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Classify the following hydrides into covalent, ionic and interstitial hydrides.

NH3, ZrH2, CaH2, NaH, B2H6

Covalent = NH3 B2H6

Ionic = NaH, CaH2

Interstitial = ZrH2.


How is H2O2 manufactured?

Industrially H2O2 is prepared by the auto oxidation of 2 hydroxy anthraquinols. It involves a cycle of reactions. The net reaction is to catalyst union of H2 and O2 to yield H2O2

It is concentrated by careful distillation under low pressure.


What is the use of Zeolite / per mutit?

Zeolite or permutit is a sodium aluminium silicate. Na Al SiO4.3H2O. When hard water, which contains Ca2+ / Mg2+ ions, is passed through Zeolite / permutit, Na+ ion in the silicate gets exchanged for Ca+ / Mg2+ in hard water. Thus hard water is softened.


What is meant by 100-volume of Hydrogen peroxide?

Each milliliter of 100-volume H2O2 will liberate 100 volumes of oxygen at STP. It may be 30% solution H2O2.


Give examples for electron deficient, electron-precise and electron rich molecular hydrides.

Electron deficient: B2H6 (has less number of electrons to write Lewis structure)
Electron – precise: CH4
Electron – rich: NH3 and H2O (N and O have lone pairs of electrons).


Why HF, H2O and NH3 have higher boiling points, and aggregation?

Fluorine, oxygen and nitrogen are electronegative elements: They have lone pairs of electron in HF, H2O and NH3, electron rich hydride.


2KMnO4 + 3H2SO4 + 5H2O2 → K2SO4 + 2MnSO4 + 8H2O + 5O2

KMnO4 is converted into MnSO4: Oxidation number of Mn is changed from +7 to +2 by H2O2. That is H2O2 acts as a reducing agent, giving electrons to manganese. H2O2 is changed to O2 by KMnO4. Oxidation number of oxygen in H2O2 is changed from –1 to 0 in oxygen molecule. Hence KMNO4 removes electron from oxygen of H2O2 . Hence H2O2 is oxidized by KMNO4 to H2O.

2PbS(s) + H2O2 
 PbSO4(s) + 4H2O (l)

S2- in PbS is oxidized to SO4; oxidation number of S in Pbs (-2) changed to (+6) in PbSO4. Electrons are removed from Pbs by H2O2 to convert PbS to PbSO4. Hence H2O2 is an oxidizing agent.

H2O2 is converted into H2O : Oxidation number (-1) in H2O2 is changed into (-2) in H2O. Hence H2O2 is reduced by PbS.


How is H2O2 concentrated?

Aqueous H2O2 solutions spontaneously decompose to give H2O and O2. Hence 1% H2O2, formed during preparation cannot be concentrated by distillation under atmospheric pressure. Hence H2O2 solution is concentrated to 30% by distillation under reduced pressure. This further concentrated to 85% by careful distillation under low pressure. The remaining water is frozen out to give pure H2O2.


What is nascent hydrogen? How is its reactivity?

The hydrogen at the time of its production (new born) is much more reactive and is called nascent hydrogen. It is in a atomic state at the moment of its formation.

E.g. H2 molecule does not reduce KMnO4. But, Zn and HCl reduces KMnO4. Decolourise KMnO4 .

Zn + H2SO4
ZnSO4 + 2(H); – 2KMnO4 + 3H2SO4 + 10H K2SO4 + 2MnSO4 + 8H2O


What is the reaction involved using H2O2 for renovating old painting?

Old paintings rendered black PbS by the atmospheric H2S. Black PbS in painting is oxidized by H2O2 to white PbSO4

 H2O + (O)

PbS + 4(O)  PbSO4

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