Question

Silver chloride and silver bromide are used in black and white photography.Which of the following are correct in regard to these reactions?

(i) Energy in the form of light is required for the reactions to occur.

(ii) Both the reactions are endothermic.

(iii) Only silver chloride decomposes into solid metal and non - metal gas.

(iv) Both compounds decompose into their respective metal and non - metal gases.

• A. (ii), (iii)
• B. (ii), (iii), (i)
• C. (i), (ii), (iv)
• D. (i), (iv)

Answer 1

The correct option is C

(i), (ii), (iv)

The chemical reactions of silver chloride and silver bromide are as follows:

$2AgCl\left(s\right)\to 2Ag\left(s\right)+C{l}_2\left(g\right)$

$2AgBr\left(s\right)\to 2Ag\left(s\right)+B{r}_2\left(g\right)$

The areas of the photograph exposed to light (energy) becomes black due formation of Ag (Ag is black in colour) and the parts which are not exposed to light are white in colour (AgCl or AgBr are white in colour).

Light is absorbed in this reaction so it is an endothermic reaction. Both compounds decompose into their respective metal (Ag) and non- metal gases ($C{l}_2$, $B{r}_2$).