) Use the space below roughly sketch the titration curve you would expect for a

ID: 794076 • Letter: #

Question

) Use the space below roughly sketch the titration curve you would expect for a titration of

a strong acid with a weak base, a weak acid with a strong base, and for a diprotic acid with

a strong base:

2.) A 20.00 mL sample of a diprotic acid H2A was titrated with 0.100 M NaOH. The first

equivalence point was reached after the addition of 14.98 mL of base. The second

equivalence point was reached after the addition of 30.03 mL. Use these two data points to

calculate two values for the molarity of H2A in the original sample. What is the average

experimentally determined Molarity?

3.) The pH after addition of 7.49 mL of 0.100 M NaOH was 3.70, and the pH after the

addition of 22.52 mL NaOH was 7.10.

Use these data points to calculate Ka1 and Ka2 for H2A.

4.) The initial pH of the sample (before NaOH addition) was 1.91. Use this value to calculate

Ka1. Does this agree with Ka1 calculated above using V1/2?

Please show steps and give reason. thanks.

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At first point,

2*C1V1= C2*V2

20*M*2=0.1*14.98

M=(0.1*14.98)/40=0.03745

At second point,

2*C1V1= C2*V2

20*M*2=0.1*30.03

M=(0.1*30.03)/40=0.075075

Average molarity=(0.075075+0.03745)=0.112525

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Ka=[H+][HA-]/[H2A]

pKa=pH - log[HA-]/[H2A]

As, acid is weak, [HA-]=[NaOH]=0.1*7.49/27.49=0.027

[H2A]=(20*0.1125/27.49) - 0.027=0.5484

pKa=3.7- log(0.27/0.5484)

Ka=9.8 * 10^-6

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