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A 0.050 M solution of pyruvic acid, an intermediate in metabolism, has a pH of 1

ID: 538518 • Letter: A

Question

A 0.050 M solution of pyruvic acid, an intermediate in metabolism, has a pH of 1.91. Calculate K for pyruvic acid, a weak monoprotic acid. Use significant figures and “E” for scientific notation.
The pH of a 0.50 M solution of ethylamine CHCHNH is 12.17. Calculate the K of ethylamine. Use significant figures and “E” for scientific notation.
A 0.050 M solution of pyruvic acid, an intermediate in metabolism, has a pH of 1.91. Calculate K for pyruvic acid, a weak monoprotic acid. Use significant figures and “E” for scientific notation.
The pH of a 0.50 M solution of ethylamine CHCHNH is 12.17. Calculate the K of ethylamine. Use significant figures and “E” for scientific notation.

The pH of a 0.50 M solution of ethylamine CHCHNH is 12.17. Calculate the K of ethylamine. Use significant figures and “E” for scientific notation.

Explanation / Answer

pH = 1/2 (pKa -logC)

concentration = 0.05 M

1.91 = 1/2(pKa - log(0.05))

pKa = 2.51

Ka = 10^-2.51

    = 3.09*10^-3

pOH = 1/2(pKb-log(c))

pH + pOH = 14

pOH = 14 - 12.17 = 1.83

1.83 =1/2(pKb - log(0.5))

pKb = 3.36

Kb = 10^-3.36

     = 4.36*10^-4