Types of chemical formula

chemical formula and its types.
1) empirical formula
2) molecular formula
3) formula unit

1. Chemistry Topic : Types of chemical formula Zahra Fazal

2. What is chemical formula? Compounds are represented by chemical formula It tells the types and number of atoms of element present in a compound For example: sodium chloride ( NaCl) Water ( H 2 O )

3. Types of chemical formula Chemical formula are of two types : Empirical formula Molecular formula

4. Empirical formula It is the simplest whole number ratio of atoms present in a compound. The empirical formula is determined by knowing the percentage composition of a compound

5. Examples of empirical formula The covalent compound silica (sand) has simplest ratio of 1:2 of silicon and oxygen respectively therefore it’s empirical formula is SiO 2 . Formula of glucose is C 6 H 12 O 6 so its simplest whole number ratio is. C : H: O 6: 12:6 1: 2: 1 empirical formula = CH 2 O Of glucose

6. Formula unit It is the simplest whole number ratio of ions present in ionic compounds. The simplest unit taken as representative of ionic compound is called formula unit.

7. Example of formula unit Formula unit of common salt consist of one Na + and one Cl - ion so its empirical formula is NaCl

8. Molecular formula It show actual number of atoms of each element present in a molecule of that compound. Molecules are formed by the combination of atoms. These molecules are represented by molecular formula.

9. Examples of molecular formula Molecular formula of benzene is C 6 H 6 Molecular formula of hydrogen per oxide is H 2 O 2 Molecular formula of glucose is C 6 H 12 O 6 .

10. Relationship between empirical and molecular formula Molecular formula is derived from empirical formula by following relationship molecular formula= (empirical formula) n . n = 1,2,3…..and so on

11. Some compounds with their empirical and molecular formulae Compound Empirical formula Molecular formula Hydrogen peroxide HO H 2 O 2 Benzene CH C 6 H 6 Glucose CH 2 O C 6 H 12 O 6

12. Some compounds may have same empirical and molecular formula; For example : HCl , H 2 , SiO 2