Thank you! The following drawings represent solutions at various stages of the t

Question

Thank you!

The following drawings represent solutions at various stages of the titration of H2A with NaOH. Match the drawings to the points (labeled A through F) on the titration curve. Write your answers as letters in the boxes below the drawings. Two of the drawings will not be used; place an "X" in each of these. Which point(s) during the titration are considered buffer regions? (Circle one or more answers.) A B C D E F Which point represents the second equivalence point? Which point represents pK2? What is the pH at the first equivalence point? (Circle one answer.) pH = pKa1 pH = 14 - pKa1 pH = (pKal + pKa2)/2 pH = pKa1 + pKa2 What is the pH of a 2.0 L sample of 10-0301 M of Potassium Benzoate (C6H5COOK)?

Explanation / Answer

if we name eight boxes as A, B , C , D , E ,F , G , H

then answers for

2- E ( first one for bottom row on left side)

3- F

4- B

5- pH = (pka1 + pka2/) /2

6) 10^ -0.301 = 0.5 M , moles = 0.5x2 = 1

C6H5COO- + H2O <------> C6H5COOH + OH-

pkb = 14-pk(benzoic acid)=14-4.2 = 9.8 , Kb = 10^ -9.8 = 1.585 x10^ -10

Kb = [C6H5COOH][OH-]/[C6H5COO-]

1.585 x10^ -10 = (x/2)^2/( 1-x)/2

x = 1.78 x10^ -5 =OH- moles , [OH-] = 1.78 x10^ -5)/2 = 0.89 x10^-5,

pOH = -log ( 0.89x10^ -5) = 5.05 , pH = 14-5.05 = 8.95

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