The graph below represents the titration of an amino acid with NaOH solution. Vi

Question

The graph below represents the titration of an amino acid with NaOH solution. View the titration and answer the questions below (parts a through e).

Map Sapling Learning macmillan The graph below represents the titration of an amino acid with NaOH solution. View the titration and answer the questions below (parts a through e (a) At what pH is the average 12 r net charge 12? PK 59.69 Number 2.34 2.00 pH 8 8.01 (b) Where does the amino acid have a net charge of -1? O above pH 9.69 O at pH 9.69 O at pH 6.01 O at pH 2.34 0.5 2.0 O below pH 2.34 OH (equivalents) (c) At what point has enough base been added to react with 1/2 of the NH3 groups? continued below. Number Number Previous Give Up & View Solution Check Answer Next Exit Hint

Explanation / Answer

a)

pH fot net charge in 1/2 --> pKa1 = 2.34

this is the half equivalenc epoint so choose pKA1

b)

the net charge of -1 will be that of --> very high pH

so

NH3+ --> NH2 + H+

COOH --> COO- + H+

so the groups get deprotonated, and COO- charges negatively, then the pH > pKa2

c)

At what point --> this must be between pI and Pka2

so

OH- equivalencts = 1.2 approx

pH = 8.5 approx

d)

best buffering capacity is in th epI

so

pH = 6.01

e)

the isoelectronic poin pI is shown in pH = 6.01

therefore

pI = 6.01

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