Question

Determine the molecular formula for the following hydrocarbons: a. Hexane b. Methane c. Propyne d. 1-pentene e. 2-octyne f. Decane g. Heptane h. 4-nonene

Answer 1

Answer: The molecular formulas are written below.

Explanation:

Saturated hydrocarbons are defined as the hydrocarbons in which a single bond is present between carbon and carbon atoms. The general formula for these hydrocarbons is $C_nH_{2n+2}$

These hydrocarbons have the name ending with the suffix '-ane'

Unsaturated hydrocarbons are defined as the hydrocarbons which have double or triple covalent C-C bonds. They are known as alkenes and alkynes respectively. The general formula for these hydrocarbons is $C_nH_{2n}$ and $C_nH_{2n-2}$

The hydrocarbons having double and triple bonds have the name ending with the suffix '-ene' and '-yne' respectively.

For the given options:

Option a:  Hexane

'Hex' prefix is added for the chain having 6-Carbon atoms. So, the formula for this saturated hydrocarbon is $C_6H_{(2\times 6)+2}=C_6H_{14}$

Option b:  Methane

'Meth' prefix is added for the chain having 1-Carbon atom. So, the formula for this saturated hydrocarbon is $C_1H_{(2\times 1)+2}=CH_{4}$

Option c:  Propyne

'Prop' prefix is added for the chain having 3-Carbon atoms. So, the formula for this unsaturated hydrocarbon is $C_3H_{(2\times 3)-2}=C_3H_4$

Option d:  1-pentene

'Pent' prefix is added for the chain having 5-Carbon atoms. So, the formula for this unsaturated hydrocarbon is $C_5H_{(2\times 5)}=C_5H_{10}$. The double bond is present between C-1 and C-2 atoms

Option e:  Octyne

'Oct' prefix is added for the chain having 8-Carbon atoms. So, the formula for this unsaturated hydrocarbon is $C_8H_{(2\times 8)-2}=C_8H_{14}$

Option f:  Decane

'Dec' prefix is added for the chain having 10-Carbon atoms. So, the formula for this saturated hydrocarbon is $C_{10}H_{(2\times 10)+2}=C_{10}H_{22}$

Option g:  Heptane

'Hept' prefix is added for the chain having 7-Carbon atoms. So, the formula for this saturated hydrocarbon is $C_7H_{(2\times 7)+2}=C_7H_{16}$

Option h:  4-nonene

'Nona' prefix is added for the chain having 9-Carbon atoms. So, the formula for this unsaturated hydrocarbon is $C_9H_{(2\times 9)}=C_9H_{18}$. The double bond is present between C-4 and C-5 atoms