What is Chemical Formula?
The symbolic representation of a compound that shows elements in the compound and also the ratio of their atoms is called chemical formula.
As elements are represented by symbols .
Similarly, compounds are symbolically represented by chemical formulas .
CHEMICAL FORMULAS :
Calcium Carbonate = CaCO3
Water = H2O
Sulphuric acid = H2SO4
Benzene = C6H6
Types of Chemical Formulas:
There are different types of chemical formulas of a compound .i.e.. empirical formula, molecular formula ,structural formula etc.
The chemical formula that gives the simplest or the most reduced whole number ratio of atoms present in a compound is called empirical formula.
Benzene = CH
The chemical formula that gives the actual number of atoms present in one molecule of a compound is called molecular formula.
Molecular formula of Benzene is C6H6
Molecular formula of Glucose is C6H12O6
Why some compounds have same empirical and molecular formula ?
If the compound’s chemical formula can not be reduced any more then their empirical formula is the same as molecular formula .
Important questions for Exams !!!
Vinegar is 5% acetic acid . This contains 2 carbon atoms , four hydrogen atoms and 2 oxygen atoms. Write its empirical and molecular formulas ?
Number of carbon atoms = 2
Number of hydrogen atoms = 4
Number of oxygen atoms = 2
Find out its empirical and molecular formulas
Molecular formula = C2H4O2
Finding Empirical formula as follow:
Empirical formula = CH2O
Caffeine ( C8H10 N4 O2) is found in tea and coffee . Write its empirical formula ?
molecular formula = C8H10 N4O2
Find out its empirical formula
Empirical formula = C4H5 N2O
Difference b/w Empirical & Molecular Formula:
|Empirical Formula||Molecular Formula|
|Simplest or most reduced whole number ratio of atoms|
present in a compound
Actual number of atoms present in a molecule
of a compound
|Determined directly by different methods|
Combustion analysis ,
|Can never determined directly, only determined as follow:|
Molecular formula = n x (Empirical formula)
|Empirical formula is used for all compounds||Molecular formula is used for only molecular compounds|
Glucose = CH2O
Water = H2O
Glucose = C6H12O6
Water = H2O
Significance or Importance of a chemical formula:
i)It is a shorthand Expression
ii) It shows different kinds of elements present in a compound
iii) It shows the ratio of atoms present in a compound
iv) It represents one molecule or one Formula unit of a compound
v) It represents one mole of a compound
vi) It shows the number of atoms present in one molecule
vii) It shows the number of Ions present in one Formula unit
vii) It shows the number of moles of each element in one mole of a compound
For e.g one molecule of Sulphuric acid (H2SO4) contains 2-atoms of H, 1-atom of Sulphur, and 4 – atoms of oxygen. One mole of H2SO=4contains= 2 moles of H, 1-mole of S, and 4-moleOxygen-atoms.
Types of Chemical Formula ( in Urdu / Hind)
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