Question

Acid-Base Titration question!?

Explain the difference in change of pH with volume of titrant added near the equivalence point as compared to a point earlier in the titration. (i.e. How does the slope of the titration curve differ at each of these points?)

Answer 1

This is due to strength of acid and bases. Strength of acid and base is given by Ka and Kb

For example consider titration of 1M NaOH titrate against 1M HCl

equilibrium for these acid and bases are

  HCl ------> H+ + Cl-

   Ka = [H] [Cl]/[HCl]

= 1.3 × 10^6

For NaOH

NaOH --------- > Na + + OH-

   Kb= [Na+][OH-]/[NaOH]

High difference between Ka value of acid and base indicate huge difference in hydrogen ion concentration level so after equialence point excess addition of acid or base give huge change in hydrogen ion concentration so that the sharp change in pH value in acid base titration.

for 1M HCl the PH is 3