Answer is: 0,275 moles of oxygen are consumed.
Chemical reaction: 2Mg + O₂ → 2MgO.
n(Mg) = 0,550 mol.
n(O₂) = ?
from chemical reaction: n(Mg) : n(O₂) = 2 : 1.
0,550 mol : n(O₂) = 2 : 1.
2n(O₂) = 0,550 mol.
n(O₂) = 0,275 mol.
n - amount of substance.
Explanation:
As the given chemical reaction equation is as follows.

Also, it is given that for 2 moles the energy required is 130 kcal. This means that energy required for 1 mole is calculated as follows.
1 mole = 
= 65 kcal
Hence, energy required for 7 moles will be calculated as follows.
Energy required = 
= 455 kcal
Thus, we can conclude that energy required to produce 7.00 mol
on the basis of given reaction is 455 kcal.
Physical properties can be observed or measured without changing the composition of matter. These are properties such as mass, weight, volume, and density. Remember that density is a physical property.
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