Question

Identify the type of the reaction in the following:
($1$ )$C{H_4} + 2{O_2} \to C{O_2} + 2{H_2}O$
($2$ )$Pb + {O_2} \to Pb{O_2}$

Answer 1

Hint: Methane burns in the presence of oxygen in the first reaction to form oxides of carbon and water. Lead reacts with oxygen to form oxides of lead .In both reactions, oxygen is in its elementary state.

Complete step by step answer:
We have to find the types of reaction of the given reactions.
(1) Given reaction is-
$ \Rightarrow C{H_4} + 2{O_2} \to C{O_2} + 2{H_2}O$
 In this reaction methane reacts with oxygen to form carbon dioxide and water. It is a combustion reaction. Also, here carbon undergoes oxidation as it loses its electrons. Carbon’s oxidation state in methane-
$ \Rightarrow C{H_4} \to x + 4\left( { + 1} \right) = 0$
$ \Rightarrow x = - 4$
But when it forms carbon dioxide then carbon’s oxidation state is-
$ \Rightarrow C{O_2} \to x + 2\left( { - 2} \right) = 0$
$ \Rightarrow x = + 4$
 This is a half-oxidation reaction. Oxygen gas here undergoes reduction by gaining electrons and forming water. In the reaction the oxygen is in its elementary state hence its oxidation state is zero but in water its oxidation state is $ - 2$.This is half reduction. So we can say that this is a Redox reaction.
It is a combustion and Redox reaction.

(2) Given reaction is –
$ \Rightarrow Pb + {O_2} \to Pb{O_2}$
Here lead reacts with oxygen to form lead oxide. Since here two elements combine to form a single substance hence it is a combination reaction. Here lead is in its elementary or free state $Pb$ hence its oxidation state is zero. Oxygen is also in its elementary state hence oxygen also has zero oxidation state. After the reaction, in lead oxide the lead has oxidation state $ + 4$ and oxygen has oxidation state$ - 4$ .Hence here lead undergoes oxidation and oxygen undergoes reduction. So this is a Redox reaction.
It is a combination Redox reaction.

Note:
All the combustion reactions in which elemental oxygen is used and all the other reactions which involve other elements other than oxygen are all Redox reactions because both oxidation and reduction occurs in such types of reactions.