Question

Balance the equation: $\mathrm{Mg}+{\mathrm{O}}_2\to \mathrm{MgO}$

Answer 1

• Given the unbalanced chemical equation : $\mathrm{Mg}+{\mathrm{O}}_2\to \mathrm{MgO}$
• Compare the total number of atoms of each element on the reactant side and the product side.

Element	Reactant side	Product side
Magnesium($\mathrm{Mg}$)	1	1
Oxygen($\mathrm{O}$)	2	1

• Now, stoichiometric coefficients are added to molecules containing an element that has a different number of atoms on the reactant side and the product side.
• The coefficient must balance the number of atoms on each side.
• In order to balance Oxygen($\mathrm{O}$) multiply $2$on the product side.

Element	Reactant side	Product side
Magnesium	1	1
Oxygen	2	2

• Reaction becomes, $\mathrm{Mg}+{\mathrm{O}}_2\to 2\mathrm{MgO}$
• Now, the number of atoms of the elements on the reactant and product side must be updated.
• The above step is repeated until all the number of atoms of the reacting elements are equal on the reactant and product side. In this example, hydrogen is balanced next. The chemical equation is transformed as follows.
• Now to balance Magnesium multiplied by $2$ on the reactant side.

Element	Reactant side	Product side
Magnesium	2	1
Oxygen	2	2

• Reaction becomes, $2\mathrm{Mg}+{\mathrm{O}}_2\to 2\mathrm{MgO}$
• The overall balance equation, $\underset{\mathrm{Magnesium}}{\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Magnesium}\mathrm{Oxide}}{\mathrm{MgO}\left(\mathrm{s}\right)}$
• Now, the above chemical equation is balanced.