Problem 123 - A Complete Resource Book in Chemistry for JEE Main

Question

Zinc-copper couple that can be used as a reducing agent is obtained by (a) zinc coated with copper (b) zinc and copper wires welded together (c) mixing zinc dust and copper gauze (d) copper coated with zinc

Step-by-Step Solution

Answer

(d) copper coated with zinc

Step 1: Understanding Reducing Agent

A reducing agent donates electrons and is oxidized in a chemical reaction. The zinc-copper couple is a reducing agent because it involves the use of zinc, which readily gives up electrons.

Step 2: Analyzing the Options

We need to delineate which option involves zinc effectively as the element that will donate electrons. Options like zinc coated with copper or copper coated with zinc indicate different roles for zinc.

Step 3: Examining Zinc's Role

In the reduction reaction, zinc must play a pivotal role in electron donation. Option (d), copper coated with zinc, emphasizes zinc's electron donation capability, as it is on the external surface and thus more reactive in sacrificial corrosion or reduction processes.

Key Concepts

Zinc-Copper Couple

The zinc-copper couple is a fascinating entity used as a reducing agent in chemical reactions. This couple is formed when zinc and copper are combined in such a way that zinc can effectively donate electrons to other chemical species. In a typical setup, zinc is usually present in an exposed form on the external surface, enhancing its reactivity. When it comes in contact with a reactive substance, zinc readily gives up electrons, making it an essential player in reduction reactions. Moreover, using zinc dust and copper gauze is a common method to effectively form this couple. The fine zinc particles provide a large surface area, which allows for significant electron transfer when zinc atoms lose electrons and are oxidized. This makes the zinc-copper couple a highly useful reducing agent in various chemical processes.

Chemical Reaction

A chemical reaction occurs when two or more substances interact and transform into different chemical products. In the presence of a zinc-copper couple, chemical reactions are driven by the transfer of electrons from zinc to another substance. This electron donation results in reduction, while the zinc itself undergoes oxidation. In the context of our exercise, the reaction is all about finding which arrangement of zinc and copper effectively supports electron donation by zinc. During a chemical reaction, specifically a reduction-oxidation reaction (redox reaction), one substance acts as the electron donor (in this case, zinc) and another as the electron acceptor. Identifying these roles is key to understanding how reactions proceed and predicting their products.

Electron Donation

Electron donation is a crucial process in many chemical reactions, particularly in redox reactions. An electron donor is a molecule that provides electrons to another compound, and zinc plays this role effectively when paired in a zinc-copper couple. Zinc's ability to donate electrons stems from its position on the periodic table. It has a relatively low ionization energy, meaning it does not require a lot of energy to remove its outer electrons. This makes zinc highly effective as a reducing agent. When zinc donates electrons, it transforms from a neutral atom to a positively charged ion. This electron transfer can then induce changes in other substances, typically resulting in reduction. This fundamental concept is why understanding electron donation is so essential in studying chemical reactions.