Question

The primary products of hydrocarbon combustion are :
a.) water and carbon
b.) water and carbon monoxide
c.) water and carbon dioxide
d.) hydrogen and carbon monoxide
e.) hydrogen and carbon

Answer 1

Hint: The hydrocarbons are the organic molecules derived from carbon, hydrogen and oxygen majorly. The hydrocarbons are used as fuel which burn to give out the products. The primary products of hydrocarbon combustion are the same as those obtained after burning of methane in sufficient amounts of oxygen.

Complete answer :
Let us begin with what is a combustion reaction.
So, the combustion is an exothermic reaction that involves use of high temperature. This is a redox reaction in which the reductant is the fuel mostly a hydrocarbon and the atmospheric oxygen works as an oxidant giving the gaseous product. The most common example of combustion is the combustion of methane giving carbon dioxide and water. The reaction can be written as -
$C{H_4} \to C{O_2} + {H_2}O$
The hydrocarbons can be defined as the organic compounds which are made up of hydrogen and carbon majorly. The oxygen is also an important constituent of the hydrocarbons. The common hydrocarbons are alkanes, alkenes and alkynes.
The combustion of alkanes is of two types -
Complete combustion and
Incomplete combustion
Complete combustion :-
When the hydrocarbon is heated in presence of sufficient amount of oxygen, then it forms carbon dioxide and water along with heat. This is called complete combustion. The reaction is as-
$C{H_4} \to C{O_2} + {H_2}O + heat$
Incomplete combustion :-
When hydrocarbons burn with less amount of oxygen then the required, then it leads to formation of carbon monoxide and water. This is called incomplete combustion.
$C{H_4} + {O_2}(in{\text{ minimum)}} \to {\text{CO + }}{{\text{H}}_2}O$
When we talk about primary products, we will go with complete combustion only. Thus, carbon dioxide and water will be the primary products.

So, the correct answer is option c.).

Note :
The answer could be water and carbon monoxide if we consider the incomplete combustion but it will not be because in question, we are asked about the primary products after the reaction and the primary products are always considered after the complete reaction only.
$C{H_4} + {O_2}(in{\text{ minimum)}} \to {\text{CO + }}{{\text{H}}_2}O$
The energy required to break the bonds in hydrocarbons is less than the energy released in the formation of bonds in the carbon dioxide and water. Thus, the combustion reaction releases thermal energy which can be directly used or converted into mechanical energy.