Rris is how u right it Mg=? Because it ask u a question and then you put the equal sign and then you put the question mark because you don't know it yet
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 
27*9=243 if one mole is equal to 27 grams times that by 9
Answer:
A Newman projection, useful in alkane stereochemistry, visualizes the conformation of a chemical bond from front to back, with the front atom represented by a dot and the back carbon as a circle. The front carbon atom is called proximal, while the back atom is called distal.
I believe it is because, Lead has a higher boiling point than zinc. by the time Lead melts and becomes a liquid, the temperature is way higher than the boiling point of Zinc therefore, Zinc becomes a gas.