Zinc Sulphide Formula: Definition, Preparation, Properties, Uses

Zinc sulphide is an inorganic compound. The chemical formula is \({\rm{ZnS}}.\) It is the main form of zinc that is found in nature. The naturally occurring mineral of zinc sulphide is called sphalerite (also known as zinc blende). Zinc sulphide exists in two crystalline forms such as sphalerite and wurtzite. Zincblende has a basic structure, consisting of a polar covalent link between the zinc metal and the sulphur atom. Zinc Sulphide Formula is often known as Zincblende or Wurtzite formula.

ZnS is both water-insoluble and denser than water. It occurs naturally as the mineral zinc blende, often known as sphalerite. Sphalerite crystallises as a greyish white substance. It’s a zinc sulphide and iron combination. The burning of a combination of sulphur and zinc can produce ZnS. It comes in a white or yellowish-white crystal form. When zinc sulphate reacts with sodium sulphide or hydrogen sulphide gas is passed through a Zn2+ solution, the insoluble ZnS precipitates. Zinc Sulphide wide range of applications due to its luminous feature.

In this article, we are going to discuss more about Zinc Sulphide, its Definition, Preparation, Properties, Uses, etc. Continue reading to know more.

Zinc Sulphide Chemical Formula

The chemical formula of zinc sulphide is \({\rm{ZnS}}.\) Zinc sulphide contains zinc \(\left( {{\rm{Z}}{{\rm{n}}^{2 + }}} \right)\) and sulphide \(\left( {{{\rm{S}}^{2 – }}} \right)\) ions. The molar mass of zinc sulphide is \(97.474\,{\rm{g}}/{\rm{mol}}.\)

Zinc sulphide appears in two crystalline forms such as sphalerite (zinc blende) and wurtzite. This phenomenon of existing in different forms is called polymorphism. In both forms, the coordinate geometry of zinc and sulphur is tetrahedral. Out of these, the most stable form is sphalerite (zinc blende). Wurtzite is the hexagonal form of zinc sulphide. A rare tetragonal form is called polhemusite.

The two crystalline forms of zinc sulphide can be represented as,

Zinc Sulphide Chemical Formula Derivation

The chemical formula of a compound represents the number of atoms of each element present in one molecule of the compound. The chemical formula of zinc sulphide can be derived using the Criss-cross method.

In the criss-cross method, if we know the valency of each element of a compound, we can easily write its formula. The symbol of the positive part is written to the left-hand side and the symbol of the negative part to its right. The valency of each element is placed as a subscript on the side of the symbol of another element. Subscript \(1\) is not often written. 

Using this, the chemical formula of zinc sulphide is found as,

Zinc sulphide contains zinc \(\left( {{\rm{Z}}{{\rm{n}}^{2 + }}} \right)\) and sulphide \(\left( {{{\rm{S}}^{2 – }}} \right)\) radicals. The valency of zinc radical is two and that of sulphide radical is also two. By criss-crossing the valency numbers, we will get the formula of zinc sulphide as \({\rm{ZnS}}.\)

Preparation of Zinc Sulphide

1. Zinc sulphide is generally produced from the waste materials obtained from the sources such as a smelter, slag, and pickle liquors.

2. Zinc sulphide is also obtained as a by-product during the production of ammonia from methane. That is, during the process, when zinc oxide is used to scavenge the hydrogen sulphide impurities present in natural gas, zinc sulphide is formed. The chemical equation for the reaction is,

\({\rm{ZnO}} + {{\rm{H}}_2}{\rm{S}} \to {\rm{ZnS}} + {{\rm{H}}_2}{\rm{O}}.\)

3. The laboratory preparation of zinc sulphide is done by igniting a mixture of zinc and sulphur. As a result, zinc sulphide is produced. That is,

\({\rm{Zn}}\left( {\rm{s}} \right) + {\rm{S}}\left( {\rm{s}} \right) \to {\rm{ZnS}}\left( {\rm{s}} \right).\)

4. In the presence of sulphide \(\left( {{{\rm{S}}^{2 – }}} \right)\) ions, \({\rm{Z}}{{\rm{n}}^{2 + }}\) salts readily form the precipitate of zinc sulphide \(\left( {{\rm{ZnS}}} \right).\) That is,

\({\rm{Z}}{{\rm{n}}^{2 + }} + {{\rm{S}}^{2 – }} \to {\rm{ZnS}}\)

The above reaction is used as the basis for the gravimetric estimation of zinc.

Properties of Zinc Sulphide (ZnS)

Let us discuss the physical and chemical properties of zinc sulphide.

Physical Properties of Zinc Sulphide (ZnS)

• 1. The pure material of zinc sulphide appears white. The naturally occurring mineral of zinc sulphide appears black due to the presence of impurities in it.
• 2. It is insoluble in water, or it has negligible solubility in water.
• 3. Zinc sulphide has a high melting point, approximately equal to \(2123\,{\rm{K}}.\)
• 4. The density of zinc sulphide is \(4.090\,{\rm{g}}/{\rm{c}}{{\rm{m}}^3}.\)
• 5. Zinc sulphide in a specific activated form (with fewer amounts of certain elements) can exhibit luminescence, fluorescence, and phosphorescence.

