Question

Pearl white is:

{A:AsOCl} \\\ {B:SbOCl} \\\ {C:BiOCl} \\\ {D:{{\left( {N{H_4}} \right)}_2}C{O_3}} \end{array}$$

Answer 1

As the name suggests, pearl white refers to any of the several i.e. either white or pearly white materials or substances possessing iridescent or optical characteristics like nacre. So in this question, we have to find out which of the given compounds exhibit pearlescent properties.

Complete step by step answer:
Among different compounds given in the options, arsenic monoxide monochloride ($AsOCl$), antimony oxychloride ($SbOCl$) and ammonium carbonate (${\left( {N{H_4}} \right)_2}C{O_3}$) occur as white powder but do not exhibit pearlescent properties. The structure of these compounds are depicted below:

The compound given in option C i.e. Bismuth oxychloride ($BiOCl$) is a lustrous white solid that pearlescent properties and thus, also known as pearl white. Light wave interference from the plate-like structure of bismuth oxychloride i.e.$BiOCl$ contributes to its pearly iridescent light reflectivity (basically optical properties) as that of nacre.

The structure of$BiOCl$contains layers of $C{l^ - }$, $B{i^{3 + }}$and ${O^{2 - }}$ ions which are ordered in the form of $Cl - Bi - O - Bi - Cl - Cl - Bi - O - Bi - Cl$, i.e., having alternating anions and cations. Actually this type of layered structure contributes to the pearlescent characteristics of properties of Bismuth oxychloride.

Hence, the correct answer is Option C.

Note: Pearl white or bismuth oxychloride is widely employed in cosmetics. It is actually a constituent of the pearly pigment that is usually present in the eye shadows, powders, hair sprays, nail paint, or other cosmetics. In cosmetics, Bismuth oxychloride is known by the name C.I. 77163. The analogous compound of bismuth oxychloride i.e. bismuth oxynitrate is also widely used as a white pigment.