Question

Chemical analysis shows that citric acid contains 37.51 % C, 40.20 % H, and 58.29 % O. What is the empirical formula for citric acid?

Answer 1

Hint Empirical formula of a chemical is the modest whole number that gives the positive ratio of the atoms that are present in a particular compound. Empirical formula gives the idea of the number of individual atoms present in the chemical.

Complete step by step answer:
- In the question they have given data to calculate the empirical formula of citric acid.
- The given data in the question is citric acid contains 37.51 % C, 40.20 % H, and 58.29 % O.
- By using the above given data we should calculate the empirical formula of citric acid.
- First we should convert the percentage of each element into a number of moles using the below formula.
Number of an element = $\dfrac{\text{weight of the particular element}}{\text{molecular weight of the element}}$
Number of moles of carbon = $\dfrac{37.51}{12}=3.12moles$
Number of moles of hydrogen = $\dfrac{4.20}{1.0079}=4.17moles$
Number of moles of oxygen = $\dfrac{58.29}{15.999}=3.64moles$
- The number of moles of carbon is less among all the elements.
- Now divide all the moles of the elements with the number of moles of carbon then we will get $C{{H}_{1.34}}{{O}_{1.17}}$ .
- By multiplying the number of moles left as subscript with a number to make them as a proper number and the number will be ‘6’.
- After multiplying the subscripts in $C{{H}_{1.34}}{{O}_{1.17}}$ we will get ${{C}_{6}}{{H}_{8}}{{O}_{7}}$ .

- Therefore the empirical formula of citric acid is ${{C}_{6}}{{H}_{8}}{{O}_{7}}$ .

Note: We have to follow the above mentioned steps properly otherwise we won’t get a correct empirical value. Molecular formula of a compound is always a multiple of the empirical formula of the compound, sometimes the multiple number may be 1.