Yes, cobalt can displace zinc in a chemical reaction. This occurs because cobalt is more reactive than zinc, allowing it to take the place of zinc in its compounds.
Understanding Metal Displacement Reactions
A metal displacement reaction is a fundamental chemical process where a more reactive metal replaces a less reactive metal from its compound. These reactions typically happen when a free, more reactive metal is introduced into a solution containing ions of a less reactive metal. The driving force behind these reactions is the difference in the metals' electrochemical potential or their position in the reactivity series.
Cobalt's Reactivity: Why It Displaces Zinc
Cobalt is a transition metal known for its strength and moderate melting point of 1495 °C. More importantly, its chemical reactivity places it higher than zinc in the electrochemical or reactivity series. This higher reactivity means that cobalt has a greater tendency to lose electrons and form positive ions compared to zinc.
When cobalt metal is introduced into a compound containing zinc ions (for example, zinc sulfate solution), the cobalt atoms will readily give up their electrons to form cobalt ions, while the zinc ions in the solution will accept these electrons to become neutral zinc metal. This results in the deposition of zinc metal and the formation of a cobalt compound.
The Reactivity Series
The reactivity series (also known as the activity series) is a list of metals arranged in order of their decreasing reactivity. Metals higher on the list are more reactive and can displace metals lower on the list from their compounds.
| Metal | Symbol | Reactivity (Decreasing) |
|---|---|---|
| Cobalt | Co | Higher |
| Nickel | Ni | Moderate |
| Zinc | Zn | Lower |
As shown in the table, cobalt is positioned above zinc in terms of reactivity. It is also more reactive than nickel, indicating its ability to displace both zinc and nickel from their respective compounds. For a more comprehensive look at the reactivity series, you can refer to resources on metal activity series.
How Cobalt Displaces Zinc
The displacement reaction can be represented by a general chemical equation:
Co(s) + ZnX(aq) → CoX(aq) + Zn(s)
Where:
Co(s)represents solid cobalt metal.ZnX(aq)represents a zinc compound dissolved in water (e.g., zinc sulfate,ZnSO₄).CoX(aq)represents the newly formed cobalt compound dissolved in water (e.g., cobalt sulfate,CoSO₄).Zn(s)represents solid zinc metal that precipitates out of the solution.
Example:
If a piece of cobalt metal is placed into a solution of zinc sulfate, the following reaction occurs:
Co(s) + ZnSO₄(aq) → CoSO₄(aq) + Zn(s)
In this reaction:
- Cobalt atoms (Co) lose two electrons to become cobalt ions (Co²⁺).
- Zinc ions (Zn²⁺) from the zinc sulfate solution gain two electrons to become zinc atoms (Zn), which then deposit as solid zinc metal.
This process demonstrates cobalt's greater chemical activity compared to zinc.
Practical Implications
The ability of one metal to displace another has several practical applications:
- Corrosion Prevention: Understanding metal reactivity is crucial in designing anti-corrosion strategies, such as sacrificial anodes, where a more reactive metal is used to protect a less reactive one.
- Metallurgy: Displacement reactions are utilized in the extraction and purification of metals from their ores.
- Electrochemical Cells: The principles of reactivity are fundamental to how batteries and other electrochemical devices function.
- Chemical Synthesis: In laboratory and industrial settings, these reactions are used to synthesize new compounds or recover metals.
Key Takeaways
- Cobalt is more reactive than zinc.
- When cobalt is introduced into a zinc compound, it will displace zinc from that compound.
- This is a classic example of a single displacement reaction governed by the metals' positions in the reactivity series.
