Question

What is the general formula for a straight-chain alkane? cnhn cnh2n+2 cnhn+2 cnh2n?

Answer 1

General formula for alkane is CnH2n+2

Answer 2

Option B:
`C_(n)H_(2n+2)`

Alkane is defined as series of hydrocarbons which are saturated (all the carbon-carbon bonds are single) for example: methane, ethane, propane etc.

In alkane, carbon has 4 valence electrons so, it can make single bonds with 4 hydrogen atoms.

In the series, the first alkane is methane, it has 1 carbon atom thus, 4 hydrogen atoms are attached to it and molecular formula becomes
`CH_(4)`. Similarly, the second alkane in the series is ethane, it has 2 carbon atoms, both attached with single bond. The remaining three electrons in each carbon are shared with 3 hydrogen atoms each thus, it has total of 6 hydrogen atoms. Molecular formula of ethane will be
`C_(2)H_(6)`.

Now, for general formula, let the number of carbon atoms be n thus, number of hydrogen atoms will be
`2n+2`

Therefore, general formula of straight chain alkane is
`C_(n)H_(2n+2)`.