Question

How can I calculate the percent composition of magnesium oxide?

Answer 1

Hint:The chemical formula of magnesium oxide is MgO. It is formed of one magnesium atom and one oxygen atom. The formula of the percent composition is the same as the formula of mass percent where the mass of the atom is divided by the mass of the compound multiplied by 100.

Complete step by step answer:
The magnesium oxide is the chemical compound with molecular formula or chemical formula MgO. In every sample of substance there will be the same number of magnesium atoms and oxygen atoms.
The percent composition is calculated by dividing the mass of an atom by the total mass of the compound multiplied by 100.
The formula to calculate the percentage composition is shown below.
$C\mathrm{\%}={\displaystyle \frac{M_A}{M_T}}\times 100$
Where,
$C\mathrm{\%}$ is the percentage composition
$M_A$ is the mass of atom
$M_T$ is the total mass of the compound.
The atomic weight of magnesium Mg is 24.3. The atomic weight of oxygen is 16.0.
The total mass is (24.3+16.0 = 40.3)
To calculate the percent composition of magnesium, substitute the values in the given equation.
$\Rightarrow C\mathrm{\%}={\displaystyle \frac{24.3}{40.3}}\times 100$
$\Rightarrow C\mathrm{\%}=60.29\mathrm{\%}$
The percent composition of magnesium in magnesium oxide is 39.70 %.
To calculate the percent composition of oxygen, substitute the values in the given equation.
$\Rightarrow C\mathrm{\%}={\displaystyle \frac{24.3}{40.3}}\times 100$
$\Rightarrow C\mathrm{\%}=39.70\mathrm{\%}$
The percentage composition of oxygen in magnesium oxide is 39.70 %.
The total composition of magnesium oxide = (60.29 + 39.70 =99.99) $\approx$ 100%.

Note:
As magnesium is a metal and oxygen is a gas, magnesium is heavier than oxygen. So, the percent composition of the magnesium will be always greater than the percent composition of oxygen. When the mass of a given component of the chemical compound is provided then the value of mass is substituted to find the percent composition.