The answer is powder because if it was a small crystal it the molecules are tightly compact same with the small cube but there less compact, powder is loose and more spread out and easier to mix so it would react the fastest
C₃H₃O i think. tell me if i’m wrong
The answers would be the mass before a reaction is the same as the mass after a reaction which basically means mass is conserved
The ratio Potassium : Selenium is 39:78 but that can be simplified to 13:26 (divide each by 3) in grams. Hope this helps.