Statements about heavy water are given below :
A. Heavy water is used in exchange reactions for the study of reaction mechanisms.
B. Heavy water is prepared by exhaustive electrolysis of water.
(C) Heavy water has higher boiling point than ordinary water.
(D) Viscosity of H₂O is greater than D₂O.
Choose the most appropriate answer from the options given below :

Solution

Chemistry ma’am · 2 steps

Heavier D makes everything in D₂O a little more sluggish: it boils higher and flows more slowly.

1. Why D2O differs. Deuterium is twice as heavy as protium, and D₂O forms slightly stronger hydrogen bonds than H₂O. Its molecules hold on to each other a little more tightly.

   Statement	True or false	Reason
   A: used in exchange reactions	True	D swaps with H in a compound, and tracing where D ends up reveals the mechanism.
   B: exhaustive electrolysis	True	H₂ is released faster than D₂, so the leftover water gets richer and richer in D₂O.
   C: higher boiling point	True	D₂O boils at 374.4 K, against 373.0 K for H₂O.
   D: H₂O more viscous	False	At 298 K, D₂O is about 1.107 cP and H₂O about 0.890 cP, so D₂O is the more viscous one.

2. So. A, B and C are correct and D is reversed, so the answer is (a).

The idea to keep. For D₂O vs H₂O, think stronger attraction: higher melting point, boiling point, density, viscosity and enthalpy of vaporisation. Only the ionic product and dielectric constant are lower.

Answer from the NTA final answer key. Solution by PrepWiser.