Question

question 2
12.5 pts
remember that \like dissolves like\ while examining the structure of indigo dye below. which part of this molecule is most attracted to the stationary phase in tlc?
image of indigo dye molecule
the -nh amine groups
indigo dye is not attracted to the stationary phase
the aromatic rings on the ends of the molecule
the double bonded carbon
question 3
12.5 pts
what is the retention factor for a dye that travels 60 mm if the solvent travels 80 mm?
1.33
the retention factor cannot be calculated with the information above
1
0.75

Explanation:

Question 2

In TLC (Thin - Layer Chromatography), the stationary phase is usually polar (e.g., silica gel which is polar). The principle "like dissolves like" means polar parts of the molecule are attracted to the polar stationary phase. The -NH amine groups are polar due to the electronegativity difference between N and H, and the lone pair on N. Aromatic rings are non - polar, the double - bonded carbon is not highly polar, and the statement that indigo dye is not attracted to the stationary phase is incorrect as molecules interact with the stationary phase. So the -NH amine groups are most attracted to the stationary phase.

Step1: Recall the formula for retention factor ($R_f$)

The formula for the retention factor is $R_f=\frac{\text{distance traveled by solute}}{\text{distance traveled by solvent}}$.

Step2: Substitute the given values

The distance traveled by the dye (solute) is 60 mm and the distance traveled by the solvent is 80 mm. So we substitute these values into the formula: $R_f = \frac{60}{80}$.

Step3: Calculate the value

$\frac{60}{80}=0.75$.

Answer:

The -NH amine groups

Question 3