Question

Lithopone, a white pigment, is the mixture of:

A) ${\text{ }}BaS{O_4}{\text{ and }}ZnS$

B) ${\text{ }}BaS{\text{ and }}ZnS{O_4}$

C) ${\text{ }}CaS{O_4}{\text{ and }}ZnS$

D) ${\text{ }}CaS{\text{ and }}ZnS{O_4}$

Answer 1

In order to deal with this question first we will define the term lithopone further we discuss its production and according to its reaction we will get the required.

Complete step-by-step answer:

Lithopone, C.I. Pigment White 5, is a combination of inorganic compounds and is commonly used as a white pigment powder. It is made up of a mixture of barium sulfate and zinc sulfide. Such insoluble compounds ideally blend with organic compounds and give opacity. The low cost of production, wider publicity, has made it famous. White pigments are related to titanium dioxide, zinc oxide ('zinc green'), and zinc sulfide.

Co precipitation of barium sulfate and zinc sulfide produces lithopone. The most frequently found co-precipitation is by adding equimolar amounts of zinc sulfate and barium sulfide:

$BaS + ZnS{O_4} \to ZnS.BaS{O_4}$

This route affords a product that is 29.4 wt % $ZnS$ and 70.6 wt % $BaS{O_4}$ . Variations exist, for example, more $ZnS$ -rich materials are produced when zinc chloride is added to the mixture of zinc sulfate and barium sulfide.

Hence, Lithopone, a white pigment, is the mixture of $ZnS$ and $BaS{O_4}$ .

So, the correct answer is option (A).

Note: Barium sulfide is formed by reducing barium sulfate to a carbothermic level. Zinc sulfate is derived by treating sulfuric acid from a number of zinc materials, which are mostly waste. Brilliant white lithopone pigment used in paints, inks, fabrics, paper, linoleum and facial powder. In the 1870s, lithopone was developed as a replacement or supplement for lead carbonate (white lead) to address its toxicity disadvantages, bad weathering and dimness in atmospheres containing sulfur compounds.