Q22 of 35 Page 1

Consider the standard electrode potential values (M2+ / M) of the elements of the first transition series.


Explain:


(i) Eo value for copper is positive.


(ii) Eo value of Mn is more negative as expected from the trend.


(iii) Cr2+ is a stronger reducing agent than Fe2+

(i) Eo value of Cu is positive due to the fat that the sum of sublimation enthalpy an ionization enthalpy to convert Cu(s) to Cu2+ (aq) is so high that it is not balanced by its hydration enthalpy.


(ii) Eo value of Mn is more negative than expected value is due to the fact that after removal of electrons from 4s orbital, Mn2+ has d5 configuration which is a stable half-filled configuration.


(iii) d4 to d5 occurs in case of Cr2+ to Cr3+. It has means it has more stable t32g (half filled) whereas the configuration changes from d6 to d5 in case of Fe2+ to Fe3+.


Thus, Cr2+ is a stronger reducing agent than Fe2+


More from this chapter

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21

A metal ion Mn+ having d4 valence electronic configuration combines with three bidentate ligands to form a complex compound. Assuming Δ0 > P:

(i) Write the electronic configuration of d4 ion.


(ii) What type of hybridisation will Mn+ ion has?


(iii) Name the type of isomerism exhibited by this complex.

 22

The magnetic moments of few transition metal ions are given below:























Metal ion



Magnetic moment(BM)



Sc3+



0.00



Cr2+



4.90



Ni2+



2.84



Ti3+



1.73



(at no. Sc = 21, Ti =22, Cr = 24, Ni = 28)


Which of the given metal ions :


(i) has the maximum number of unpaired electrons?


(ii) forms colourless aqueous solution?


(iii) exhibits the most stable +3 oxidation state?

 23

Ashwin observed that his friend Shubham was staying aloof, not playing with friends and becoming easily irritable for some weeks. Ashwin told his teacher about this, who, in turn, called Shubham’s parents and advised them to consult a doctor. Doctor after examining Shubham prescribed antidepressant drugs for him.

After reading the above passage, answer the following questions:


(i) Name two antidepressant drugs.


(ii) Mention the values shown by Ashwin.


(iii) How should Shubham’s family help him other than providing medicine?


(iv) What is the scientific explanation for the feeling of depression?

 24

Arrange the following in the order of property indicated against each set:

(i) F2, Cl2, Br2, I2 (increasing bond dissociation enthalpy)


(ii) H2O, H2S, H2Se, H2Te (increasing acidic character)


(b) A colourless gas ‘A’ with a pungent odour is highly soluble in water and its aqueous solution is weakly basic. As a weak base it precipitates the hydroxides of many metals from their salt solution. Gas ‘A’ finds application in detection of metal ions. It gives a deep blue colouration with copper ions. Identify the gas ‘A’ and write the chemical equations involved in the following:


(i) Gas ‘A’ with copper ions


(ii) Solution of gas ‘A’ with ZnSO4 solution.