Here's why:

* Carbon (C) typically forms four bonds. In the formula KHC3, carbon would only have three bonds, which is unstable.

* Hydrogen (H) usually forms one bond. Here, it appears to be forming two bonds, which is unlikely.

It's possible you meant to write a different formula. Some common compounds containing potassium, hydrogen, and carbon include:

* Potassium bicarbonate (KHCO3): A common ingredient in baking powder.

* Potassium formate (KHCOO): Used in some chemical reactions.

If you could clarify the intended formula, I can help you identify the type of compound.