Question

what mass of water will contain the same number of molecules as 8gm of ferrous oxide​

Answer 1

Mass of FeO is 56+16=72g

no of molecules=8/72 ×NA

=1/9 NA

mass of H2O is 2+16=18

so equation is

m/18 ×NA=1/9 ×NA

m/2=1

m=2

so, your answer is ready

mass of water is 2g