Identify the decomposition reactions which are endothermic in nature from the following.

a. Respiration

b. Heating of lead nitrate

c. Decomposition of organic matter

d. Electrolysis of acidified water

                                                               (OR)

Explain why Silver chloride when kept in the open turns grey with a balanced chemical equation.

A single reactant decomposes in a decomposition reaction to produce a variety of products. A chemical reaction that results in the breakdown of one reactant into two or more products is known as a decomposition reaction.
A decomposition reaction is generally represented as:

$AB\to A+B$

Where
$AB$ Reactant; $A$ and $B=$Product molecules
The heating of lead nitrate can be represented by the chemical equation given below:

$2PbN{O}_3\to 2PbO+4N{O}_2+O_2$

We can infer from the reaction that leads nitrate breaks down into lead oxide, nitrogen dioxide, and oxygen when heated. Lead oxide, nitrogen dioxide, and oxygen are produced as lead nitrate decomposes.
Electrolysis of acidified water is also an example of an endothermic decomposition reaction.

$2H_{2}O\left(l\right)\to 2H_2\left(g\right)+O_2\left(g\right)$

When acidified water is subjected to an electric current, it breaks down into hydrogen and oxygen gas. As a result, there are twice as many hydrogen molecules produced as oxygen molecules.
Both Respiration and Decomposition of organic matter are exothermic reactions. As a result, options a) and c) are incorrect.

Hence the correct options are b) Heating of lead nitrate and d) Electrolysis of acidified water.

                                                         (OR)

The reaction of silver chloride in the presence of sunlight is as follows:

$2AgCl\to 2Ag+C{l}_2\uparrow$

Because elemental silver, which is grey in color, is produced when silver chloride breaks down, the color of silver chloride changes from white to grey.
It is a type of photolytic decomposition reaction.