The fundamental composition of any chemical substance is communicated through a chemical formula. These formulas use elemental symbols and numerical subscripts to represent the atoms that form a compound. Different types of chemical formulas exist to convey specific information, and distinguishing between them is necessary for accurate scientific communication. The question of whether the formula C2H6 is an empirical formula depends on the rules governing its construction.
What Defines Empirical and Molecular Formulas
The molecular formula of a compound provides the precise count of every atom of each element in one molecule. For example, the sugar glucose has the molecular formula C6H12O6, indicating exactly six carbon atoms, twelve hydrogen atoms, and six oxygen atoms in every molecule.
In contrast, the empirical formula shows only the simplest whole-number ratio of the atoms within a compound. To determine the empirical formula from a molecular formula, one must find the greatest common divisor (GCD) of all the subscripts and divide them accordingly.
The molecular formula is always a whole-number multiple of the empirical formula. For instance, if a formula cannot be simplified further because the greatest common divisor of its subscripts is one, then the empirical formula and the molecular formula are identical.
Analyzing the Formula C2H6
The formula C2H6 represents the hydrocarbon compound known as ethane. Ethane is a colorless, odorless gas that belongs to the alkane family of organic molecules. In this formula, the subscripts indicate that the molecule contains two carbon atoms and six hydrogen atoms.
To determine if C2H6 is an empirical formula, the ratio of the atoms must be checked for simplification. The ratio of carbon to hydrogen atoms in ethane is 2:6. Since the numbers two and six share a common divisor greater than one, the formula can be reduced.
The greatest common divisor for 2 and 6 is 2. Dividing both the carbon subscript (2) and the hydrogen subscript (6) by 2 results in the new ratio 1:3. Therefore, the empirical formula for ethane is CH3. Because the ratio of atoms in C2H6 can be simplified, the formula C2H6 is not the empirical formula; it is the molecular formula for ethane. The molecular formula is two times the empirical formula CH3.
Some compounds, like water (H2O) or carbon dioxide (CO2), have molecular formulas that cannot be reduced further, meaning their empirical and molecular formulas are the same. However, the molecular formula C2H6 is a multiple of its simplest ratio, which confirms it is not the empirical formula.