Question

# How can I calculate the empirical formula of magnesium oxide?

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Hint:. The empirical formula is the predicted formula of the compound based on calculating the total number of atoms present in the given compound which includes several steps where this fact gives the required answer.

- In the classes of chemistry, we have studied about the concepts of basic chemistry which tells us about the empirical formula and also about the molecular formula of the given compound.
- Let us now recall these concepts so that we can deduce the empirical formula for the given compound in the question.
- Empirical formula is basically the one which gives the simplest positive integer ratio atoms present in the compound.
- Empirical formula can be calculated starting by converting the given mass of each element to moles using the data of molar mass from the periodic table. In the similar way, the empirical formula for magnesium oxide can be calculated.
- In the next step, divide each mole value by the smallest number of moles among the calculated one.
- The next step involves rounding off the obtained value to the nearest whole number. This gives the mole ratio of the element and is represented by the subscripts in the empirical formula.
Thus, we can assume that 0.297g of magnesium is heated to obtain 0.493 g of magnesium oxide.
mass of Mg will be = 0.297g
Mass of magnesium oxide = mass of Mg + mass of oxygen
$\Rightarrow$ mass of oxygen = $0.493 - 0.297 = 0.196g$
Moles of Mg = 0.297$\times \dfrac{1mole~Mg}{24.3g~Mg} = 0.012~mol$ of Mg.
Moles of oxygen $=0.196\times \dfrac{1mol~of~O}{16g~O} = 0.012~mol$
Since both the values are same, we can say that each atom is in the ratio 1 : 1
Thus, the empirical formula of magnesium oxide is $MgO$

Note: Note that empirical and molecular formula both may or may not have the same number of atoms present but the total whole integer obtained for the empirical formula will be multiplied with the actual number of atoms present and this will give the molecular formula.