Correct option is A
Zinc sulfide is an inorganic compound with the chemical formula of ZnS. This is the main form of zinc found in nature, where it mainly occurs as the mineral sphalerite.
ZnS exists in two main crystalline forms. In each form, the coordination geometry at Zn and S is tetrahedral. The more stable cubic form is known also as zinc blende or sphalerite. The hexagonal form is known as the mineral wurtzite, although it also can be produced synthetically.
Both sphalerite and wurtzite are intrinsic semiconductors. They adopt structures related to many of the other semiconductors, such as gallium arsenide.
Additional Knowledge
Hydrogen sulfide (H2S) is a weak electrolyte. It is partially ionized when in aqueous solution, therefore there exists an equilibrium between un-ionized molecules and constituent ions in an aqueous medium as follows:
H2S ⇌ H+ + HS-
Hydrochloric acid (HCl) is a strong electrolyte, which nearly completely ionizes as
HCl → H+ + Cl-
If HCl is added to the H2S solution, H+ a common ion and creates a common ion effect. The common-ion effect refers to the decrease in solubility of an ionic precipitate by the addition to the solution of a soluble compound with an ion in common with the precipitate. This behavior is a consequence of Le Chatelier's principle for the equilibrium reaction of the ionic association/dissociation. Le Chatelier’s principle can be defined as: If the equilibrium of a system is disturbed by a change in one or more of the determining factors (as temperature, pressure, or concentration) the system tends to adjust itself to a new equilibrium by counteracting as far as possible the effect of the change
Due to the increase in concentration of H+ ions from the added HCl, the equilibrium of the dissociation of H2S shifts to the left. Thus, the dissociation of H2S decreases, the concentration of un-ionized H2S increases, and as a result, the concentration of sulfide ions decreases. Hence, fourth statement is incorrect.
