General formula of the homologous series of alkanes is $C_{n} H_{2 n + 2}$ . Write down the molecular formula of the $8^{th}$ and $12^{th}$ member using this.

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Solution

The general formula for alkanes is $C_{n} H_{2 n + 2} .$

For $8^{th}$ member, n=8
So, $C_{8} H_{2 x 8 + 2} = C_{8} H_{18}$

For $12^{th}$ member, n=12
So, $C_{12} H_{2 x 12 + 2} = C_{12} H_{26}$

The general formula for $8^{th} member is C_{8} H_{18}$ $and for 12^{th} member is C_{12} H_{26} .$

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Similar questions

(a) Give the general name of the class of compounds having the general formula $C_{n} H_{2 n - 2} .$ Write the name of the first member of this homologous series.
(b) The general formula of a homologous series of carbon compounds is $C_{n} H_{2 n} .$ Write the molecular formulae of the second and fourth members of the series.
(c) Write the molecular formulae of the third and fifth members of homologous series of carbon compounds represented by the general formula $C_{n} H_{2 n + 2}$

Q. Write the molecular formulae of the third and fifth members of homologous series represented by the general formula C_nH_2n₋₂.

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(c) Name any two fossil fuels.

Q. Fill in the blanks by choosing words from the given list of words:
addition, carbohydrates, C_nH_2n−2, C_nH_2n_{+ 2}, electrochemical, homologous, hydrocarbons, saturated, substitution, unsaturated.
The alkanes form a ....... series with the general formula .......... The alkanes are .........., which generally undergo ........... reactions.

C_{n} H_{2 n + 2}

is the general formula of a homologous series of hydrocarbons.
i) Is this series saturated or unsaturated?
ii) Name the series described above. Give the formula and name of the member with two carbon atoms.
iii) Draw the structural formula of the first member of this series.
iv) Define the homologous series and find the common difference between the successive members of this family.
v) Write the formula of n-butane and n-pentane.

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General formula of the homologous series of alkanes is CnH2n+2. Write down the molecular formula of the 8th and 12th member using this.

The general formula for alkanes is CnH2n+2. For 8th member, n=8 So, C8H2x8+2 = C8H18 For 12th member, n=12 So, C12H2x12+2 =C12H26 The general formula for 8th member is C8H18 and for 12th member is C12H26.

General formula of the homologous series of alkanes is $C_{n} H_{2 n + 2}$ . Write down the molecular formula of the $8^{th}$ and $12^{th}$ member using this.

The general formula for alkanes is $C_{n} H_{2 n + 2} .$

For $8^{th}$ member, n=8
So, $C_{8} H_{2 x 8 + 2} = C_{8} H_{18}$

For $12^{th}$ member, n=12
So, $C_{12} H_{2 x 12 + 2} = C_{12} H_{26}$

The general formula for $8^{th} member is C_{8} H_{18}$ $and for 12^{th} member is C_{12} H_{26} .$