Empirical and Molecular formula

Empirical formula :

To define the formula of empirical, we can say that the empirical formula of a compound is a ratio of atoms present in a molecule (or ion). An empirical formula is a simple whole-number ratio of the number of atoms of each type. If this equation is not a whole number it then becomes a molecular formula. 

• In the formula of empirical, no subscripts can be used to describe the number of atoms for any element that are not combined in molecules. In other words, an empirical formula only includes those elements that can be written as whole-number multiplies (or ratios) of each other. 
• The empirical formula definition or formula is written using only capital letters and the symbols for each element and they represent the numbers of atoms of the element in a compound. An empirical formula tells you that all compounds with this formula will contain this number of atoms, but it doesn’t tell you which elements make up the compound.
• The formula of empirical evidence gives a direct insight into how the elements make up the compound. The molecular mass and empirical formula directly give the total amount of each element in the compound. Specific gravity is also known as relative density is a measurement of density relative to water. It is dimensionless, being derived from a ratio of densities.

Empirical Formula = Molecular Formula/n

• An example of an Empirical Formula is when we calculate it for Boron Hydride which is BH3. The measured mass of the compound is 27.66g.

For empirical formula, we can see the atomic mass is 13.81 u = B + H(3) = 10.81 + 3

After this, we can calculate the molecular formula from the formula that has been stated above.

Molecular Formula :

A formula of molecules is a chemical formula that represents, in chemical terms, the simplest possible empirical formula of a chemical compound. It reveals the simplest, amount-of-element symbols and numbers that could represent a chemical substance. 

• A molecular formula provides more information than the structural formula, which is an arrangement of atoms in three dimensions like the shape of a cuboid. The molecular formula of a compound is the same as the formula weight. It is also referred to as a formula number. The molecular mass of a substance can be thought of as the total amount of matter that makes up a molecule. 

• A formula of a molecule is derived from the chemical empirical formula of a compound using the number of atoms in each molecule. Each molecule contains chemically identical groups of atoms called monomers, and these monomers are represented by symbols in the empirical formula.
• Molecules are the smallest particles of a chemical substance. Both an empirical formula and molecular formula are composed of the same elements but in different proportions. In the case of compounds, a molecular formula should add up to give you the same mass as compared to empirical formulas, which is given by the element’s atomic mass. 
• It basically has useful data that includes a detailed formula of the compound, its molecular formula, molecular weight, and structural formula, plus other goodies like boiling point, melting point, and density.

Molecular Formula  = n × Empirical Formula

• An example of a Molecular Formula is when we calculate it for Boron Hydride which is BH3. The measured mass of the compound is 27.66g.

For molecular formula, we can see the atomic mass is 13.81 u = B + H(3) = 10.81 + 3

From it, we can calculate the factor “n” given in the formula. As n is equal to Molecular Formula/Empirical Formula, so n comes out as 2.

N = 27.66/13.81

Now, when we put the value of n is equal to 2, the molecular formula comes out to be B2H6.

Drawbacks of using Empirical and Molecular Formula :

Empirical and molecular formulas tell us the same kinds of information. The difference between the two is that molecular formulas also give information about the arrangement of atoms in a molecule. 

• Empirical chemical formulas are derived from actual measurements, where the mass of each element is calculated directly or indirectly. Molecular formulas are derived by counting only the total numbers of atoms of each type in a molecule. 
• However, the biggest drawback of using both these formulas is that they are not applicable to the arrangements or they do not tell us anything about how the molecules are arranged there. 
• This means that the molecular formula is identical to the empirical formula except that each element must be multiplied by the number of its atoms in the compound. The molecular formula represents the actual number of each type of element contained in one molecule of the compound. 

The empirical formula represents the simplest ratio of elements that can combine to form this compound, thus determining the type of molecule. So, the drawbacks of Empirical and molecular formulae can be taken into account.

Conclusion : 

In this material, we got to learn about Empirical and molecular formulae and how they are used to determine the questions according to them. Moreover, the drawbacks of using Empirical and molecular formulae are well explained here, which will help the students to learn more about it. To understand the Empirical and molecular formulae, one can refer to this material and understand the topic well. The formulae that are used in the module will help you understand the concepts better, and you can solve the problems more efficiently.