sblock Elements - Result Question 29

####39. The pair(s) of reagents that yield paramagnetic species is/are

(a) Na and excess of NH3

(b) K and excess of O2

(c) Cu and dilute HNO3

(d) O2 and 2-ethylanthraquinol

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Answer:

Correct Answer: 39. (a,b,c)

Solution:

  1. PLAN Paramagnetic character of species can be easily explained on the basis of presence of unpaired electrons, i.e. compounds containing unpaired electron(s) is/are paramagnetic.

Reaction of alkali metals with ammonia depends upon the physical state of ammonia whether it is in gaseous state or liquid state. If ammonia is considered as a gas then reaction will be

(a) Na+NH3 (Excess) NaNH2+12H2

( NaNH2+1/2H2 are diamagnetic)

If ammonia is considered as a liquid then reaction will be

M+(x+y)NH3[M(NH3)x]++[e(NH3)y]

(b) K+O2 (Excess) KO2(K+,O2) Potassium superoxide  paramagnetic

(c) 3Cu+8HNO33Cu(NO3)2 Paramagnetic +2NO Paramagnetic +4H2O

(d)

Hence, option (a), (b) and (c) are correct choices.



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