Answer: 72 grams of 
are needed to completely burn 19.7 g 
Explanation:
According to avogadro's law, 1 mole of every substance weighs equal to molecular mass and contains avogadro's number 
of particles.
To calculate the number of moles, we use the equation:
Putting in the values we get:
According to stoichiometry:
1 mole of 
requires 5 moles of oxygen
0.45 moles of require= 
moles of oxygen
Mass of 
72 grams of are needed to completely burn 19.7 g
The smallest unit that can exist as an element and still have proprieties of that element is an Atom<span />
Answer choice A, B, and C is right about the valence electrons. For answer choice D and E, Would in it be a more of an element kind of choice. whether the element is closer to the left side of the periodic table or not determines the high and low energy.
