Question

sara made a mistake while balancing the following chemical equation:
$mg+o_{2}\to mgo$.
which explanation correctly describes why the chemical equation is unbalanced?
○a the number of molecules in the products of the equation are not the same as the reactants.
○b the number of atoms of the element oxygen in the reactants and products of the equation is not the same.
○c the number of atoms of the element magnesium in the reactants and products of the equation is not the same.
○d the number of atoms of the elements oxygen and magnesium in the reactants and products of the equation is not the same.

Explanation:

• For option A: Balancing is about atoms, not molecules. So this is incorrect.
• For option B: In the reactant \(O_2\), there are 2 oxygen atoms. In the product \(MgO\), there is 1 oxygen atom. The number of oxygen atoms is different. This is correct.
• For option C: In the reactant \(Mg\) (1 atom) and product \(MgO\) (1 atom), the number of magnesium atoms is the same. So this is incorrect.
• For option D: Magnesium atoms are balanced (1 on each side). Only oxygen is un - balanced. So this is incorrect.

Answer:

B. The number of atoms of the element oxygen in the reactants and products of the equation is not the same.