The changes which take place when fats and oils are oxidised:

The following diagram displays a chemical reaction. Observe it carefully and answer the following questions:
$(a)$ Identify the type of chemical reaction that will take place and define it. How will the colour of the salt change?
$(b)$ Write the chemical equation of the reaction that takes place.
$(c)$ Mention one commercial use of this salt.

$(a)$ Give an example of a combination reaction which is exothermic.
$(b)$ Identify the oxidizing agent and reducing agent in the following reaction:
$H_{2}S + Cl_{2} \rightarrow 2HCl + S$
$(c)$ Name the phenomenon due to which the taste and smell of oily food changes when kept for a long time in the open. Suggest one method to prevent it.

State whether the following statement is true or false:
On heating lead nitrate crystals, the emission of brown fumes occurs.

The following reaction is an example of a:
$4 NH_{3}(g) + 5 O_{2}(g) \longrightarrow 4 NO(g) + 6 H_{2}O(g)$
$(i)$ displacement reaction
$(ii)$ combination reaction
$(iii)$ redox reaction
$(iv)$ neutralisation reaction

Write true or false for the following statement:
The reaction $Zn(s) + CuSO_4(aq) \longrightarrow ZnSO_4(aq) + Cu(s)$ is an example of a double displacement reaction.