Question

Which among the following statements is/ are true? Exposure of silver chloride to sunlight for a long duration turn grey due to:
(i) the formation of silver by decomposition of silver chloride
(ii) sublimation of silver chloride
(iii) decomposition of chlorine gas from silver chloride
(iv) oxidation of silver chloride

A. (i) only
B. (i) and (iii)
C. (ii) and (iii)
D. (iv) only

Answer 1

Hint: the reaction used here is the photolytic reaction because it occurs in the presence of sunlight. This type of reaction is also known as photodissociation reaction after reaction silver chloride splits into metal and halogen.

Complete step by step solution:
From your chemistry lessons, you are aware of the decomposition reaction. Decomposition reactions are those reactions in which a compound tends to break in a simpler form.
\[AB\to \,A\,+\,B\]
In most of the decomposition reaction, there is a requirement of electricity, light or energy. A decomposition reaction is also of three types;
(1) Electrolytic decomposition reaction
(2) Thermal decomposition reaction
(3) Photo decomposition reaction
Here we are going to deal with photodecomposition reactions also known as photolysis.
Photo decomposition reactions are those reactions in which the photons present in the sunlight break the reactant molecule into products.
Silver chloride represented as AgCl when exposed to sunlight photolytic reaction takes place which converts sodium chloride into silver(Ag) and halogen(Cl), the sensitivity of silver chloride towards light is very high, that’s why when it comes in contact with sunlight it instantly decompose and form silver metal.
\[\begin{align}
& 2AgCl\to 2A{{g}^{+}}\left( s \right)+\,C{{l}^{-}}\left( g \right) \\
&\
\end{align}\]
Silver chloride is a white colour compound and present in crystalline form. They have very low solubility in water. After exposure to light, the photons from the sunlight decompose silver chloride, a white colour compound, into silver and chlorine signalled by the presence of grey color. After the reaction chlorine gas escapes and grey colour is shown by silver metal.
In this reaction reactant molecules break down into two molecules as a product.
Silver chloride is used as a photographic paper because it reacts with the photons present in the sunlight to form the image through photoreduction.

Thus the correct option will be (A).

Note: Silver chloride always decomposes in presence of sunlight in the form of light energy. When photons are applied on the molecules it breaks down the parent molecule into the resultant molecules.