Hydrogen

Some statements about heavy water are given below: Which of the above statements are correct?

1. (i) and (ii)
2. (i), (ii) and (iii)
3. (ii) and (iii)
4. (i) and (iii)

Answer

(1) (i) and (ii)

Solution

(i) Correct: D2O slows down fast neutrons, so it is used as a moderator in nuclear reactors.

(ii) Correct: D2O has higher melting point (276.8 K), boiling point (374.4 K) and viscosity than H2O because of stronger hydrogen (deuterium) bonding, i.e. it is more associated.

(iii) Incorrect: the dielectric constant of D2O (78.06) is lower than that of H2O (78.39), so ionic compounds dissolve less in it; it is a poorer solvent.

(i) and (ii) are correct.

Answer: (1)