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Question: Answered & Verified by Expert
0.1MNaOH is titrated with 0.1 M, 20 ml HA till the end point, K a HA = 6×10 6 and degree of dissociation of HA is small as compared to unity. What is the pH of the resulting solution at the end point?
ChemistryIonic EquilibriumJEE Main
Options:
  • A 6.23
  • B 9.22
  • C 7.21
  • D 8.95
Solution:
1552 Upvotes Verified Answer
The correct answer is: 8.95
NaOH2+HA2NaA+H2O 
At end point 0.1×20=2
  20 mLNaOH is required for the complete neutralization of HA
NaA is a salt of strong base and weak acid
Thus, will undergo hydrolysis and solution will becomes basic
C= NaA = 2 20+20 =0.05 M
And pK a =log 6× 10 6 =5.2
pH at the end point =7+ 1 2 pK a +logC
7+ 1 2 5.2+log0.05 =8.95

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