Question

A sample of pure compound contains 1.15g of sodium,3.01×10²² atoms of carbon and 0.1 mol of oxygen atom. Its empirical formula is ?

Answer 1

To find the empirical formula of the compound, you require the mole ratio of each element. The calculation is as follows: 

Moles of sodium:

moles = mass/molar mass
mass is given= 1.15g
molar mass = 23
Therefore moles =  1.15/23
                           = 0.05 moles

Moles of carbon: 
 
use Avogadro's constant:

                6.022 x 10 ^23 atoms = 1 mole
Therefore 3.01 x 10 ^22 atoms of carbon= 1 x 3.01 x 10^22  
                                                                     6.022 x 10^23

The mole of the carbon thus is, 0.05 moles

Moles of the oxygen:
The mole is given as 0.1

Find the mole ratio of the three elements:

       Na           :         C       :          O
       0.05               0.05               0.1
 
Divide everything by 0.05
 
            
                           1   :   1   :   2

Thus the empirical formula is,   NaCO2