Question

Match List I with List II
List I (Weathering Reaction):
A. $\text{CaSO}_4 + 2\text{H}_2\text{O} \rightarrow \text{CaSO}_4 \cdot 2\text{H}_2\text{O}$
B. $2\text{Fe}_2\text{O}_3 \rightarrow 4\text{FeO} + \text{O}_2$
C. $\text{KAlSi}_3\text{O}_8 + \text{HOH} \rightarrow \text{HAlSi}_3\text{O}_8 + \text{KOH}$
D. $4\text{FeO} + \text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3$

List II (Weathering process):
I. Oxidation
II. Hydration
III. Reduction
IV. Hydrolysis

Choose the correct answer from the options given below:

• A. A - II, B - III, C - I, D - IV
• B. A - II, B - III, C - IV, D - I
• C. A - III, B - II, C - I, D - IV
• D. A - III, B - IV, C - I, D - II

Hint:

To easily identify weathering reactions:
Addition of water molecule $\rightarrow$ Hydration.
Reaction involving ionic split of water ($H^+$ replacement) $\rightarrow$ Hydrolysis.
Gain of oxygen electron loss $\rightarrow$ Oxidation.
Loss of oxygen electron gain $\rightarrow$ Reduction.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Chemical weathering involves the alteration of the chemical and mineralogical composition of rocks and minerals through chemical reactions with water, oxygen, and acids.
These reactions transform primary minerals into secondary minerals and soluble ions.

Step 2: Detailed Explanation:
Let us match each chemical weathering reaction in List I with its corresponding process in List II:
1. Reaction A: $\text{CaSO}_4 + 2\text{H}_2\text{O} \rightarrow \text{CaSO}_4 \cdot 2\text{H}_2\text{O}$
In this reaction, water molecules are chemically combined with anhydrous calcium sulfate (anhydrite) to form hydrous calcium sulfate (gypsum).
This process is called Hydration (II). Thus, A matches with II.
2. Reaction B: $2\text{Fe}_2\text{O}_3 \rightarrow 4\text{FeO} + \text{O}_2$ (often occurring under anaerobic or waterlogged conditions).
Here, ferric iron ($\text{Fe}^{3+}$ in hematite) is converted to ferrous iron ($\text{Fe}^{2+}$ in wustite) through the loss of oxygen, representing a chemical Reduction (III). Thus, B matches with III.
3. Reaction C: $\text{KAlSi}_3\text{O}_8 + \text{HOH} \rightarrow \text{HAlSi}_3\text{O}_8 + \text{KOH}$
This reaction involves water splitting into $\text{H}^+$ and $\text{OH}^-$ ions, where the hydrogen ion replaces potassium in the feldspar lattice.
This chemical decomposition by water is called Hydrolysis (IV). Thus, C matches with IV.
4. Reaction D: $4\text{FeO} + \text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3$
In this reaction, oxygen combines with ferrous iron ($\text{Fe}^{2+}$) to form ferric iron ($\text{Fe}^{3+}$), which is a classic chemical Oxidation (I). Thus, D matches with I.
This gives the match: A - II, B - III, C - IV, D - I.

Step 3: Final Answer:
The correct matching sequence is A - II, B - III, C - IV, D - I, which corresponds to Option (B).