Answer:
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So that you can learn while being safe. Wearing goggles, for eye protection when dealing with chemicals
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 
Answer:
B. mass and height have the same effect on gravitational potential energy.
Explanation:
Both mass and height have the same effect on the gravitational potential energy of body.
Gravitational potential energy is the energy of a body due to that of another body. It usually the energy at rest in a body.
It is mathematically expressed as;
G.P.E = m x g x h
m is the mass
g is the acceleration due to gravity
h is the height
We see that both the height and mass are directly proportional to the gravitational potential energy and as such, they have the same effect.