Problem 169 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is/are correct regarding the electrolytic preparation of \(\mathrm{H}_{2} \mathrm{O}_{2} ?\) (a) sulphuric acid undergoes oxidation (b) hydrogen is liberated at anode (c) \(50 \% \mathrm{H}_{2} \mathrm{SO}_{4}\) is used (d) lead is used as cathode

Step-by-Step Solution

Answer

(c) and (d) are correct.

Step 1: Understanding the Electrolytic Process

Electrolysis involves using an electric current to drive a non-spontaneous chemical reaction. For the preparation of hydrogen peroxide (\( H_2O_2 \)), specific substances undergo reactions at the electrodes.

Step 2: Analyze the Oxidation Reaction with Sulfuric Acid

Sulfuric acid (\( H_2SO_4 \)) is commonly involved in the preparation of \( H_2O_2 \) through an electrolytic process. Determine whether it undergoes oxidation at the anode. During electrolysis, \( H_2SO_4 \) can undergo reactions that lead to peroxide ion formation, but it is not oxidized directly in this context. Thus, option (a) is not correct.

Step 3: Evaluate Gas Liberation at the Anode

Check if hydrogen is liberated at the anode. In electrolysis, the anode usually sees oxidation. Hydrogen gas is typically produced at the cathode, not the anode. Hence, option (b) is incorrect.

Step 4: Determine the Concentration of Sulfuric Acid

The concentration of sulfuric acid is crucial in the electrolytic preparation of \( H_2O_2 \). Typically, a 50% sulfuric acid solution is used. Therefore, option (c) is correct.

Step 5: Examine the Material Used for Cathode

Identify the appropriate material for the cathode in this process. Lead is often used due to its chemical resistance and conductivity. Thus, option (d) is correct.

Key Concepts

Electrolysis

Electrolysis is a fascinating process used to cause a chemical reaction through the application of electric current. This is especially handy when the chemical process is not spontaneous. Essentially, the procedure involves taking an electrolyte—an electrically conductive liquid—and splitting it up using electricity.

• An electrolyte is typically a substance that produces an electrically conducting solution when dissolved in a polar solvent like water.
• In electrolysis, this solution is subjected to an electric current, causing its decomposition.
• This process leads to different reactions happening at the cathode and anode (the two electrodes placed in the solution).

The overall goal here is to use electricity to induce a reaction that wouldn't naturally occur on its own. In the case of preparing hydrogen peroxide (\( H_2O_2 \)) through electrolysis, specific reactions occur that are orchestrated by the setup, paving the way for the formation of desired products.

Sulfuric Acid

Sulfuric acid, with the chemical formula \( H_2SO_4 \), plays a critical role in the electrolytic production of hydrogen peroxide. Its ability to conduct electricity while participating in specific electrode reactions makes it invaluable in this context.

• This strong acid is often diluted to a 50% concentration for the process we are discussing.
• While sulfuric acid handles essential tasks in decomposing and forming components, it doesn’t undergo direct oxidation in this setup.
• Instead, it assists in creating the right environment for peroxide ion formation.

Sulfuric acid’s properties, such as high conductivity and stability as a compound, enable effective management of the electric charge needed to initiate reactions at the electrodes during electrolysis. Its essentially supporting role is all about enabling reactions by maintaining the right electrolytic conditions.

Electrode Reactions

In the electrolytic configuration for making hydrogen peroxide, understanding what happens at each electrode, cathode and anode, is crucial. These reactions dictate the products formed and their efficiency.

• The anode is where oxidation generally occurs; however, hydrogen gas formation typically happens at the cathode.
• In this particular setup, lead is chosen as the cathode material due to its effective conductivity and resistance to corrosion from sulfuric acid.
• This choice ensures that no unwanted side reactions compromise the electrolytic process.

These electrode reactions during the electrolysis are precisely what allows the transformation of raw materials into useful compounds like hydrogen peroxide. Watching the interaction of electricity and chemistry is truly remarkable, as each part has its role and importance in the successful production process.