Question

Which of the following is not 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

Short answer

Option (b) is incorrect; hydrogen is not liberated at the anode.

Step-by-step solution

Analyzing Option (a)

Option (a) states that sulphuric acid undergoes oxidation. This is correct because, in the process of electrolysis of sulfuric acid to produce hydrogen peroxide, sulfuric acid does undergo a reaction that can involve oxidation.

Evaluating Option (b)

Option (b) claims hydrogen is liberated at the anode. In an electrolytic cell, hydrogen ions (or protons) typically gain electrons at the cathode to form hydrogen gas, not at the anode. Therefore, this statement is incorrect regarding the process.

Checking Option (c)

Option (c) specifies that 50% \( \mathrm{H}_{2} \mathrm{SO}_{4} \) is used. This concentration is typically used in the electrolytic preparation of hydrogen peroxide to ensure proper conductivity and product formation.

Reviewing Option (d)

Option (d) mentions that lead is used as the cathode. In the electrolysis setup, a lead electrode is often used as the cathode because it is inert under these specific conditions, preventing undesired reactions. Thus, this is correct.

Key concepts

Electrolytic preparation

Electrolytic preparation is a fascinating process used to produce certain chemicals, including hydrogen peroxide. It involves passing an electric current through an electrolyte solution to cause a chemical reaction. For hydrogen peroxide production, sulfuric acid ( \( H_2SO_4 \) ) is often used as the electrolyte.
It's essential to ensure the right conditions for the electrolytic process, which includes using a specific concentration of sulfuric acid, such as 50%. This concentration helps improve the conductivity of the solution, allowing efficient electrolysis. It's crucial to choose appropriate materials for electrodes, often selecting inert materials that can withstand the reactions without corroding or adding impurities to the products.
In summary, the electrolytic preparation of hydrogen peroxide is carefully controlled through choice of concentration, electrodes, and supporting equipment.

Hydrogen peroxide

Hydrogen peroxide ( \( H_2O_2 \) ) is a simple and well-known chemical compound with a variety of uses ranging from a disinfectant to a bleaching agent. It is composed of two hydrogen atoms and two oxygen atoms.
Hydrogen peroxide is prized for its strong oxidizing properties. This makes it helpful in various industries, such as textiles and pharmaceuticals, as well as for environmental cleaning and disinfection purposes.
As part of its preparation through electrolysis, observing proper handling procedures is crucial because hydrogen peroxide is a reactive chemical that, in concentrated forms, can be hazardous. Through the electrolysis of sulfuric acid, hydrogen peroxide is formed at the anode and collected for use.
Understanding its powerful role and safe handling requirements ensures its effective and safe application.

Sulfuric acid oxidation

In the context of producing hydrogen peroxide, sulfuric acid acts as the electrolyte and undergoes partial oxidation in the process. During the electrolysis of a sulfuric acid solution, the ions present undergo oxidation and reduction reactions.
Specifically, the bisulfate ions ( \( HSO_4^- \) ) present in the solution can participate in reactions at both the anode and cathode. \[ 2 HSO_4^- ightarrow 2 SO_4^{2-} + H_2O_2 + 2H^+ \] This simplified reaction illustrates how bisulfate transforms, ultimately contributing to the production of hydrogen peroxide. This advanced oxidation process is important, as it helps maintain the efficiency of the H_2O_2 output.
The involvement of sulfuric acid is a classic example of how solutions rich in ions are utilized to drive productive electrolysis.

Cathode and anode reactions

Understanding cathode and anode reactions is fundamental when discussing electrochemistry. In an electrolytic cell, reactions at these electrodes differ from regular cells like batteries.
For the electrolytic production of hydrogen peroxide, sulfuric acid solution, a common setup involves the following reactions:

• **At the cathode**: Hydrogen ions ( \( H^+ \) ) gain electrons to form hydrogen gas ( \( H_2 \) ): \[ 2H^+ + 2e^- ightarrow H_2 \]
• **At the anode**: As a result of the oxidizing conditions, water is oxidized to form oxygen gas and more ions are formed, usually releasing oxygen ( \( O_2 \) ) or, in this specific system, form hydrogen peroxide. \[ 2H_2O ightarrow O_2 + 4H^+ + 4e^- \]

The anode reactions are quite advanced but crucial in understanding why hydrogen is typically released at the cathode and not at the anode.
This clear distinction in electrode reactions helps structure the fundamental working principles of electrolysis while producing various chemical compounds.