Question

How many triple bonds are present in the compound `C_2H_2`?

Answer 1

One.

Explanation:

Your best strategy when dealing with such questions is to draw the Lewis structure of the molecule.

So, acetylene, `"C"_2"H"_2`, has a total of `10` valence electrons - `4` from each of the two carbon atoms and `1` from each of the two hydrogen atoms.

Now, when you draw a Lewis structure, you need to make sure that the atoms that are a part of the molecule have a complete octet.

SInce the hydrogen atoms can only form one bond, you know for a fact that will each be bonded to a carbon atom. This will account for `4` of the `10` valence electrons, `2` for each hydrogen - carbon single bond.

This means that the two carbo natoms must be bonded to each other. In order for them to have completel octets, you need to form a triple bond, which will use up the remaining `6` valence electrons, between them.

The Lewis structure will thus look like this

So, now you're redy to answer the question - each acetylene molecule has one triple bond. This triple bond consists of one sigma bond and two pi bonds.