(3)

Organic compounds have low melting and boiling points because they are made of weak covalent bonds. Thus, the property which is not true regarding organic compounds is that they have high melting and boiling points.

(4)

Carbon as a group 14 element, has four electrons in its outer shell. Carbon typically shares electrons to achieve a complete valence shell, forming bonds with multiple other atoms.

(2)

The electronic configuration of carbon (C) is 2, 4. To complete its octet, it will share its 4 valence electrons with hydrogen atom and form $CH₄$ molecule. As carbon is sharing its 4 valence electrons, it will form four covalent bonds.
Now, the electronic configuration of C in $CH₄$ is 2, 8.
Electronic configuration of Ne (atomic number = 10) is 2, 8. Hence, after the formation of four covalent bonds, carbon attains the electronic configuration of Neon.

(1)

The term isomerism refer to the organic compounds with same molecular formula but different structural formulae. An example is the compound with the molecular formula $C_5{H}_{12}$. It has three isomers: n-pentane, isopentane and neopentane which differ from each other in their structure but they have same molecular formula.

(2)

Since, branching is not possible with carbon 1, 2, 3 so the minimum number of the carbons required by the hydrocarbon to show isomerism is four.

(3)

Structural formula of pentane is:

Number of C - C covalent bonds = 4

Number of C - H covalent bonds = 12

Hence the total number of covalent bonds in the structure of pentane is 16.

(3)

Isomerism is a phenomenon in which two or more compounds have the same chemical formula but possess different structural formulae. Pentane is an organic compound and an alkane with molecular formula $C_5{H}_{12}$. There are five carbons in its structure which can be arranged in three different ways to form 3 different structural isomers of pentane. These are n-pentane, iso-pentane and neo-pentane.

(4)

$C{H}_4, C_2{H}_6, C_3{H}_8$ are all saturated carbon compounds with general formula $C_n{H}_{2n+2}$ whereas $C_4{H}_8$ is an alkene with general formula $C_n{H}_{2n}.$ Thus, $C_4{H}_8$ does not belong to the same homologous series as it is an alkene.

(4)

Homologous series is the series comprising of compounds that share same chemical properties and functional groups. Alkynes have general formula,$C_n{H}_{2n-2}$, where n is number of carbon atoms.

Thus, from the given options, $C_3{H}_4$ belongs to the homologous series of alkynes.

(3)

A homologous series is a family of compounds with the same general formula, same functional group and similar chemical properties. Each family of organic compound is called a homologous series for example,

Homologous series of Alkanes with general formula $C_n{H}_{2n+2}$

Homologous series of Alkene with general formula $C_n{H}_{2n}$

Homologous series of Alkyne with general formula $C_n{H}_{2n-2}$

Hence, from the general formula of the homologous series of alkanes, this can be confirmed that $C_3{H}_8$ belongs to the homologous series of alkanes.