Answer
a
Explanation:
the giraffe doesn't need carbon dioxide
Nitrogen and oxygen are the most prevalent in the atmosphere.
Answer :
According to the law of conservation of mass, the mass of reactants must be equal to the mass of products.
The balanced chemical reaction is,

As we know that the molar mass of magnesium is 24 g/mole, the molar mass of
is 32 g/mole and the molar mass of magnesium oxide is 40 g/mole.
From the given balanced reaction, we conclude that
As, 1 mole of magnesium react
mole of oxygen to give 1 mole of magnesium oxide.
So, the mass of Mg is 24 g, the mass of
and the mass of MgO is 40 g.
That means 24 g of Mg react with 16 g
to give 40 g of MgO.
Answer: 2.88×
atoms 
Explanation: First, using stoichiometry, we must convert this from grams to moles, then from moles to atoms.
1. For the first step, we should also look at the periodic table to find the molar mass of the compound, then use that as the denominator.

2. Now that it is converted to moles, we must convert it to atoms by multiplying it by Avogadro's number.

With this information, we know that there are
total atoms in 0.680 grams
.
I hope this helps! Pls give brainliest!! :)