Question

Write the molecular formula of the fourth and fifth members of the homologous series of carbon compound represented by the formula CnH2n+1 OH.

Answer 1

Explanation:

(Fourth member-C4H9OH and Fifth member-C5H11OH)

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Answer 2

Answer:

The molecular formula of the $4^{th}$ member of the given homologous series of $C_{n}H_{2n+1}OH$ is $C_{4}H_{9}OH$.

The molecular formula of the $5^{th}$ member of the given homologous series of $C_{n}H_{2n+1}OH$ is $C_{5}H_{11}OH$.

Explanation:

Homologous series:

• It is a series of similar compounds in which the members differ from one another by an additional group, i.e., $CH_{2}$.
• Also, it is a series of chemical compounds that have the same functional group but differ in the formula by a fixed group of atoms.

As given,

• The homologous series of carbon compounds is represented by the molecular formula $C_{n}H_{2n+1}OH$.

1) The molecular formula of the fourth member of the given homologous series:

Therefore,

• n = 4

After putting the value of n = 4 in the given molecular formula, we get:

• $C_{4}H_{2(4)+1}OH$ = $C_{4}H_{9}OH$

Hence, the molecular formula is $C_{4}H_{9}OH$.

Also, the name of the compound is butanol.

2) The molecular formula of the fifth member of the given homologous series:

Therefore, 

• n = 5

After putting the value of n = 5 in the given molecular formula, we get:

• $C_{5}H_{2(5)+1}OH$ = $C_{5}H_{11}OH$

Hence, the molecular formula is $C_{5}H_{11}OH$.

Also, the name of the compound is pentanol.