Question

a. differentiate between weak and strong (acids and bases) from an equilibrium perspective

b. If your answer in part (a) involves equilibrium, which side (reactants or products) does the equilibrium favor?

c. Briefly explain how each of the following would differentiate between weak and strong acids:

i. Electrical conductivity of equimolar solution of each acid

ii. Equal molarities are each tested with sensitive (+/-1 pH unit) paper

iii. Zinc metal is added to solution of equal concentration

d. Write two equations, one for the dissociation of ammonium hydroxide and the other for the dissociation of sodium hydroxide, that illustrate your answer to part (a).

Answer 1

a.For strong acids and bases, ionisation equilibria are not established, as complete ionisation occurs.

For example, the ionisation of hydrochloric acid does not form an equilibrium:

HCl (g) + H₂O (l) --------------> H₃O⁺ + Cl^-

For weak acids and bases , ionisation equilibrium are established, as only partial ionisation occurs.

For example, the ionisation of acetic acid forms an equilibrium:

CH₃COOH (l) + H₂O (l) ---------------> CH₃COO^- + H₃O⁺

b. In weak acids and bases the equilibrium favor right hand side products.

c. i. Electrical conductivity is more for strong acids and less for weak acids of equimolar solution of each acid.

ii. If pH is more then it is a weak acid and if pH is less then it is a strong acid.

iii. Zn + 2HCl ----------> ZnCl₂ + H₂

Zn + 2CH₃COOH ---------------> Zn(CH₃COO)₂ + H₂

d. NH₄OH ---------> NH₃ + H₂O

NaOH ----------> Na⁺ + OH^-