Consider a mixture X made by dissolving cobalt ammine complexes reacting with AgNO3 and BaCl2 find correct statement
Q. Consider a mixture ' X ' which is made by dissolving 0.4 mol of [Co(NH₃)₅SO₄]Br and 0.4 mol of [Co(NH₃)₅Br]SO₄ in water to make 4 L of solution. When 2 L of mixture ' X ' is allowed to react with excess of AgNO₃, it forms precipitate ' Y '. The rest 2 L of mixture ' X ' reacts with excess BaCl₂ to form precipitate ' Z '. Which of the following statements is CORRECT?

(A) 0.1 mol of ' Y ' is formed.

(B) 0.4 mol of ' Z ' is formed.

(C) 0.2 mol of ' Z ' is formed.

(D) ' Y ' is BaSO₄ and ' Z ' is AgBr.

Correct Answer: 0.2 mol of ' Z ' is formed.

Explanation

Total volume of solution is 4 L containing 0.4 mol of each complex. Therefore, in 2 L of solution, moles of each complex present are:

\[ \frac{2}{4} \times 0.4 = 0.2 \text{ mol each} \]

Complex [Co(NH₃)₅SO₄]Br gives SO₄²⁻ as a counter ion in solution, while in [Co(NH₃)₅Br]SO₄, SO₄²⁻ is outside the coordination sphere.

When 2 L of mixture reacts with excess BaCl₂, only free sulfate ions form precipitate of BaSO₄.

Only [Co(NH₃)₅Br]SO₄ contributes free SO₄²⁻ ions. Hence, moles of sulfate ions reacting:

\[ \text{Moles of SO₄}^{2-} = 0.2 \text{ mol} \]

Thus, moles of BaSO₄ precipitate formed:

\[ \text{Moles of Z} = 0.2 \text{ mol} \]

Hence, the correct statement is option (C).

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