Question

When zinc is kept in ${\mathrm{CuSO}}_4$ solution copper gets precipitated because (1) Standard reduction potential of zinc is more than copper (2) Standard reduction potential of zinc is less than copper (3) Atomic number of zinc is larger than copper (4) Atomic number of zinc is lower than copper

Short answer

Option (2) Standard reduction potential of zinc is less than copper.

Step-by-step solution

Identify Key Concept

Understand that the reaction involves the replacement of copper ions by zinc atoms in a ${\text{CuSO}}_4$ solution. This relies on the standard reduction potentials of the metals involved.

Check Standard Reduction Potentials

Look up the standard reduction potentials for zinc ${\text{Zn}}^{2+}/\text{Zn}$ and copper ${\text{Cu}}^{2+}/\text{Cu}$. The standard reduction potential of zinc is $-0.76\text{V}$ and that of copper is $+0.34\text{V}$.

Compare Reduction Potentials

Compare the values obtained: Zinc has a lower reduction potential $-0.76\text{V}$ than copper $+0.34\text{V}$.

Determine Outcome

Since zinc has a lower standard reduction potential, it is more easily oxidized than copper. Therefore, zinc can displace copper from the solution, leading to the precipitation of copper.

Select the Correct Answer

Based on the comparison, the correct answer is (2) Standard reduction potential of zinc is less than copper.

Key concepts

Electrochemistry

Electrochemistry is a branch of chemistry that studies the relationship between electricity and chemical reactions. This field is essential because it explains how batteries work, how metals corrode, and much more.
At its core, electrochemistry deals with the movement of electrons between different chemical species. When electrons move, chemical reactions happen. These reactions can either release energy, as in batteries, or require energy, as in electroplating.
A key concept in electrochemistry is the electrochemical cell. There are two types of cells: galvanic (or voltaic) cells and electrolytic cells. Galvanic cells generate electric current from spontaneous chemical reactions, whereas electrolytic cells drive non-spontaneous reactions using electric current.
Standard reduction potential (SRP) is another crucial idea. It measures the tendency of a chemical species to gain electrons and get reduced. Higher SRP means a greater tendency to accept electrons. We use SRP values to predict the direction of redox reactions and their feasibility.

Oxidation-Reduction Reactions

Oxidation-Reduction reactions, also known as redox reactions, involve the transfer of electrons between two species. These reactions are fundamental in many biological processes, industrial applications, and of course, electrochemistry.
In a redox reaction:

• Oxidation is the loss of electrons.
• Reduction is the gain of electrons.

For example, in the reaction where zinc displaces copper from \text{CuSO}_{4} solution, zinc loses electrons (oxidizes), and copper gains electrons (reduces).
The standard reduction potential plays a critical role in these reactions. A species with higher SRP will likely get reduced, while one with lower SRP tends to get oxidized.
In our original exercise, zinc has a lower SRP ${\text{Zn}}^{2+}/\text{Zn}:-0.76\text{V}$ compared to copper ${\text{Cu}}^{2+}/\text{Cu}:+0.34\text{V}$. Hence, zinc oxidizes, displacing copper from the solution.

Metal Displacement Reactions

Metal displacement reactions are a type of redox reaction wherein a more reactive metal displaces a less reactive metal from its compound. This principle is based on the standard reduction potential of the metals involved.
In these reactions:

• The more reactive metal gets oxidized (loses electrons).
• The less reactive metal gets reduced (gains electrons), often precipitating out as a solid.

For instance, in the original exercise, zinc is placed in a copper sulfate ${\text{CuSO}}_4$ solution. Zinc has a lower SRP $-0.76\text{V}$ than copper $+0.34\text{V}$, meaning zinc is more likely to be oxidized.
As zinc gets oxidized, it releases electrons, which are then taken up by the copper ions in the solution, forming solid copper. This reaction demonstrates the displacement of copper by zinc, perfectly exemplifying a metal displacement reaction.