Question

How many atoms of oxygen are present in 300g of CaCO3?

Answer 1

The formula unit mass of calcium carbonate can be calculated as follows

Formula unit mass of CaCO3 = Atomic mass of calcium + atomic mass of carbon + 3 X( atomic mass of oxygen)

= 40 + 12 + 3 x (16)

= 100u

Thus the molar mass of CaCO3 (that is the mass of 6.022 X 1023 particles) is 100g. So

100g of CaCO3 = 3 X 6.022 X 1023 atoms of oxygen

1g of CaCO3 = [( 18.066 X 1023 ) / 100] atoms of oxygen

300g of CaCO3 = [(18.066 X 1023 X 300) / 100] atoms of oxygen

= 54.198 X 1023 atoms of oxygen