WBJEE · Chemistry · Biomolecules

An electric current is passed through an aqueous solution of a mixture of alanine (isoelectric point 6.0) glutamic acid (3.2) and arginine (10.7) buffered at \(\mathrm{pH}\) 6. What is the fate of the three acids?

A Glutamic acid migrates to anode at \(\mathrm{pH}\) 6. Arginine is present as a cation and migrates to the cathode. Alanine in a dipolar ion remains uniformly distributed in solution.
B Glutamic acid migrates to cathode and others remain uniformly distributed in solution.
C All three remain uniformly distributed in solution.
D All three move to cathode

Verified Solution

Answer & Solution

Correct Answer

(A) Glutamic acid migrates to anode at \(\mathrm{pH}\) 6. Arginine is present as a cation and migrates to the cathode. Alanine in a dipolar ion remains uniformly distributed in solution.

Step-by-step Solution

Detailed explanation

Hints : At \(\mathrm{pH}=6\), glutamic acid exists as a dianionic species & migrates to anode while arginine exists as cationic species & moves to cathode. Alanine does not migrate to any electrode at its isoelectric point .

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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