Correct Answer: 3

Explanation

Spin only magnetic moment 3.87 BM corresponds to three unpaired electrons, indicating Cr(III) with d³ configuration.

Given that the complex behaves as a 1 : 2 electrolyte, its structure must be:

[Cr(H₂O)₄Cl₂]Cl·2H₂O

This gives one chloride ion outside the coordination sphere.

Molar mass of the complex:

Cr = 52 Cl₃ = 3 × 35.5 = 106.5 6H₂O = 6 × 18 = 108

Total molar mass = 52 + 106.5 + 108 = 266.5 g mol⁻¹

Moles of complex taken:

2.75 / 266.5 ≈ 0.0103 mol

When passed through cation exchanger, the complex cation is removed and free Cl⁻ ions remain in solution.

Each mole of complex releases 3 moles of Cl⁻ ions.

Total moles of Cl⁻:

0.0103 × 3 ≈ 0.0309 mol

These react with AgNO₃ to form AgCl:

Ag⁺ + Cl⁻ → AgCl(s)

Molar mass of AgCl:

AgCl = 108 + 35.5 = 143.5 g mol⁻¹

Mass of AgCl formed:

0.0309 × 143.5 ≈ 4.43 g

Nearest integer value:

= 3 g

Hence, the required amount of AgCl is 3 g.

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