Question

Which of the following have lithopone as their mixture?

$${\text{A}}{\text{. ZnC}}{{\text{O}}_3},{\text{BaC}}{{\text{O}}_3} \\\ {\text{B}}{\text{. ZnS}},{\text{N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4} \\\ {\text{C}}{\text{. ZnS}}{{\text{O}}_4},{\text{BaS}}{{\text{O}}_4} \\\ {\text{D}}{\text{. ZnS}},{\text{BaS}}{{\text{O}}_4} \\\$$

Answer 1

Hint- Here, we will proceed by discussing the pigment lithopone. Then, we will write down the various constituents from which it is made up. We will also show the chemical reaction corresponding to the formation of lithopone.

Complete step-by-step answer:
Lithopone is basically a white colored pigment and is a mixture of inorganic compounds that is commonly used as white pigment powder. This is made up of a mixture of barium sulfate (${\text{BaS}}{{\text{O}}_4}$) and zinc sulphide (${\text{ZnS}}$). Such insoluble compounds ideally blend with organic compounds and give opacity. The low cost of production, wider visibility, has made it famous.
While barium sulfate (${\text{BaS}}{{\text{O}}_4}$) is almost fully inert, zinc sulfide (ZnS) degrades when exposed to UV light, which causes the pigment to darken. The magnitude of this UV reaction depends on a combination of two factors which includes how much zinc sulfide (ZnS) is the composition of the pigments, and the overall cumulative UV exposure of the pigment.
When barium sulphide (${\text{BaS}}$) is mixed with zinc sulfate (${\text{ZnS}}{{\text{O}}_4}$) we will get the pigment lithopone (${\text{ZnS}}{\text{.BaS}}{{\text{O}}_4}$). The chemical reaction corresponding to this is shown below
${\text{BaS}} + {\text{ZnS}}{{\text{O}}_4} \to {\text{ZnS}}{\text{.BaS}}{{\text{O}}_4}$
Usually, in lithopone, there is 70.6 % ${\text{BaS}}{{\text{O}}_4}$ and 29.4 % ZnS as the constituents of the mixture.
Therefore, ${\text{ZnS}},{\text{BaS}}{{\text{O}}_4}$ have lithopone as their mixture.
Hence, option D is correct.

Note- Because lithopone is highly insoluble, lithopone is usually non-toxic. Lithopone is used as a radiocontrast agent in the medicines. Lithopone is also used in plastic and coating systems as a substitute for titanium dioxide. Also, there are two grades of lithopone named gold seal and bronze seal.