Question

(a) (i) Differentiate crystalline solids and amorphous solids.
(ii) Explain the rate determining step with an example.

Hint:

A great analogy for the Rate Determining Step is a funnel: No matter how large the top is, the water can only exit as fast as the narrowest part (the neck) allows. Similarly, in an Amorphous solid like glass, the lack of long-range order causes it to flow slightly over decades, which is why very old window panes are often thicker at the bottom!

Answer 1

Concept: Ostwald's dilution law describes the relationship between the dissociation constant (Kₐ) and the degree of dissociation (α) of a weak electrolyte.
Derivation:
Consider a weak acid HA dissociating in water: HA H^+ + A^- Let C be the initial concentration of the acid in mol/L and α be the degree of dissociation. [h] |l|c|c|c| & HA & H^+ & A^-
Initial Concentration & C & 0 & 0
Change due to dissociation & -Cα & +Cα & +Cα
Equilibrium Concentration & C(1-α) & Cα & Cα

The dissociation constant Kₐ is given by: Kₐ = ([H^+][A^-])/([HA]) Substituting the equilibrium concentrations: Kₐ = ((Cα)(Cα))/(C(1-α)) = (C²α²)/(C(1-α)) = (Cα²)/(1-α)
For weak electrolytes, the degree of dissociation α is very small (α 1), so we can approximate 1 - α ≈ 1. Kₐ = Cα² α = √((Kₐ)/(C)) Since concentration C = 1/V (where V is dilution/volume), the expression becomes: α = √(Kₐ · V) This shows that the degree of dissociation is directly proportional to the square root of dilution.