TEST YOURSEF 1.4 Chemistry 9th Chapter 1

TEST YOURSEF 1.4

(1) What is the relationship between empirical formula and formula unit?

The empirical formula shows the simplest ratio of atoms in covalent compounds. While the formula unit shows the simplest whole number ratio of ions as present in the ionic compound. Since both tell us the simplest units of compounds and simplest ratio. So, they are equal and same for covalent as well as ionic compounds.

 

(2) How can you differentiate between molecular formula and empirical formula?

     

Sr.No	Molecular Formula	Empirical Formula
1	Molecular formula shows the actual number of atoms of each element in a molecule of that compound.	Empirical formula shows the simplest whole number ratio of atoms present in a compound.
2	Example:C6H6(Benzene) ,C6H12O6(Glucose) etc	Example:CH(Benzene) ,CH2O(Glucose)etc.

Remember :

                     Some compounds may have same empirical formula and molecular formula e.g. H₂O, HCl etc.

(3) Identify the following formulae as formula units or molecular formula?

Sr.No	Molecular Formula	Empirical Formula
1	H2O2, C6H12O6	BaCO3

            CH₄ and C₁₂H₂₂O₁₁ have same empirical and molecular formula.

(4)   What is empirical formula of acetic acid (CH₃COOH)? Find out its molecular mass.

The acetic acid is actually C₂H₄O₂. The empirical formula of acetic acid is CH₂O.

Molecular mass :

CH₃COOH = (2*23)+(1*32)+(4*16)

=24+32+64

= 60 amu

(5)     Calculate the formula masses of :

          Na₂SO₄, ZnSO₄ and CuCO₃

Na₂CO₃ = (2*23) + ( 1*32) + (4*16)

                                                = 46+32+64

                                                = 142 amu

ZnSO₄ = (1*65) + (1*32) + (4*16)

                                               = 65+32+64

                                               = 161 amu

CuCO₃ = (1*63.5) + (1*12) + (3*16)

                                              = 63.5+12+48

                                              = 123.5 amu