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WHY is it e???? Helppp???!!! :( In the titration of a solution of the extremely

ID: 720763 • Letter: W

Question

WHY is it e???? Helppp???!!! :(


In the titration of a solution of the extremely weak acid, HCN (Ka = 6.2 x 10-10), by a solution of sodium hydroxide of equal concentration, which of the following statements is true?



a. The equivalence point will occur at an acidic pH, and a suitable indicator would be one like alizarin that changes color between pH of 6 and about 7

b. The equivalence point will occur at a neutral pH, and a suitable indicator would be one like bromthymol blue that changes color between pH of 6 and about 7.5

c. The equivalence point will occur at a basic pH, and a suitable indicator would be one like bromthymol blue that changes color between pH of 6 and about 7.5

d. The equivalence point will occur at a basic pH, and a suitable indicator would be one like phenol red that changes color between pH of 7 and about 8

e. The equivalence point will occur at a basic pH, and a suitable indicator would be one like phenolphthalein that changes color between pH of 8 and about 11.

Explanation / Answer

For a titration between a weak acid and a strong base, even the minutest amount of extra base would change the pH drastically to the basic side from 7. So, e is the correct answer.