the question is written and these are the answers.

1 & 2.

3. In the titration of a weak acid with a strong base.

The pH at 10% of the equivalence point volume is approximately pKa-1

and,

The pH at 90% of the equivalence point volume is pKa+1

We will analyze this assumption using a Hendersen-Hasselbalck equation

pH = pKa + log(base/acid)

with,

10% of the equivalence volume,

[Base] = 10

[Acid] = 90

So,

pH = pKa + log(1/9)

      pKa - 0.96

So the pH would be about 1 unit less than pKa, that is, pH = pKa - 1

When, 90% volume of the equivalence volume is placed

[Base] = 90

[acid] = 10

so

pH = pKa + log(90/10)

     = pKa + 0.96

So the pH would be about 1 unit higher than pKa, that is, pH = pKa + 1

What is the minimum pH change required for a sharp indicator color change at the end point? Why? Fraction curve A = equivalent pH. B = amount of math require to neutralized Hel. C = equivalent point.

Explanation / Answer

Yes the way is correct. Our eyes can see the color change when the ratio is around 1: 10 for salt and acid.

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