Question

How would you determine the empirical formula of a compound found to contain $52.11\%$ carbon, $13.14\%$ hydrogen, and $34.75\%$ oxygen?

Answer 1

Given that the empirical formula of a compound contains some percentage of carbon, hydrogen and oxygen atoms, by dividing these percentages with the molar mass gives the moles, the moles of each atom must divide with the lowest moles atom divides the mole ratio. The mole ratio gives the empirical formula.

Complete Step By Step Answer:
The empirical formula is the simplest mole ratio of a molecular formula.
Given that the empirical formula of a compound contains
Carbon percentage is given as $52.11\%$ , the molar mass of carbon is $12gmo{l^{ - 1}}$
The number of moles of carbon will be $\dfrac{{52.11}}{{12}}4.34moles$
Hydrogen percentage is given as $13.14\%$ , the molar mass of hydrogen is $1gmo{l^{ - 1}}$
The number of moles of hydrogen is $\dfrac{{13.14}}{1} = 13.14moles$
Oxygen percentage is given as $34.75\%$ , the molar mass of oxygen is $16gmo{l^{ - 1}}$
The number of moles of oxygen will be $\dfrac{{34.75}}{{16}} = 2.17moles$
Out of the moles of carbon, hydrogen and oxygen. Oxygen contains the least amount of moles. To obtain mole ratio, divide the moles of atom with the moles of oxygen
The mole ratio of $C:H:O$ will be $\dfrac{{4.34}}{{2.17}}:\dfrac{{13.14}}{{2.17}}:\dfrac{{2.17}}{{2.17}} = 2:6:1$
Thus, the empirical formula of the compound contains $52.11\%$ carbon, $13.14\%$ hydrogen, and $34.75\%$ oxygen is ${C_2}{H_6}O$ .

Note:
While calculating the empirical formula the simplest mole ratio must be considered. So, the moles of each atom were divided with moles of atoms containing a smaller number of moles. The molar mass must be exactly taken while determining the moles of an atom. The mass will be given in percentages or grams.