Question

Addition of zinc powder to copper sulphate solution precipitates copper due to (1) Reduetion of \(\mathrm{Cu}^{2+}\) (2) Reduction of \(\mathrm{SO}_{4}^{2-}\) (3) Reduction of \(\mathrm{Zn}^{2+}\) (4) Hydrolysis of \(\mathrm{CuSO}_{4}\)

Short answer

Reduction of \( \text{Cu}^{2+} \).

Step-by-step solution

- Understanding the Reaction

When zinc is added to a copper sulfate solution \(\text{CuSO}_4 \), a reaction occurs between zinc \(\text{Zn} \) and copper ions \(\text{Cu}^{2+} \). The reactants and products can be identified to understand the changes.

- Identifying the Reactants and Products

The reactants are zinc powder \( \text{Zn} \) and copper sulfate \( \text{CuSO}_4 \), which dissociates into \( \text{Cu}^{2+} \) and \( \text{SO}_{4}^{2-} \) ions in an aqueous solution.

- Writing the Balanced Chemical Equation

The balanced chemical equation for this reaction is: \[ \text{Zn} + \text{CuSO}_4 \rightarrow \text{ZnSO}_4 + \text{Cu} \] Here, zinc displaces copper from copper sulfate solution.

- Identifying the Redox Reaction

In the balanced equation, Zn is oxidized (loses electrons) to \( \text{Zn}^{2+} \) and \( \text{Cu}^{2+} \) is reduced (gains electrons) to \( \text{Cu} \). This process is called a redox reaction.

- Determining the Correct Answer

Since \( \text{Cu}^{2+} \) is gaining electrons and being reduced to copper metal, the correct answer is: (1) Reduction of \( \text{Cu}^{2+} \).

Key concepts

copper sulfate reaction

When zinc powder is added to a copper sulfate solution, a chemical reaction occurs. This reaction involves the substances zinc \(\text{Zn} \) and copper sulfate \(\text{CuSO}_4 \). In an aqueous solution, copper sulfate dissociates into copper ions \(\text{Cu}^{2+} \) and sulfate ions \(\text{SO}_{4}^{2-} \).The overall reaction can be represented by the balanced chemical equation: \[ \text{Zn} + \text{CuSO}_4 \rightarrow \text{ZnSO}_4 + \text{Cu} \]This means zinc reacts with copper sulfate to form zinc sulfate \(\text{ZnSO}_4 \) and copper metal \(\text{Cu} \).The reaction is significant in studying chemical changes and involves the exchange of ions and elements between the reactants and products.

zinc reduction

In the reaction between zinc and copper sulfate, zinc plays a crucial role. When zinc powder is added to the solution, it undergoes oxidation. This means that zinc loses electrons and is transformed into zinc ions: \[ \text{Zn} \rightarrow \text{Zn}^{2+} + 2e^- \]As zinc loses electrons, it frees up electrons that are then gained by the copper ions. This is the process where copper ions \(\text{Cu}^{2+} \) are reduced.This swapping of electrons defines this reaction as an oxidation-reduction (redox) process where one substance loses electrons (oxidation) and another gains electrons (reduction).It's important to note that the element undergoing reduction (copper ions gaining electrons) directly depends on the oxidation of another element (zinc losing electrons).

oxidation-reduction process

The reaction between zinc and copper sulfate is a classic example of an oxidation-reduction (redox) process. In a redox reaction, two simultaneous processes happen: one element is oxidized while the other is reduced. Let's break it down:

• **Oxidation**: Involves the loss of electrons. Here, zinc \(\text{Zn} \) loses two electrons to become zinc ions \(\text{Zn}^{2+} \).
• **Reduction**: Involves the gain of electrons. Copper ions \(\text{Cu}^{2+} \) gain those two electrons to become copper metal \(\text{Cu} \).

When we combine the oxidation and reduction half-reactions, we get the complete redox reaction: \[ \text{Zn} + \text{Cu}^{2+} \rightarrow \text{Zn}^{2+} + \text{Cu} \]Here, zinc is the reducing agent because it donates electrons and facilitates the reduction of copper ions. Conversely, copper ions are the oxidizing agent because they accept electrons from zinc.This concept is fundamental in understanding many chemical processes, such as metabolism in biology, corrosion in materials science, and energy production in electrochemistry.