Class 11 Chemistry Ch-9 Hydrogen (VSQ)

Q.1. Why is 2-ethylanthraquinone preferred in the commercial production of H2O2?

Answer Answer: It gets regenerated during the reaction by hydrogenation of 2–ethylanthrahydroquinone.

Q.2. Which would have higher electrical conductivity H2O or D2O?

Answer Answer: Water due its greater degree of dissociation
(pKH2O = 13.997 pKD2O = 14.869) .

Q.3. Give an example to show that ionic hydrides forms complexes.

Answer Answer: 8LiH + Al2Cl6 → 2LiAlH4 + 6LiCl

Q.4. Anhydrous BaO2 is not used for preparing H2O2. Why?

Answer Answer: Anhydrous BaO2 is not used because the BaSO4 formed during the reaction forms a protective layer around unreacted BaO2 and the reaction stops after some time.

Q.5. Why H2 gas is not found in earth’s atmosphere?

Answer Answer: Earth does not possess enough gravitational pull to retain light H2 molecule, therefore it is not found in our atmosphere.

Q.6. Give the order of reactivity of dihydrogen with the halogens.

Answer Answer: The decreasing order is F2 > Cl2 > Br2 > I2. The reaction with fluorine occurs even in the dark whereas with iodine it requires a catalyst.

Q.7. What is the reason for hardness of water ?

Answer Answer: Hardness of water is due to the presence of bicarbonates , chlorides and sulphates of calcium and magnesium in water.

Q.8. Which gas is evolved when Mg3N2 (magnesium nitride) is treated with H2O? Give chemical reaction.

Answer Answer: NH3 gas is evolved.
Mg3N2 + 6H2O → 3Mg(OH)2 + 2NH3.

Q.9. How is heavy water produced from ordinary water?

Answer Answer: It is obtained by repeated electrolysis of ordinary water.

Q.10. Why does hard water react with soap?

Answer Answer: Hard water containing Ca2+ and Mg2+ ions react with soap to form insoluble substance, i.e., calcium or magnesium salt of fatty acid.

Q.11. Which compounds cause temporary hardness of water?

Answer Answer: Ca(HCO3)2 and Mg(HCO3)2.

Q.12. How would you prepare a sample of ND3?

Answer Answer:

Q.13. Which isotope of hydrogen does not have neutron?

Answer Answer: H(1,1) does not have neutron. It is called protium or ordinary hydrogen.

Q.14. What is the trade name of sodium hexa-metaphosphate?

Answer Answer: Calgon

Q.15. What is cause of bleaching action of H2O2 ?

Answer Answer: Refer theory

Q.16. Which types of hydrides are generally non-stoichiometric in nature?

Answer Answer: Interstitial hydrides are generally non-stoichiometric in nature.

Q.17. How does heavy water react with Al4C3?

Answer Answer: Al4C3 + 12D2O → 4Al(OD)3 + 3CD4

Q.18. Why is hydrogen molecule highly polar?

Answer Answer: It is due to small size of hydrogen atom and high electronegativity.

Q.19. What is the action of water on hydrolith?

Answer Answer: CaH2 + 2H2O → Ca(OH)2 + 2H2

Q.20. What is the trade name of H2O2 used as antiseptic?

Answer Answer: H2O2 commercially is called perhydrol.

Q.21. Arrange H2, D2 and T2 in the decreasing order of their boiling points.

Answer Answer: T2 > D2 > H2

Q.22. What is the molecular mass of the compound formed by burning tritium in air?

Answer Answer: The compound T2O is formed having molecular mass 22 a.m.u.

Q.23. Name the phenomenon of adsorption of hydrogen on metal surface.

Answer Answer: Occulusion.

Q.24. Which gas is used for filling airships and balloons?

Answer Answer: Since hydrogen is inflammable. A mixture of 85% He and 15% H2 is used in filling of airships and balloons.

Q.25. Give one example of zeolite used in softening of hard water.

Answer Answer: Hydrated sodium aluminium silicate,
Na2Al2Si2O8. xH2O

Q.26. Ionic hydrides are generally used to remove traces of water from organic compounds, why?

Answer Answer: Ionic hydrides give H ions which react with H2O to give H2 gas.
Na+ H H2O → NaOH + H2
Therefore, Ionic hydrides are used to remove traces of water from organic compounds.

Q.27. What is the importance of deuterium in organic reactions?

Answer Answer: Heavy hydrogen, deuterium (D) is used as a tracer to study the mechanism of organic reactions.

Q.28. What is the use of hydrogen in the manufacture of vanaspati ghee?

Answer Answer: H2 is used as reducing agent to convert vegetable oil into vegetable ghee.

Q.29. Which type of elements form interstitial (metallic) hydrides?

Answer Answer: d- and f-block elements.

Q.30. Explain why dihedral angle (111.5°) of H2O2 reduces to 90.2° in the solid state?

Answer Answer: The dihedral angle (111.5°) reduces to 90.2° in hydrogen peroxide crystal due to hydrogen bonding. The H2O2 has a non-planar structure.

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