Question

There are three isotopes of hydrogen and three naturally occuring isotopes of oxygen `(""^(16)O, ""^(17)O and ""^(18)O)`. How many kinds of water molecules are possible . Write their formulae.

Answer 1

18 . Their formulae are :
`H-""^(16)O-H, H-""^(17)O-H, H-""^(18)O-H, H-""^(16)O-D, H-""^(17)O-D,H-""^(18)O-D,H-""^(16)O-T,H-""^(17)O-T,H-""^(18)O-T, D-""^(16)O-D,D-""^(17)O-D,D-""^(18)O-D,T-""^(16)O-D,T-""^(17)O-D,T-""^(18)O-D,T-""^(16)O-T,T-""^(17)O-T,T-""^(18)O-T`
However, most abundant heavy water occuring in ordinary water is deuterium oxide, i.e., `D-""^(16)O-D`.