a The pKa of the amino acid glycine is 2.35. What is the Kb ofthe conjugate base

Question

a The pKa of the amino acid glycine is 2.35. What is the Kb ofthe conjugate base of glycine? b What is teh pH of a 1.0M glycine solution? c What is the pH range of a buffered solution composed ofequal molar concentrations of acetic acid and acetate? (Ka= 1.8x 10-5) d what is the pH of a solution composed of 0.40M acetic acidand 0.20M sodium acetate? Thanks!1 a The pKa of the amino acid glycine is 2.35. What is the Kb ofthe conjugate base of glycine? b What is teh pH of a 1.0M glycine solution? c What is the pH range of a buffered solution composed ofequal molar concentrations of acetic acid and acetate? (Ka= 1.8x 10-5) d what is the pH of a solution composed of 0.40M acetic acidand 0.20M sodium acetate? Thanks!1 d what is the pH of a solution composed of 0.40M acetic acidand 0.20M sodium acetate? Thanks!1

Explanation / Answer

We Know that :    pKa + pKb = 14     pKb = 14 - 2.35              =   11.65       Kb = 10-11.65      [ H+ ] = Ka x C                  = 0.0044 x 1.0                  = 0.06683     pH = 1.750      The buffer capacity of the solution is pKa ± 1                                                                                 = 4.744 ± 1       For the buffers the pH can becalculated as :          pH = pKa + log [ salt ] / [ Acid ]                  = 4.744 + log [ 0.20 ] / [ 0.40 ]                   = 4.4429      [ H+ ] = Ka x C                  = 0.0044 x 1.0                  = 0.06683     pH = 1.750      The buffer capacity of the solution is pKa ± 1                                                                                 = 4.744 ± 1       For the buffers the pH can becalculated as :          pH = pKa + log [ salt ] / [ Acid ]                  = 4.744 + log [ 0.20 ] / [ 0.40 ]                   = 4.4429

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