Question

at 20 degrees, the density of H2O is 1gmol/L but the density of D2O is 1.11g m/L

why is their a difference in the density of these 2 forms of water?

Answer 1

D2O weighs more than H2O (an extra neutron in every H -> D), and a carbon-deuterium bond is shorter than a carbon-hydrogen bond. More mass and more molecules per mL lead to a higher density.