Problem 25 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Faraday's laws of electrolysis are related to the (a) atomic number of the reactants. (b) atomic number of the anion. (c) equivalent weight of the electrolyte. (d) speed of the cation.

Step-by-Step Solution

Answer

(c) equivalent weight of the electrolyte.

Step 1: Understand the Concept

Faraday's laws of electrolysis state that the amount of substance produced at each electrode during electrolysis is proportional to the quantity of electricity passed through the electrolyte. These laws focus on the relationship between the mass of the substance separated and the electric charge.

Step 2: Identify the Key Factor

Faraday's laws are majorly concerned with quantities that influence the mass of substances deposited or dissolved at electrodes rather than atomic properties like atomic numbers or speed of ions.

Step 3: Apply the Laws

According to Faraday's first law, the mass of a substance (m) altered at an electrode is directly proportional to the total electric charge (Q) passed through the circuit. The equation is:\[ m = \frac{Q}{F} \cdot \text{Equivalent weight} \]Here, F is Faraday's constant. This equation highlights the role of equivalent weight in determining the mass of the product.

Step 4: Choose the Correct Option

Since the equivalent weight affects how much substance is deposited during electrolysis, the correct answer involves the equivalent weight of the electrolyte.

Key Concepts

Equivalent Weight

The equivalent weight of a substance is a crucial concept in the context of electrolysis because it helps us understand how different substances interact with electric charges. In simple terms, equivalent weight refers to the amount of a substance that will react with or displace a fixed amount of another substance. Often, this is based on hydrogen's standard equivalent, where one equivalent of hydrogen weighs 1 gram. For acids and bases, equivalent weight can refer to how much acid is needed to neutralize a base or vice versa.

• It is determined from the molar mass divided by the valency (or number of electrons exchanged per molecule). In a reaction where sodium, with a valency of 1, participates, the whole molar mass counts as the equivalent weight.
• This concept allows chemists to predict the quantity of a product that will form during chemical reactions, including those occurring in electrolysis.
• Understanding equivalent weight becomes particularly useful when applying Faraday's laws, as it allows us to connect electric charge with chemical transformation.

In essence, by linking equivalent weight with Faraday’s first law, one can determine the mass of substance deposited at an electrode during electrolysis.

Electrolysis

Electrolysis is an electrochemical process that uses direct current (DC) voltage to drive a non-spontaneous chemical reaction. This process plays a significant role in different industries, including metal plating, electrorefining, and the production of chemicals like chlorine and hydrogen gas. During electrolysis, electrical energy is transformed into chemical energy, causing substances to be decomposed or transformed at the electrodes.

• This occurs in a medium known as an electrolyte, which allows ions to move freely and enable the flow of electric charge.
• Two main changes occur during electrolysis: oxidation, which occurs at the anode (positive electrode), and reduction, which occurs at the cathode (negative electrode).
• To grasp the complete electrolysis process, understanding the movement of ions and the role that electricity plays in these reactions is fundamental.

Faraday’s laws revolve around this electrochemical process, providing the guidelines to calculate the effectiveness and efficiency of the reactions occurring.

Electric Charge

An electric charge is a fundamental property of matter that causes it to experience a force in an electromagnetic field. It plays a crucial role in electrolysis, as it is the movement of electric charges that results in chemical changes at the electrodes. There are two types of electric charges: positive and negative, and like charges repel each other, while opposite charges attract.

• In the context of electrolysis, electric charges are transferred through the electrodes: electrons enter through the cathode where reduction happens, and exit through the anode, where oxidation occurs.
• Faraday's laws highlight the direct proportional relationship between these electric charges and the mass of substance deposited or released in an electrochemical reaction.
• Understanding electric charge is essential not just for electrolysis but also for grasping broader concepts in electricity and magnetism.

Hence, electric charge facilitates the linkage between physical electric phenomena and chemical changes that are central to electrochemical processes.