Question

A certain compound has an empirical formula of CH3. What must be true about this compound?

A. It contains three times as many hydrogen atoms as carbon atoms.
B. It consists of 75% hydrogen by mass.
C. Each molecule contains exactly four atoms.
D. Each carbon atom is bonded to three hydrogen atoms.

Answer 1

D. Each carbon atom is bonded to three hydrogen atoms. I immediately know that B is wrong, and while A and C are true, I don't think they are answers they are looking for.

Answer 2

Answer: A. It contains three times as many hydrogen atoms as carbon atoms.

Explanation: Empirical formula is the formula which shows the atoms of the elements in the simplest ratio of atoms whereas molecular formula show the actual number of atoms.

Thus if a compound has an empirical formula of
`CH_3`, it means there are thrice number of hydrogen atoms as carbon atoms.

The molecular formula could be written as
`[CH_3]_n`. Thus if number of carbon atoms are n, the number of hydrogen atoms are 2n.