Question

why is the percent yield should never rise above 100 percent

Answer 1

100% is the theoretical maximum amount you could possibly get. Any more would be impossible. Mass would not be conserved if you could obtain more than 100% yield.

Answer 2

thank you very much, but what do you mean by mass cannot be conserved if I will obtained more than 100%.

Answer 3

If you get more of something than what you could have possibly obtained, you may end up having more atoms of something than you had initially. That would violate the law of conservation of mass.