Question

TITRATION A TITRATİON B HCL titated with 6NC.l CLİlbal titrated with NA -- Volume of second reagent added (mL Volume of second reagent added (mL) 3.02 41.12 0.0 5.0 10.0 15.0 20.0 21.0 0.0 5.0 10.0 15.0 20.0 21.0 22.0 2.25 52 5 43 23.0 24.0 25.0 2-10 L-35 11.55 11.15 27.0 28.0 29.0 29.0 12.02 2.25 12.33 12.40 2.45 0.0 35.0 40.0 45.0 50.0 12 40.0 2.25 45.0 12.3Y 2.니 ANSWERS TO QUESTIONS 1. Titration A, endpoint pHz 2. pK, or pK,- Titration B, endpoint pH- 4. Why no K asked for Titration A?
any help is greatly appreciated

Answer 1

The end point is the point at which colour chamge occurs in the titration flask. Phenolphthalein is used as indicator. It has pink colour in basic solution and colourless in acidic solution

HIn = H+ + In-

As OH- ions are added dropwise from burette. H+ starts combining with OH - ions and In- becomes free to show its colour.

Thus,

Titration A: the end point pH= 10.5

Titration B: the end point pH= 10.80

2). pKa= PH at equivalent point.

Equivalent point is the point at which H+ ions gets completely reacted with OH- chemically.

A) Equivalent point pH= 2.70

B). Equivalent point pH= 6.35

Pka(A)=2.70

Pka(B)=6.35

3). As pka = - log Ka

Ka= - antilog pKa

A). Ka(A)=-antilog(2.70)=5.01×10^2

B).Ka(B)=-antilog (6.35)=2.23×10^6

4).K is calculated for reactions which does not goes to completion and are in equilibrium. But reaction of strong acid and strong base occurs completely. Since they dissociate completely.