The metal cadmium tends to form Cd²⁺ ions. The following observations are made: (i) When a strip of zinc metal is placed in CdCl₂(aq), cadmium metal is deposited on the strip. (ii) When a strip of cadmium metal is placed in Ni(NO₃)(aq), nickel metal is deposited on the strip. (a) Write net ionic equations to explain each of the preceding observations.

Verified step by step guidance

1. Step 1: Understand the concept of net ionic equations. These equations show only the species that actually change during the reaction, omitting spectator ions.
2. Step 2: For observation (i), identify the reactants and products. Zinc metal (Zn) is placed in cadmium chloride solution (CdCl2). Cadmium metal (Cd) is deposited, indicating a redox reaction where zinc is oxidized and cadmium is reduced.
3. Step 3: Write the half-reactions for observation (i). Zinc is oxidized: Zn → Zn²⁺ + 2e^-. Cadmium is reduced: Cd²⁺ + 2e^- → Cd.
4. Step 4: Combine the half-reactions for observation (i) to form the net ionic equation: Zn + Cd²⁺ → Zn²⁺ + Cd.
5. Step 5: For observation (ii), identify the reactants and products. Cadmium metal (Cd) is placed in nickel nitrate solution (Ni(NO₃)₂). Nickel metal (Ni) is deposited, indicating a redox reaction where cadmium is oxidized and nickel is reduced. Write the net ionic equation: Cd + Ni²⁺ → Cd²⁺ + Ni.

Key Concepts

Redox Reactions

Redox reactions involve the transfer of electrons between species, leading to changes in oxidation states. In the context of the question, cadmium (Cd) is reduced from Cd^2+ to Cd metal, while zinc (Zn) is oxidized from Zn metal to Zn^2+. Understanding these electron transfers is crucial for writing the net ionic equations for the reactions observed.

Ionic Equations

Ionic equations represent the species involved in a chemical reaction in their ionic forms. In this case, the net ionic equations will show only the ions and molecules that participate in the reaction, excluding spectator ions. This simplification helps clarify the actual chemical changes occurring during the reactions with cadmium and zinc.

Electrochemical Series

The electrochemical series ranks elements based on their standard electrode potentials, indicating their tendency to be oxidized or reduced. Zinc has a higher tendency to oxidize compared to cadmium, which explains why it can reduce Cd^2+ to Cd metal. Understanding this series is essential for predicting the outcomes of the metal displacement reactions described in the question.