PROBLEM BASED ON MOLES OF MOLECULES | PRACTISE QUESTIONS | CLASS 10

 PROBLEM BASED ON MOLES OF MOLECULES 

1 mole of  molecules = Gram molecular mass of the substance = 6.022 * 10^23 molecules 

This gives us three relations :

(1) The first relation is :

     1 mole of molecules = gram molecular mass 

This relation can be used to convert the number of moles of molecules into mass in grams , and to convert the mass in grams into moles of molecules.

(2) The second relation is:

        1 mole of molecules = 6.022*10^23 molecules 

    by using this relation ,we can convert the moles of molecules into the number of molecules , and the number of molecules can be converted into moles of molecules.

(3) The third relation is :

     gram molecular mass = 6.022 *10^23 molecules

This relation is used to find out the number of molecules in a given mass of the substance and also to calculate the mass of a given number of molecules.

SAMPLE PROBLEMS FOR PRACTICE 

Q 1. What is the mass of each one of the following ?

(a) 1 mole of water (H2O)

Sol: 1 mole of H2O = Molecular mass of H2O in gram 

                                 = Mass of H *2 + Mass of O 

                                 =1*2 +16

                                 =18 gram

(b) 1 mole of ethanol (C2H6O)

 Sol: 1 mole of C2H6O=Molecular mass of C2H6O

= Mass of C * 2 +Mass of H *6 +Mass of O

=12*2+1*6+16

=46GRAM

(C). 1 Mole of C6H12O6

SOL: 1 Mole of C6H12O6=Molecular mass of C6H12O6

=Mass of C * 6+ mass of H *12 +mass of O*6