What happens when you swallow 7 grams of cocaine in a bag?

Depends on what type of bag. If you mean a sandwich type baggie, depending on how long it stays in your stomach, your stomach acids will dissolve it. If that's the only thing between the coke and your stomach, death may occur like happened to a friend of mine named TwoTon(R.I.P). Now if including the baggie the coke is in individual party type balloons your chances are better.

P.S.

My friend swallowed around 3 grams and at the wake you could see chemical burns around his mouth. Either way not a good idea to swallow illicit drugs.