Question

A compound is found to be $12.7\% $ carbon, $3.2\% $ hydrogen, and $84.1\% $ bromine. What is its empirical formula?

Answer 1

Hint: The empirical formula for a compound is defined as the ratio of subscripts of the fewest possible entire number of elements included in the formula. It is also referred to as the most basic formula. The formula of a substance expressed with the smallest integer subscript is called an empirical formula.
Solution
Formula used:
$Number{\text{ of moles = }}dfrac{{Mass}}{{Molar{\text{ mass}}}}$

Complete answer:
Assuming that the mass of unknown compound is $100g$ , we can say that it contains $12.7g$of carbon , $3.2g$ of hydrogen ,$84.1g$ of bromine.
We first need to calculate the moles of each element,
\[Moles{\text{ }}of{\text{ }}carbon = dfrac{{12.7g}}{{12gmo{l^{ - 1}}}} = 1.06mol\]
\[Moles{\text{ }}of{\text{ }}hydrogen = dfrac{{3.2g}}{{1gmo{l^{ - 1}}}} = 3.2mol\]
\[Moles{\text{ }}of{\text{ }}bromine = dfrac{{84.1g}}{{79.90gmo{l^{ - 1}}}} = 1.05mol\]
Dividing each number of moles by the smallest value of number of moles that is of bromine,
Using the formula,
$Number{\text{ of moles = }}dfrac{{Mass}}{{Molar{\text{ mass}}}}$
We get,
$Mole{\text{ ratio of carbon = }}dfrac{{1.06}}{{1.05}} = 1.009$
$Mole{\text{ ratio of hydrogen = }}dfrac{{3.2}}{{1.05}} = 3.047$
$Mole{\text{ ratio of bromine = }}dfrac{{1.05}}{{1.05}} = 1$
From the above values, we can conclude that the empirical formula is $C{H_3}Br$ .
Hence, the empirical formula is $C{H_3}Br$ .

Additional Information:
The molecular formula is a formula generated from molecules that represents the total number of individual atoms in a compound's molecule. A subscript in a molecular formula indicates the number of each type of atom in a molecule of the substance.

Note:
In most circumstances, the empirical rule is used to help determine outcomes when all of the data is not accessible. It lets statisticians or those who are studying the data – to see where the data will fall once everything is available. The empirical rule can also be used to determine whether a set of data is normal.