Answer: Option D. -> C4H8
:
D
The homologous series given here is the alkene series. In a homologous series, every successive member differs by ${\text{CH}}_2$ group. So, the successive member after${\text{C}}_3{\text{H}}_6$ in the given alkene homologous series is${\text{C}}_4{\text{H}}_8$.

Answer: Option B. -> allotropy
:
B
Allotropy is the property of some chemical elements to exist in two or more different forms in the same physical state.
Allotropes are the different structural modifications of an element, i.e., atoms are bonded together in different manner or arrangement.

Answer: Option C. -> aldehyde
:
C
The given compound has the formula ${\text{CH}}_3{\text{CH}}_2\text{CHO}$. As it has a -CHO group at terminal position, its IUPAC nomenclature is propanal. The functional group -CHO represents an aldehyde.

Answer: Option B. -> Both statements are correct and statement 2 is the correct explanation for statement 1.
:
B
Carbon cannot donate or accept electrons to obtain noble gas configuration as ${\text{C}}^{4-}$ and ${\text{C}}^{4+}$ are unstable in nature.
$C^{4-}$ is unstable because it would be difficult for the nucleus with six protons to hold on to ten electrons.
${\text{C}}^{4+}$ is unstable because it would require an excessively large amount of energy to remove four electrons.
Since both ${\text{C}}^{4-}$ and ${\text{C}}^{4+}$ ions are unstable in nature, carbon overcomes this problem by sharing its valence electrons with other atoms to obtain the nearest noble gas electronic configuration.
Hence, the given statements are correct and statement 2 is correctly explainingstatement 1.

Answer: Option D. -> ketone
:
D
The given compound is propanone having the formula ${\mathrm{CH}}_3{\mathrm{COCH}}_3$. The functional group present in this compound is ketone as it has $\text{C=O}$ group present in between two alkyl groups.

Answer: Option A. -> -OH
:
A
The IUPAC name of the given molecule,has '-ol' as its suffix.
'-ol' is the suffixforalcohols. Hence,the functional group of an alcohol is -OH.

Answer: Option C. -> Methanol and propanoic acid
:
C
Esters are obtained from the reaction between carboxylic acid and alcohols.The reaction between methanoland propanoic acid in the presence of concentrated sulphuric acid leads to the formation of methyl propanoate, an ester.
$C{H}_{3}OH\left(aq\right)+C{H}_{3}C{H}_{2}COOH\left(aq\right)\to C{H}_{3}C{H}_{2}COOC{H}_3\left(aq\right)+H_{2}O\left(l\right)$

Answer: Option D. -> substitution reaction
:
D
A substitution reaction is a chemical reaction during which one atom or group of atoms in a chemical compound is replaced by another atom or group of atoms.
Chlorination of methane is a substitution reaction because chlorine atom replaces hydrogen atom from the methane molecule. The reaction occurs as follows:
${\text{CH}}_4\text{(g)}+{\text{Cl}}_2\text{(g)}\underset{}{\overset{\mathrm{sunlight}}{\to }}{\text{CH}}_3\text{Cl (g)}+\text{HCl (g)}\mathrm{Methane}\mathrm{Chlorine}\mathrm{Chloro}\mathrm{Hydrogen}\mathrm{methane}\mathrm{chloride}$

Answer: Option C. -> 2Na + 2CH3CH2OH →2CH3CH2ONa + H2
:
C
The reaction between sodium and alcohol is ametal-acidreaction. Metals generally liberate hydrogen on reacting with acids.
Ethanol reacts with sodium leading to the evolution of hydrogen and sodium ethoxide. The reaction occurs as follows:
$2\mathrm{Na}\left(s\right)+2{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}\left(\mathrm{aq}\right)\to 2{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{ONa}\left(\mathrm{aq}\right)+H_2\left(g\right)$

Answer: Option C. -> Methanol, Ethanol, Propanol, Butanol
:
C
A homologous series is a series of carbon compounds that have different number of carbon atoms but contain the same functional group and the consecutive members differ by a ${\text{CH}}_2$ group.
Methanol, ethanol, propanol and butanol are all alcohols and hence, belong to the same homologous series. They differ from each other by one ${\text{CH}}_2$ group.
In all the other options, even though they have same functional groups, the type of C-C bonds are different.