Question

A solution was dropped over a slice of potato. It turned blue-black. The solution was

• A. Iodine solution
• B. Metanil solution
• C. Benedict's solution
• D. HCl

Answer 1

The correct option is A

Iodine solution

The correct option is A

The explanation for the correct option:

1. Iodine solution is a potassium iodide and iodine solution in water.
2. It is frequently used as a disinfectant or an antiseptic because it is thought to kill infectious bacteria.
3. It turns the slice of potato blue-black in color because it reacts with the starch present in it.
4. An iodine test can be used to determine the presence of starch.
5. The solution turns dark blue when a few drops of iodine solution are poured onto the starch-containing material.
6. This indicates that starch is present in that substance.

The explanation for the incorrect options:

Option B:

1. The dye Metanil Yellow belongs to the azo family of dyes.
2. Between pH 1.2 and 3.2, it changes color from red to yellow, and thus, it is used as a pH indicator.

Option C:

1. Benedict's solution is a complicated mixture of sodium carbonate, sodium citrate, and copper(II) sulfate pentahydrate that is used as a chemical reagent.
2. It is used to determine the presence of simple carbohydrates such as glucose.
3. Benedict's solution is blue, but it changes color in the presence of simple sugars like glucose.
4. It turns green/yellow if the sugar concentration is minimal, and red if the amount is excessive.

Option D:

1. HCl is an acidic solution.
2. Its pH varies on the basis of the concentration of H⁺ ions in it.

Final Answer: When a solution was dropped over a slice of potato. It turned blue-black. The solution was Iodine solution.