Question

An excess of potassium ions makes KCl crystals appear violet or Lilac in color since
This question has multiple correct answers
A.Some of the anionic sites are occupied by unpaired electrons.
B.Some of the anionic sites are occupied by a pair of electrons.
C.There are vacancies at some anionic sites.
D.F-centers are created which impart color to the crystals.

Answer 1

Before answering this question, we should know that KCl is potassium chloride which is a metal halide salt, it comprises potassium and chloride. It is crystalline and is white or colorless. It is water-soluble and tastes like salt. It is a naturally occurring mineral.

Complete answer:
Some Cl leaves the lattice sites when KCl is heated in the vapor of K and forms anion vacancies. The K vapor gets combined with the chloride ion to produce potassium chloride. To form k ions, the k atom loses electrons. The electrons that are released get diffused into the crystal to get trapped in the anion vacancy which is known as F-centre. These entrapped electrons gain energy and jump to a higher level when visible light falls on the crystal. When electrons come back to the ground state, energy gets released in the form of light.
So, Option (A) Some of the anionic sites are occupied by unpaired electrons

And Option (D) F-centres are created which impart color to the crystals are correct.

Note:
Uses of KCl are :
In fertilizer – Potassium chloride helps to make fertilizers i.e potash. There are two kinds of potash: Potassium chloride (Muriate of potash, MOP) and Potassium sulphate (Sulphate of potash, SOP).
In Medicine- KCl is used to treat low blood potassium as potassium is a very important element in the human body but it should be taken in a limit because an overdose of it can cause hyperkalemia and can stop the heart and a person can die. It is also used in lethal injections.
In Culinary- It is often mixed with NaCl because of its weak, bitter, unsalty flavor and it can be used as a salt substitute for food. To reduce the bitterness, one could add 1 ppm of thaumatin.
In Industries- For the production of potassium hydroxide and potassium metal.
Other applications include food processing, soaps, scientific applications.