Hi guys,
I want to know with a cpu core i7 how much hash I can check? is rational use use PC computer to mine bitcoin?
Sorry, carlosbtc, it's not rational to mine at all at the moment. Not CPU, not GPU, not Asic, not Scrypt Asic, not Cloud mining either.
Electrical costs, electrical capacity, Cooling costs, Hosting costs, Maintenance costs, Service costs, hidden costs in Cloud mining all contribute to you being a loser the moment you step into any type of mining.
If you're doing it for hobby, fun, and to learn about it, get like a Rockminer R-box or used Antminer S1 or S3. You'll get a bunch of BTC dust or some pocket change, but at least you'll be able to say you're Bitcoin mining.
Easiest and least painful way to get some Bitcoins, is to buy it from a trusted exchange or trusted seller.
Before jumping at all, read up all you can about Bitcoin, and don't be afraid to ask questions in this forum. Good luck!