How many hydrogen atoms are represented in the formula #(CH_3)_2CH_2#?

1 Answer
Jan 7, 2016

Answer:

You have represented propane. There are 8 hydrogen atoms in this molecule.

Explanation:

How do you know there are 8 hydrogens? It is largely a matter of practice to look at a formula, and state it more simple terms.

You have #(H_3C)_2CH_2#; I could equally as correctly represent this as #H_3C-CH_2-CH_3#. Is this clear from the formula? I could condense the formula to give #C_3H_8#, i.e. 8 hydrogens as required.

So you have got propane, what about butane, #H_3C(CH_2)_2CH_3#, what about pentane, #H_3C(CH_2)_3CH_3#, what about hexane, #H_3C(CH_2)_4CH_3#? How many carbons in each molecule? And how many hydrogens? As the chain grows, of course, the opportunity for isomerism becomes greater. The general formula for alkanes is #C_nH_(2n+2)#. Do all the linear alkanes here obey this formula?