How do I remove carpet from a cement porch?

More details would help but I assume your carpet is glued down and you need to get the glue up. Sorry no miracle chemical here other than elbow grease and a sharp sraper or razor. Once the carpet is up you can soften, dissolve and remove the glue with adjhesive remover. Before buying any chemicals try a pan of boiling water, allow to soak for 1 minute and then scrape with a putty knife, it may work.

Spry Acatone over the carpet, let it set for about ten minutes and the carpet will pull up

Acetone is extremely flammable and somewhat toxic. As a retired chemist, I would not recommend this procedure.