Q21 of 22 Page 1

(a) Account for the following:

(i) Cu+ is unstable in an aqueous solution.


(ii) Transition metals form complex compounds.


(b) Complete the following equation:


Cr2O72- + 8H+ + 3NO2- →


(a)


(i) Many copper (I) compounds are unstable in aqueous solution and undergo disproportionation reaction. The stability of Cu2+ rather than Cu+ is due to the much more negative hydration enthalpy of Cu2+ than Cu+, which more than compensates for the second ionization enthalpy of Cu.


2Cu+ → Cu2+ + Cu


(ii) The transition metals form a large number of complex compounds. This is due to


• Comparatively smaller sizes of the metal ions,


• their high ionic charges, and


• The availability of d orbitals to accommodate lone pair of electrons donated by ligands.


(b) Cr2O72- + 8H+ + 3NO2- → 2Cr3+ + 3NO3- + 4H2O


More from this chapter

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19

Give reasons for the following:

(i) Phenol is more acidic than methanol.


(ii) The C – O – H bond angle in alcohols is slightly less than the tetrahedral angle (109°28’).


(iii) (CH3)3C – O – CH3 on reaction with HI gives (CH3)3C - I and CH3 – OH as the main products and not (CH3)3C – OH and CH3- I.


 20

Predict the products of the following reactions:

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 22

Write the names and structures of the monomers of the following polymers:

(i) Terylene


(ii) Buna-S


(iii) Neoprene


 23

Seeing the growing cases of diabetes and depression among young children, Mr. Chopra, the principal of one reputed school organized a seminar in which he invited parents and principals. They all resolved this issue by strictly banning junk food in schools and introducing healthy snacks and drinks like soup, lassi, milk, etc. in school canteens. They also decided to make compulsory half an hour of daily physical activities for the students in the morning assembly. After six months, Mr. Chopra conducted the health survey in most of the schools and discovered a tremendous improvement in the health of the students.

After reading the above passage, answer the following questions:


(i) What are the values (at least two) displayed by Mr. Chopra? (ii) As a student, how can you spread awareness about this issue? (iii) Why should antidepressant drugs not be taken without consulting a doctor? (iv) Give two examples of artificial sweeteners.