From the figure of column chromatography given below, identify incorrect statements.
A. Compound 'c' is more polar than 'a' and 'b'
B. Compound 'a' is least polar
C. Compound 'b' comes out of the column before 'c' and after 'a'
D. Compound 'a' spends more time in the column
Choose the correct answer from the options given below:

Solution

Chemistry ma’am · 3 steps

The band that has travelled farthest down is the least polar one, and it leaves the column first.

1. How the column separates. The adsorbent (silica gel or alumina) is polar. A more polar compound is held more strongly, so it moves down slowly. A less polar compound is held weakly and is carried down quickly by the eluent.
2. Read the figure. Band 'c' is lowest, so it has moved the most and is the least polar. Band 'a' is at the top, so it is held most strongly and is the most polar. Polarity order: a > b > c. Elution order: c first, then b, then a.

   Statement	What the figure says	Verdict
   A. 'c' is more polar than 'a' and 'b'	'c' moved farthest, so it is the least polar	incorrect
   B. 'a' is least polar	'a' moved least, so it is the most polar	incorrect
   C. 'b' comes out before 'c' and after 'a'	'b' comes out after 'c' and before 'a'	incorrect
   D. 'a' spends more time in the column	'a' is held most strongly, so it elutes last	correct

3. So. Statements A, B and C are incorrect, and only D is correct. The answer is (d).

The idea to keep. On a polar adsorbent, more polar means held tighter and moves slower. The lowest band is the least polar and is eluted first. The top band stays longest.

Answer from the NTA final answer key. Solution by PrepWiser.