Question

Assertion: the precipitate of zinc chloride is white.
Reason: The chlorides of most of the ions are white
A.Both assertion and reason are correct and reason is the correct explanation for assertion.
B.Both assertion and reason are correct, but reason is not the correct explanation for assertion.
C.Assertion is correct but reason is incorrect
D.Both assertion and reason are incorrect

Answer 1

The colour of an ionic compound is less dependent upon the anions and more dependent upon the cations as they give away electrons. The energy required by a loosely bound electron to escape must be low in order to give a coloured compound.

Complete answer:
Coloured precipitate or coloured compounds can be observed by the presence of free electrons that easily escape the lattice of compound by absorbing the energy available to it from the surroundings. These electrons need very little energy to break through the electrostatic bonds and move from the ground state to an excited state of higher energy.
The higher energy states are incapable of providing enough stability to the electron and they fall back to the ground state energy levels emitting an equal amount of energy that they absorb.
If the absorption is done in the visible spectrum of light then an emission is observed in the same spectrum and we see a colour corresponding to the energy of emission of electrons.
Zinc is a 3-d metal yet it is not part of the transition metals as it does not show the properties similar to that of transition metals. Once such property is the ability to show $d - d$ transitions by the electrons present in the d-orbital of transition metals. But Zinc is the last member and therefore has a fully filled d-orbital due to which it doesn’t show $d - d$ transitions and its salt and complexes remain colorless or white.
Zinc chloride is white in colour but there are many coloured chlorides due to the present of cations that can contribute free electrons (like metals that show $d - d$transitions).
Thus the correct option is (C) as zinc chloride is white but many chlorides are coloured.

Note:
Precipitates are formed when the solubility of the compound in a particular solution becomes too low. It starts settling down or floating (separating out) in its solid form. This is the point where the solution is already saturated with too many ions and therefore the ions of the precipitate recombine to give back the salt.