Coordination Compounds · Question 22

JEE Main 2026 (Online) 24th January Evening ShiftNumericalMedium📈 Topic in 13% papers+4

A chromium complex with a formula CrCl3 6H2O has a spin only magnetic moment value of 3.87 BM and its solution conductivity corresponds to 1 : 2 electrolyte. 2.75 g of the complex solution was initially passed through a cation exchanger. The solution obtained after the process was reacted with excess of AgNO3. The amount of AgCl formed in the above process is g. (Nearest integer) [Given: Molar mass in g mol-1 Cr : 52, Cl : 35.5, Ag : 108, O : 16, H : 1]

Answer

Solution

= 3.87 BM = n(n+2) ⇒ n = 3 unpaired electrons ( Cr3+, 3d3).

A 1 : 2 electrolyte ⇒ two Cl- are outside the coordination sphere:

[Cr(H2O)5Cl]Cl2 H2O [Cr(H2O)5Cl]2+ + 2Cl-

The cation exchanger holds the complex cation (releasing H+); the two ionisable Cl- per formula unit pass into the solution and are precipitated by AgNO3.

Molar mass of CrCl3 6H2O = 52 + 3(35.5) + 6(18) = 266.5 g mol-1

Moles of complex = 2.75266.5 = 1.032 10-2 mol

⇒ Moles of AgCl = 2 1.032 10-2 = 2.064 10-2 mol

∴ Mass of AgCl = 2.064 10-2 143.5 = 2.96 g 3 g

Answer: 3

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