Question

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

Answer 1

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?