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CBSE 12th Standard Chemistry Subject The p-Block Elements Ncert Exemplar 2 Mark Questions 2021

Published on: 25/05/2021

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Std: 12th Standard CBSE - Chemistry

chapter: - NCERT Exemplers

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Questions:

Generic 2

5 x 2 = 10

Write the structure of pyrophosphoric acid.

Write a balanced chemical equation for the reaction showing catalytic oxidation of NH₃ by atmospheric oxygen.

Explain why the stability of oxoacids of chlorine increases in the order given below:
HCIO< HCIO₂ < HCIO₃ < HCIO₄

Assign a reason for each of the following statements:
(i) More metal fluorides are ionic in nature than metal chlorides.
(ii) SCI₆ is not known but SF₆ is known.

State reasons for each of the following:
(i) All the P-Cl bonds in PCl₅ molecule are not equivalent.
(ii) Sulphur has greater tendency for catenation than oxygen.

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Answers Key:

Generic 2

5 x 2 = 10

\(HO-\overset { \underset { \parallel }{ O } }{ \underset { \overset { | }{ HO } }{ P } } -O-\overset { \underset { \parallel }{ O } }{ \underset { \overset { | }{ OH } }{ P } } -OH\) Pyrophosphoric \(\left( { H }_{ 4 }{ P }_{ 2 }{ O }_{ 7 } \right) \) acid

\(4{ NH }_{ 3 }+5{ O }_{ 2 }\xrightarrow [ 500K,9bar ]{ Pt/Rh\ gauze,catalyst } 4NO+6{ H }_{ 2 }O\)

It is due to stability oxo anions follows the following order due to dispersal of charge on more number of electronegative oxygen atoms.
CIO^-< CIO₂^- < CIO₃^- < CIO₄^-

(i) It is due to greater difference in electronegativity in fluorides than in chlorides.
(ii) In SCI₆ there is more repulsion than in SF₆, therefore, SCI₆ does not exist.

(i) it is because all the bonds are not in same plane. Axial bonds are longer than equatorial bonds due to more repulsion.
(ii) It is because of strong S-S bond than O-O due to greater repulsion between valence electrons of smaller atoms of oxygen than sulphur atoms.