Question

When a coordination compound CrCl₃​⋅6H₂​O is mixed with AgNO₃​, 2 moles of AgCl are precipitated per mole of the compound. Write: (i) Structural formula of the complex. (ii) IUPAC name of the complex.

a. (i) [Cr(H₂​O)₆​]Cl₃​, (ii) Hexaaquachromium(III) chloride
b. (i) [Cr(H₂O)₃​]Cl₃​, (ii) Tris(aquachromium(III)) chloride
c. (i) [Cr(H₂O)₄​]Cl₂​, (ii) Tetra(aquachromium(II)) chloride
d. (i) [Cr(H₂​O)₂​]Cl₄​, (ii) Dihydra(aquachromium(IV)) chloride

Answer 1

The complex in question is [Cr(H2O)6]Cl3 due to the precipitation of 2 moles of AgCl per mole of the complex, indicating two reactive chloride ions. The corresponding IUPAC name is hexaaquachromium(III) chloride. Therefore, the correct answer is 'a' according to the given options.

Step-by-step explanation:

When CrCl3·6H2O is mixed with AgNO3, the precipitation of 2 moles of AgCl per mole of the compound indicates that there are 2 moles of chloride ions that are free to react with the silver ions from AgNO3. This suggests that the structure of the complex has chromium surrounded by six water molecules in an octahedral configuration, with three chloride ions as counter ions outside the coordination sphere.

The structural formula of the complex is then [Cr(H2O)6]Cl3, where the chromium is in a +3 oxidation state. Following the IUPAC nomenclature for naming coordination compounds, the IUPAC name of the complex is hexaaquachromium(III) chloride.