Question

how many oxygen atom contained in 53 gram of Na2co3

Answer 1

Avagadro's constant states that 1 mole of any substance has 6.022 × 10²³ molecules/atoms.

Find the number of moles of 53 g of Na2CO3:
molar mass Na2CO3 = 23 × 2  + 12 + 16 × 3 = (46+12+48) = 106

moles = mass/molar mass
 
           = 53/106
           = 0.5 moles

1 mole = 6.022 ×10²³ atoms
Then 0.5 moles = 6.022 × 10²³ × 0.5 atoms
                     
                          = 3.011 × 10²³ atoms of Na2CO3