Greetings,
sudanese engineer:, I'd like to welcome you and everyone new to the Chemical Forums, but I want to ask you to review our
Forum Rules{click}. You already accepted the rules when you signed up for our forum, and you have to follow them, whether you agree with them or not, or even if you're unaware of them.
We don't dump complete answers on this forum, not for a new student, not for a professional in a hurry, and not for an amateur trying to invent the latest thing. Its your responsibility to know the basics from the beginning, and be able to conduct the basics of an online search or a review of printed material.
What have you done, so far, to try to solve this problem for yourself?