The mass of C02 contains same number of molecules as there are number of atoms in 2.3 g of sodium

1- mole of any Substance will have the same number of Molecules.

Molecular weight of CO2= 44

Molecular weight of H20= 18

So 18 g of H20 will contain the same Number of molecules as in 44 g of CO2.

Therefore 7.2 g of H2O will have same Number of Moleculesas in =7.2/18 x 44

= 17.6 g of CO2.

yes it is balanced

if you mean hydrogen and oxygen then water is the product