The other sheet shows titration curves for reaction of a diprotic acid with NaOH

Question

The other sheet shows titration curves for reaction of a diprotic acid with NaOH. On this sheet you need to enter the two Ka values of the acid manually, in cells E1 = 1.00 x 10-3

And E2 = 1.0 0x 10-8.

Enter the volume and concentration data in the pink cells G1, G2 and G4:

            Volume of acid: 100mL:                     Enter 100

            Concentration of acid: 0.040M           Enter 0.040

            Concentration of NaOH: 0.20M         Enter 0.20

What is the pH after 40 mL of NaOH has been added to the diprotic aicd?

Explanation / Answer

pKa data:

pKa1 = 3; pKa2 = 8

for the acid:

mmol acid = MV = 100*0.2 = 20

mmol of base added = 40*0.4 = 16

clearly,

mmol of acid left = 20-16 = 4

mmol of conjguate base  formed = 16

this is a buffer

1st ionization

therefore, we need to apply henderson hasselbach equation

pH = pKa + log(HA-/H2A)

pH = 3 + log(16/4)

pH = 3.602

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.