Coordination Compounds 2 Question 24

####26. On treatment of 100mL of 0.1M solution of CoCl3.6H2O with excess of AgNO3;1.2×1022 ions are precipitated. The complex is

(2017 Main)

(a) [Co(H2O)4Cl2]Cl2H2O

(b) [Co(H2O)3Cl3]3H2O

(c) [Co(H2O)6]Cl3

(d) [Co(H2O)5Cl]Cl2H2O

Show Answer

Answer:

Correct Answer: 26. (b, c)

Solution:

  1. Molarity (M)= Number of moles of solute  Volume of solution (in L) 

Number of moles of complex

= Molarity × volume ( in mL)1000 =0.1×1001000=0.01mole

Complex ion Electronic
configuration of
Num nbe
elec
paired
(n)
[Cr(H2O)6]2+ Cr2+;[Ar]3d4 1 1 1 1 ;4
[Fe(H2O)6]2+ Fe2+;[Ar]3d6 11 1 1 1 1;4
[Mn(H2O)6]2+ Mn2+;[Ar]3d5 1 1 1 1 1;5
[CoCl4]2 Co2+;[Ar]3d7 11 11 1 1 1;3

Number of moles of ions precipitate

=1.2×10226.02×1023=0.02 moles 

Number of Clpresent in ionisation sphere

= Number of moles of ions precipitated  Number of moles of complex =0.020.01=2

2Clare present outside the square brackets, i.e. in ionisation sphere. Thus, the formula of complex is

[Co(H2O)5Cl]Cl2H2O.



NCERT Chapter Video Solution

Dual Pane