The element that she discovered was radium.
In order to preserve substance, we must create a low temperature environment. In order to do this, we must remove the heat energy in the environment via reactions that will absorb heat energy. These are endothermic reactions. The answer is C.
The balanced chemical reaction would be as follows:
2H2O2 = 2H2O + O2
We are given the amount of the peroxide that decomposes. Using this as the starting point for the calculations, we can determine the amount of O2 produced. We do as follows:
14.3 mol H2O2 ( 1 mol O2 / 2 mol H2O2 ) = 7.15 mol O2 produced
