Question

Yellow compound of lead chromate gets dissolved on treatment with hot NaOH solution. The product of lead formed is a:

• A. Tetraanionic complex with coordination number six
• B. Neutral complex with coordination number four
• C. Dianionic complex with coordination number six
• D. Dianionic complex with coordination number four

Answer 1

The Correct Option is D

The question concerns the reaction of yellow lead chromate with hot NaOH solution, yielding a lead complex. The solution proceeds step-by-step to identify the correct product.

Lead chromate (\( \text{PbCrO}_4 \)) is a yellow compound used in paints and pigments. It reacts with hot sodium hydroxide (\( \text{NaOH} \)) solution to form a lead complex. The provided options describe various types of complexes.

Reaction analysis:

1. Dissolving \( \text{PbCrO}_4 \) in \( \text{NaOH} \) produces \( \text{Pb(OH)}_4^{2-} \), a lead complex.
2. In this complex, lead ions (\( \text{Pb}^{2+} \)) coordinate with hydroxide ions (\( \text{OH}^- \)) to form \( \text{Pb(OH)}_4^{2-} \).
3. The complex is dianionic, carrying a -2 charge.
4. The lead atom is bonded to four hydroxide ions, resulting in a coordination number of four.

Comparison of the identified complex \( \text{Pb(OH)}_4^{2-} \) with the options:

• Option 1, "Tetraanionic complex with coordination number six," is incorrect due to the complex being dianionic with a coordination number of four, not tetraanionic or six.
• Option 2, "Neutral complex with coordination number four," is incorrect as the complex is not neutral but has a -2 charge.
• Option 4, "Dianionic complex with coordination number four," is correct, accurately describing \( \text{Pb(OH)}_4^{2-} \).
• Option 3, "Dianionic complex with coordination number six," is incorrect because the coordination number is four.

The correct answer is: Dianionic complex with coordination number four.

This explanation demonstrates the application of basic coordination chemistry and complex ion formation principles to problem-solving.