(a) In the Solvay process, explain briefly with equations the functions of the following substances: limestone; ammonia. (b) (i) Write a chemical equation f...

Solvay Process and Chemical Reactions

(a) Functions in the Solvay Process:

• Limestone (CaCO3):
  • Function: Source of calcium oxide (CaO) for the regeneration of ammonia.
  • Equation: CaCO3 (g) -> CaO (s) + CO2 (g) (Limestone decomposes to lime and carbon dioxide)
• Ammonia (NH3):
  • Function:
    • Reacts with calcium and chloride ions in brine to form ammonium chloride (NH4Cl).
    • Makes the solution alkaline, favoring the precipitation of calcium carbonate.
  • Equation: Not directly involved in a reaction, but participates in the overall process.

(b) Fermentation and Shattered Bottle:

(i) Glucose Fermentation:

C6H12O6 (aq) -> 2C2H5OH (aq) + 2CO2 (g) (Glucose ferments to ethanol and carbon dioxide)

(ii) Shattered Bottle:

Fresh palm wine undergoes fermentation by yeast. During fermentation, yeast consumes sugar and produces carbon dioxide gas. In a tightly sealed bottle, the CO2 gas gets trapped and builds up pressure. As pressure increases, the glass bottle can no longer withstand the force and shatters.

(c) Metal Reactivity:

(i) Increasing Reactivity: K > Na > Fe > Cu

(ii) Reacting with Cold Water: K, Na (These alkali metals react vigorously with water)

(iii) Colored Salts: Cu (Copper forms characteristic colored salts, like blue copper sulfate)

(d) Redox Reactions and Half Reactions:

(i) Redox Reaction:

A redox reaction is a type of chemical reaction where there is a transfer of electrons between the participating atoms or ions. Oxidation is the loss of electrons, and reduction is the gain of electrons.

(ii) Identifying Redox Reactions:

• Redox: (II), (V)
• Not Redox: (I), (III), (IV)

(iii) Explanation for Redox Reactions:

• (II) AgCl + 2NH3 -> [Ag(NH3)2]Cl:
  • Silver (Ag) loses an electron to become Ag+ (oxidation).
  • Nitrogen (N) in ammonia gains an electron to form the complex ion [Ag(NH3)2]+ (reduction).
• (V) 2FeCl3 + 2KI -> 2FeCl2 + 2KCl + I2:
  • Iron (Fe) in FeCl3 loses an electron to become Fe2+ in FeCl2 (oxidation).
  • Iodine (I) gains an electron to form I2 (reduction).

(iv) Balanced Half Reactions (Examples):

• Oxidation Half Reaction (from reaction II):

                Ag -> Ag+ + e-

• Reduction Half Reaction (from reaction V):

               I- -> I2 + e- (Note: I- needs to be balanced with Cl- from the reactant side)