Question

What is the empirical formula of Caffeine $$(C_8{H}_{10}{N}_4{O}_2)$$, a substance found in tea and coffee?

Answer 1

Hint: The empirical formula of any compound can be calculated easily using the following formula.
$$\text{Molecular formula = n}\times \text{empirical formula}$$
In order to use this formula, we must be knowing either molecular formula or empirical formula.

Complete step by step solution:
- Empirical formula is the simplest formula which provides the lowest whole number ratio of the element present in the compound.
- Relative Number of all the elements present in the compound can be found using the empirical formula.
- Empirical formula can be calculated using this formula
$$\text{Molecular formula = n}\times \text{empirical formula}$$
- Molecular formula is the multiple of the empirical formula.
- Molecular formula gives the actual number of elements present in the compound.
For example, in acetylene:
-$$C_2{H}_2$$is the molecular formula and $$CH$$is the empirical formula.
For caffeine, the molecular formula is $$(C_8{H}_{10}{N}_4{O}_2)$$
Using the formula, Molecular formula = n. empirical formula
where n is taken as the lowest number of elements present in the compound.
Oxygen atoms are present in the lowest quantity. So, n is taken as 2.
$${\text{C}}_8{\text{H}}_{10}{\text{N}}_4{\text{O}}_2\text{ = 2 }\times \text{ Empirical formula}$$
$$\text{Empirical formula =}{\displaystyle \frac{C_8{H}_{10}{N}_4{O}_2}{2}}$$
$$\text{Empirical formula = }{\text{C}}_4{\text{H}}_5{\text{N}}_2\text{O}$$

Therefore, empirical formula of caffeine is $${\text{C}}_4{\text{H}}_5{\text{N}}_2\text{O}$$.

Additional information:
-Caffeine is Methylxanthine alkaloid. It is found in coffee seeds, tea leaves, nuts, etc.
- Its IUPAC name is $$1,3,7-Trimethylpurine-2,6-dione$$.
- It is a stimulant for the central nervous system.

Note: -Empirical formula and molecular formula are different from each other.
- Molecular formula gives actual number of elements present in the compound whereas empirical formula gives lowest whole number ratio of the element present in the compound.