Isotopes of Hydrogen - UNSOLVED PRACTICE SET

Q7. Write the nuclear composition (protons, neutrons, electrons) of protium, deuterium, and tritium in a tabular form.

Q8. Why do the three isotopes of hydrogen have nearly identical chemical properties? Explain with reference to their electronic configuration.

Q9. Tritium is used in self-luminous exit signs and watch dials. Why is tritium preferred over other radioactive substances for such applications?

Q10. Deuterium is also called "heavy hydrogen." Why? Calculate how much heavier a D₂O molecule is compared to an H₂O molecule.

Q11. Explain why the bond dissociation energy of D–D is slightly higher than that of H–H.

Q12. Your school lab has a sample of water that is suspected to contain heavy water. Suggest one simple physical property you could measure to confirm the presence of D₂O.

Q13. Describe the three isotopes of hydrogen in detail — their discovery, nuclear composition, natural abundance, and physical properties. Why do they show identical chemical behaviour despite different masses?

Q14. Discuss the applications of deuterium and tritium in:

(a) Nuclear reactors (as moderators or fuel)

(b) Tracer studies in chemistry and biology

(c) Future energy sources (fusion reactions)

Also mention the hazards associated with handling tritium.

Q15. The existence of isotopes was first proven using hydrogen. Explain how the discovery of isotopes changed our understanding of atomic structure. Why is hydrogen particularly suitable for demonstrating isotopic effects?

Q16. The atomic masses of protium, deuterium, and tritium are approximately 1 u, 2 u, and 3 u respectively. The natural abundance of protium is 99.985%, deuterium is 0.015%, and tritium is negligible.

(a) Calculate the average atomic mass of hydrogen based on these abundances.

(b) Why does the calculated value differ slightly from exactly 1.008 u (the actual atomic mass of hydrogen)?

(c) If a 100 g sample of natural hydrogen gas is collected, what mass of it would be deuterium?

Q17. In heavy water (D₂O), the O–D bond is stronger than the O–H bond in normal water.

(a) If the bond dissociation energy of O–H is 463 kJ/mol and O–D is 470 kJ/mol, calculate the percentage increase in bond strength.

(b) Explain why this difference makes D₂O less reactive than H₂O in certain reactions.

(c) A 500 mL sample of D₂O has a density of 1.11 g/mL. Calculate its mass and compare it with the mass of 500 mL of H₂O (density = 1.00 g/mL).

Q18. Tritium has a half-life of 12.3 years and decays by beta emission.

(a) Write the nuclear equation for the decay of tritium.

(b) If you start with 1.0 g of tritium, how much will remain after 24.6 years?

(c) Why is tritium considered a promising fuel for future fusion reactors, and what is the main challenge in using it?