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 traffic bottleneck: No matter how fast the cars travel on the open highway, the overall speed of the journey is dictated by the slowest section of the road. Similarly, in Amorphous solids, the lack of long-range order allows them to flow extremely slowly over years, which is why window panes in very old buildings are often thicker at the bottom than at the top!

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.