17) 8.4 / 20 x 100
18) 20 . 0.5150
19) 6,50% because (as you said) the law of definite proportions states that regardless of the amount, a compound is always composed of the same elements in the same proportion by mass
At higher temperature, and lower pressure.
I believe it is C; reasoning being that the hint for physical change is," the producing of a gas," chemical "that's new and diff. substance. "
The answer is B. Below freezing
Heyo, I believe that the answer would be D. The valence electrons are given up by the K and gained by the F.