No, empirical formula and general formula are not the same.
While both are types of chemical formulas, they represent different aspects of a compound's composition:
-
Empirical Formula: This shows the simplest whole-number ratio of atoms in a compound. It's the most reduced form of a compound's formula.
-
General Formula: This is a generic formula used to represent a whole class of compounds, usually organic compounds, with a specific functional group or homologous series. It represents the ratio of elements in the series in terms of 'n' where n can be any integer.
Here's a breakdown with examples:
Empirical Formula Explained
The empirical formula is derived from the molecular formula by dividing the subscripts by their greatest common factor. If the molecular formula already represents the simplest whole-number ratio, then the empirical and molecular formulas are the same.
-
Example 1: Glucose has a molecular formula of C6H12O6. The greatest common factor of 6, 12, and 6 is 6. Dividing each subscript by 6, we get the empirical formula CH2O.
-
Example 2: Water has a molecular formula of H2O. Since the ratio 2:1 cannot be further simplified, the empirical formula is also H2O.
General Formula Explained
General formulas are typically used for organic compounds to define homologous series. They show the relationship between the number of carbon atoms and other atoms present in the compound.
-
Example 1: Alkanes have the general formula CnH2n+2, where 'n' represents the number of carbon atoms. For example, if n = 3 (propane), the formula is C3H8.
-
Example 2: Alkenes have the general formula CnH2n, where 'n' represents the number of carbon atoms. For example, if n = 2 (ethene), the formula is C2H4.
Key Differences Summarized
| Feature | Empirical Formula | General Formula |
|---|---|---|
| Represents | Simplest whole-number ratio of atoms in a compound | A whole class of compounds (typically organic) |
| Specificity | Specific to an individual compound | Applies to a homologous series or a class of compounds |
| Form | A fixed ratio (e.g., CH2O) | An algebraic expression with 'n' (e.g., CnH2n+2) |
| Usefulness | Determining the simplest composition of a compound | Predicting the formulas of members within a chemical series |
In Conclusion
Empirical formulas provide the simplest ratio of elements in a specific compound, while general formulas describe the elemental ratios characteristic of an entire series or class of compounds. Therefore, they are distinct concepts with different applications in chemistry.
