Chapter 9, Problem 3CR

ow do we know that 16.00 g of oxygen Contains the same number of atoms as does 12.01 g of carbon, and that 22.99 g of sodium contains the same number of atoms as each of these? How do we know that 106.0 g of ${\text{Na}}_2{\text{CO}}_3$contains the same number of carbon atoms as does 12.01 g of carbon, hut three times as many oxygen atoms as in 16.00 g of oxygen, and twice as many sodium atoms as in 22.99 g of sodium?