Heavy water, D2O has molecular mass of _____.

The correct answer is Option (1) → 20

Heavy water is water in which both hydrogen atoms are deuterium, the isotope of hydrogen with one proton and one neutron, so its atomic mass is 2 instead of 1.

• D₂O \(=2\times2+16=20\) u

• Ordinary water H₂O \(=2\times1+16=18\) u

Heavy water is used as a moderator in nuclear reactors to slow down neutrons.