Question

Assertion (A): Intense weathering of soil shifts its Zero Point Charge towards higher pH owing to greater accumulation of iron and aluminium oxides.
Reason (R): The application of organic matter in soil also pushes the soil Zero Point Charge towards higher pH.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A).
• C. (A) is correct but (R) is not correct.
• D. (A) is not correct but (R) is correct.

Hint:

Zero Point Charge shifts reflect soil chemical changes; organic matter and metal oxides are both influential factors.

Answer 1

The Correct Option is A

Step 1: Fe and Al oxides are variable-charge minerals with a naturally high zero point of charge, around pH 8 to 9.
Step 2: Intense weathering increases their share in the soil, pulling the overall ZPC toward that higher value, supporting A.
Step 3: Organic matter's functional groups interacting with these oxide surfaces are described as reinforcing this same upward shift, supporting R.
Step 4: Both statements hold together, matching the first option.