Answer:
C
Explanation:
2Mg + O2 → 2MgO
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Considering the law of conservation of matter, the correct answer is third option: 2 Mg + O₂ → 2 MgO
The law of conservation of matter states that since no atom can be created or destroyed in a chemical reaction, the number of atoms that are present in the reagents has to be equal to the number of atoms present in the products.
Then, you must balance the chemical equation. For that, you must first look at the subscripts next to each atom to find the number of atoms in the equation. If the same atom appears in more than one molecule, you must add its amounts.
So, in the case of Mg + O₂ → MgO, you have:
The coefficients of each molecule below indicate the amount of each molecule for the reaction. This coefficient can be modified to balance the equation, just as you should never alter the subscripts.
By multiplying the coefficient mentioned by the subscript, you get the amount of each element present in the reaction.
So, balancing the O to obtain the same amount in the reactants and products you get:
Mg + O₂ → 2 MgO
So you have:
Since you still don't have the same amount of Mg on both sides, the equation is not balanced. Therefore, balancing the equation again:
2 Mg + O₂ → 2 MgO
So you have:
Now you have the same amount of each element on each side of the reaction, so the reaction is balanced.
Finally, the correct answer is third option: 2 Mg + O₂ → 2 MgO
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