Question

3a. which is more reactive with iron ions? water chloride
3b. which is more reactive with iron ions? chloride thiocyanate
3c. which is more reactive with iron ions? thiocyanate hydroxide
3d. which is more reactive with iron ions? chloride hydroxide

Explanation:

Step1: Recall Reactivity Series

The reactivity of ligands with metal ions (here Iron ions) can be compared based on their ability to form stable complexes. Hydroxide (\(OH^-\)) forms very stable complexes with Iron ions. Thiocyanate (\(SCN^-\)) also forms stable complexes but less stable than hydroxide. Chloride (\(Cl^-\)) forms relatively less stable complexes compared to hydroxide and thiocyanate. Water (\(H_2O\)) forms the least stable complexes among these as it is a weak field ligand.

Step2: Compare Each Pair

• 3a: Chloride (\(Cl^-\)) is more reactive than water (\(H_2O\)) with Iron ions as \(Cl^-\) is a stronger field ligand than \(H_2O\).
• 3b: Thiocyanate (\(SCN^-\)) is more reactive than chloride (\(Cl^-\)) with Iron ions. \(SCN^-\) can form more stable complexes (due to its ability to act as a better electron - donor and form coordinate bonds more effectively in some cases compared to \(Cl^-\) for Iron ions).
• 3c: Hydroxide (\(OH^-\)) is more reactive than thiocyanate (\(SCN^-\)) with Iron ions. \(OH^-\) forms very stable metal - hydroxide complexes (e.g., \(Fe(OH)_3\) is a well - known stable compound) due to strong electrostatic and covalent interactions in the complex.
• 3d: Hydroxide (\(OH^-\)) is more reactive than chloride (\(Cl^-\)) with Iron ions. \(OH^-\) forms more stable complexes (e.g., \(Fe(OH)_3\) vs. \(FeCl_3\), \(Fe(OH)_3\) has lower solubility in many cases indicating a more stable complex)

Answer:

3a. Chloride
3b. Thiocyanate
3c. Hydroxide
3d. Hydroxide