Chemical Properties of Zinc Sulphide (ZnS)

The chemical properties of Zinc Sulphide are explained below:

Reaction with Oxygen

Zinc sulphide, when heated with oxygen, zinc oxide and sulphur dioxide are formed. The chemical equation for the reaction can be given as,

\(2\,{\rm{ZnS}} + 3\,{{\rm{O}}_2} \to 2\,{\rm{ZnO}} + 2\,{\rm{S}}{{\rm{O}}_2}\)

Reaction with Hydrochloric Acid

Zinc sulphide, when reacted with dilute hydrochloric acid, gives zinc chloride and hydrogen sulphide. The chemical equation for the reaction can be given as,

\({\rm{ZnS}} + 2\,{\rm{HCl}} \to {\rm{ZnC}}{{\rm{l}}_2} + {{\rm{H}}_2}{\rm{S}}\)

Reaction with Sulphuric Acid

Zinc sulphide reacts with sulphuric acid to give zinc sulphate and hydrogen sulphide. The chemical equation for the reaction can be given as,

\({\rm{ZnS}} + {{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4} \to {\rm{ZnS}}{{\rm{O}}_4} + {{\rm{H}}_2}{\rm{S}}\)

Uses of Zinc Sulphide

The several uses of zinc sulphide include:

1. Zinc sulphide, when activated with a suitable activator, makes it a luminescent material. This property is used in several applications. For example, it is used as a phosphor in cathode ray tubes.
2. The phosphorescent nature of zinc sulphide makes it useful for several decorative and electronic applications.
3. Zinc sulphide can be used as an infrared optical material. That is, it can be used as a plane optical window, or it can be shaped into a lens.
4. Zinc sulphide can be used as a pigment for paints, rubber, and plastics. The common pigment made of zinc sulphide is sachtolith.
5. For low gloss paints, Lithopone, a pigment made of \({\rm{ZnS}}\) and barium sulphate \(\left( {{\rm{BaS}}{{\rm{O}}_4}} \right)\) is used.
6. Powdered zinc sulphide is used as an efficient catalyst. Upon illumination, it produces hydrogen gas from water.
7. The two crystalline forms of zinc sulphide such as sphalerite and wurtzite, are intrinsic, wide-bandgap semiconductors. Zinc sulphide can be doped as either an \({\rm{p}}\)-type semiconductor or an \({\rm{n}}\) -type semiconductor.
8. In nuclear physics, it was used as a scintillation detector by Ernest Rutherford because it emits light upon excitation by \({\rm{X}}\)-rays.
9. It is used as an alternative antimony trioxide in many systems.

Summary

Zinc sulphide is an inorganic compound with the chemical formula \({\rm{ZnS}}{\rm{.}}\) It is also known as zinc blende. Zinc sulphide naturally occurs as sphalerite. It exists mainly in two crystalline forms (polymorphism), such as sphalerite and wurtzite. Sphalerite is the most common polymorph of zinc sulphide. Zinc sulphide is obtained as a by-product from different applications. In the laboratory, it can be prepared by the reaction between zinc and sulphur. The other preparation method, its physical and chemical properties and its common uses are also explained in this article.

FAQs on Zinc Sulphide

We have provided some frequently asked questions here:

Q.1. What is the name of \({\rm{ZnS}}\)?
Ans: The chemical name of \({\rm{ZnS}}\) is zinc sulphide. It is also known as zinc blende.

Q.2. What is the charge on the cation in \({\rm{ZnS}}\)?
Ans: The cation present in zinc sulphide is zinc cation \(\left( {{\rm{Z}}{{\rm{n}}^{2 + }}} \right).\) The charge on it is \( + 2.\)

Q.3. What is zinc sulphide used for?
Ans: Zinc sulphide has got many uses. They include:
1. It is used as a phosphor in cathode ray tubes.
2. It is useful for several decorative and electronic applications.
3. Zinc sulphide can be used as a pigment for paints, rubber and plastics.
4. Zinc sulphide can be used as an infrared optical material.
5. Powdered zinc sulphide is used as an efficient catalyst.

Q.4. Is zinc sulphide phosphorescent?
Ans: Yes, zinc sulphide is a phosphorescent substance. Zinc sulphide, in addition to the suitable activator, exhibits phosphorescence.

Q.5. How do you write the formula of zinc sulphide?
Ans: Zinc sulphide is an inorganic compound. It contains zinc \(\left( {{\rm{Z}}{{\rm{n}}^{2 + }}} \right)\) and sulphide \(\left( {{{\rm{S}}^{2 – }}} \right)\) radicals. The valency of zinc radical is two, and that of sulphide radical is also two. By criss-crossing the valency numbers, we will get the formula of zinc sulphide as \({\rm{ZnS}}{\rm{.}}\)

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