Answer
A. 72.2 g
Explanation
Given:
Moles of Mg = 4.51 mol
Reaction: Mg + O₂ ----> MgO
What to find:
The grams of oxygen gas needed to completely burn 4.51 moles of Mg.
Step-by-step solution:
The first step is to balance the given chemical reaction.
Mg + 1/2O₂ ----> MgO
The next step is to calculate the number of moles of oxygen gas needed.
From the balanced reaction; 1 mol Mg reacts with 1/2 mol O₂
So, 4.51 mol Mg will react with:
[tex]\frac{4.51\text{ }mol\text{ }Mg\times\frac{1}{2}\text{ }mol\text{ }O_2}{1\text{ }mol\text{ }Mg}=2.255\text{ }mol\text{ }O_2[/tex]The final step is to calculate grams of oxygen in 4.5 moles of oxygen that was needed.
1 mole of O₂ = 32 grams
Therefore, 2.255 moles of O₂ = (2.255 x 32 grams) = 72.16 g = 72.2 g
The correct answer is:
A. 72.2 g
