Question

Predict the molecular formula of a three-carbon alkyne.

Answer 1

.A three carbon molecule has three carbons. Duh. Meaning it has two bonds. It looks like this:

C-C-C.

It tells you it's an alkyne. Alk-YNE means it has at least one TRIPLE bond. Because there are only two bonds in the molecule, you know that the triple bond has to involve the central C carbon. And because that central C carbon can only form four bonds (i.e., it has four valence electrons it can share), and three of them are involved in a triple bond with one of the other carbons, you know it's bonded to the remaining carbon with a single bond.

C-C---C.

Where C---C is a triple bond, because I can't type three bars on top of each other.