Question

Animal skin is X charged and tannin is Y charged. X and Y are respectively

• A. positively, positively
• B. positively, negatively
• C. negatively, negatively
• D. negatively, positively

Hint:

Remember that tanning is essentially a mutual coagulation process.
Since the two substances must have opposite charges to coagulate each other, the options must have different charges (positive/negative or negative/positive).

Answer 1

The Correct Option is B

Step 1: Recall what tanning chemically is.
It's the mutual coagulation of two oppositely charged colloidal systems, the charges neutralise each other and the material hardens.
Step 2: Identify the charge on animal skin.
In the tanning bath, the skin's proteins pick up a positive charge.
Step 3: Identify the charge on tannin.
Tannin's phenolic groups make it behave as a negatively charged colloid.
Step 4: Put it together.
Opposite charges attract and precipitate together, this is exactly what tans the hide.
Final answer: Option 2, X is positively charged, Y is negatively charged.