Three moles of AgCl get precipitated when one mole of an octahedral co-ordination compound with empirical formula \(CrCl_3 \cdot 3NH_3 \cdot 3H_2O\) reacts with excess of silver nitrate. The number of chloride ions satisfying the secondary valency of the metal ion is ________.
Show Hint
The number of moles of \(AgCl\) precipitated directly tells you how many chlorides are not ligands. Subtract this from the total chlorides in the formula to find the number of chloride ligands.
Step 1: Understanding the Concept:
According to Werner's theory, the primary valency is ionizable (satisfied by ions outside brackets), and the secondary valency is non-ionizable (satisfied by ligands inside brackets).
Precipitation with \(AgNO_3\) identifies the ionizable chloride ions. Step 2: Key Formula or Approach:
1. Secondary valency for an octahedral compound is 6.
2. Number of moles of AgCl = Number of chloride ions outside the coordination sphere. Step 3: Detailed Explanation:
1. Analyze the Precipitation:
3 moles of AgCl are formed per mole of compound. This means all 3 chloride (\(Cl^{-}\)) ions are outside the coordination sphere.
2. Determine the Coordination Sphere:
Empirical formula: \(CrCl_3 \cdot 3NH_3 \cdot 3H_2O\).
If 3 \(Cl\) are outside, the ligands inside must be the remaining 3 \(NH_3\) and 3 \(H_2O\) molecules.
Structural Formula: \([Cr(NH_3)_3(H_2O)_3]Cl_3\).
The total coordination number is \(3 + 3 = 6\), which matches the octahedral geometry.
3. Conclusion:
All chloride ions are ionizable and satisfy primary valency. No chloride ion is inside the brackets satisfying secondary valency. Step 4: Final Answer:
The number of chloride ions satisfying the secondary valency is 0.
