(1)

The first member of the alkyne family is ethyne $\left(C_2{H}_2\right)$, with two carbon atoms bonded by a triple bond. It is a hydrocarbon and the simplest alkyne. Its molecular weight is 26.04 g/mol.

(3)

In homologous series, the two consecutive members will differ by $CH₂$ unit or 14 amu.
The molecular masses of first three members of alkanes with general formula $CₙH₂ₙ₊₂$ are shown below:
Methane $(CH₄)$ = 16 amu
Ethane $(C₂H₆)$= 30 amu
Propane $(C₃H₈)$ = 44 amu
From the above examples, it is clear that atomic mass unit of successive members of a homologous series vary by 14 amu.

(2)

A double covalent bond is formed when two pairs of electrons are shared between them. For example, in an oxygen molecule, there is a double bond between two oxygen atoms as they share two pairs of electrons i.e., 4 electrons.

(2)

A hydrocarbon is an organic chemical compound composed exclusively of hydrogen and carbon atoms. For example, the simplest hydrocarbon is methane molecule with the molecular formula $C{H}_4$

(4)

The bond between two identical non-metallic atoms has a pair of electron equally shared between them. This is due to the equal sharing of electrons between the bonded atoms. Hence, the bonded atoms will hold on the shared pair of electrons.

(1)

Hydrocarbons undergo complete combustion when a sufficient amount of oxygen is available. During the complete combustion of hydrocarbons, carbon dioxide and water are formed.

The equation for the combustion of a hydrocarbon in air can be represented as:

Fuel + Oxygen → Water + Nitrogen + Carbon dioxide

Example:
$C{H}_4 + 2O_2 \to 2H_{2}O + C{O}_2$

(1)

There are four single bonds present in methane as 4 hydrogen atoms satisfy the carbon valency 4 which can be represented as shown in the figure: