Question

When FeCl₃ is added to excess of hot water gives a sol ‘X’. When FeCl₃ is added to NaOH_(aq) solution, gives sol ‘Y’.
X and Y formed in the above processes respectively are

• A. Fe₂O₃ . xH₂O / OH^- and Fe₂O₃ . xH₂O/Fe³⁺
• B. Fe₂O₃ . xH₂O / H⁺ and Fe₂O₃ . xH₂O/Na⁺
• C. Fe₂O₃ . xH₂O / Cl^- and Fe₂O₃ . xH₂O/OH^-
• D. Fe₂O₃ . xH₂O / Fe³⁺ and Fe₂O₃ . xH₂O/OH^-

Answer 1

The Correct Option is D

When FeCl₃ (ferric chloride) is added to hot water and NaOH, two different solutions are formed. Let's analyze both reactions:

Step 1: FeCl₃ added to hot water (giving sol X)

When FeCl₃ is added to hot water, it undergoes hydrolysis and forms a colloidal solution of ferric hydroxide (Fe(OH)₃) with a reddish-brown color. The reaction can be written as:

\[ \text{FeCl}_3 + 3\text{H}_2\text{O} \rightarrow \text{Fe(OH)}_3 \, \text{(colloidal)} + 3\text{HCl} \] The colloidal particles of Fe(OH)₃ are surrounded by water molecules and hydroxide ions. Therefore, sol X is represented as: \[ \text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O} / \text{OH}^- \]

Step 2: FeCl₃ added to NaOH solution (giving sol Y)

When FeCl₃ is added to NaOH solution, the iron ions react with hydroxide ions to form ferric hydroxide (Fe(OH)₃), which dissolves in excess NaOH, forming a soluble complex ion. The reaction is:

\[ \text{FeCl}_3 + 3\text{NaOH} \rightarrow \text{Fe(OH)}_3 + 3\text{NaCl} \] In excess NaOH, Fe(OH)₃ dissolves to form the soluble ferrate complex, and sol Y is represented as: \[ \text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O} / \text{Fe}^{3+} \]

Conclusion:

The correct matching of sol X and sol Y is: - Sol X: \(\text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O} / \text{OH}^-\) - Sol Y: \(\text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O} / \text{Fe}^{3+}\) Therefore, the correct answer is Option (D).

Correct Answer: Option (D)