Problem 60 - A Complete Resource Book in Chemistry for JEE Main

Question

The electric charge for electrode deposition of one gram equivalent of a substance is (a) charge on one mole of electrons (b) 96500 couloumbs per second (c) one ampere per second (d) one ampere for one hour

Step-by-Step Solution

Answer

The answer is (a) charge on one mole of electrons.

Step 1: Understanding Faraday's Law of Electrolysis

According to Faraday's laws, the amount of substance deposited at an electrode in electrolysis is directly proportional to the charge passed. One faraday, which is equivalent to 96500 coulombs, corresponds to the charge carried by one mole of electrons.

Step 2: Identifying the Unit for Electric Charge

The unit for electric charge in the context of electrolysis is measured in coulombs. Specifically, one faraday is the charge required to deposit one gram equivalent of a substance, equal to the charge of one mole of electrons.

Step 3: Analyzing the Options

Option (a), 'charge on one mole of electrons', directly corresponds to the definition of one faraday, which is 96500 coulombs. Option (b) is incorrect because it states '96500 coulombs per second' as a charge; this is a power (in watts), not a simple charge. Options (c) and (d) describe current and time, not the electric charge directly.

Step 4: Conclusion

The correct answer is option (a) because it directly relates to the amount of electric charge represented by one faraday, which is used to deposit one gram equivalent of substance on an electrode.

Key Concepts

Electric Charge

Electric charge is a fundamental concept in the study of electrolysis. In this context, it refers to the quantity of electricity required to drive the deposition of substances during an electrochemical reaction. Electric charge is measured in

• coulombs (C),
• ampere-seconds (A·s),
• or even faradays in specific chemical contexts.

Understanding how electric charge works helps clarify the process of electrolysis. The quantity of charge passed during electrolysis determines how much of a substance gets deposited or dissolved at the electrodes. One coulomb is the charge passed if a constant current of one ampere flows for one second. This is a useful unit for quick calculations. However, in electrolysis, we often use faradays. A faraday represents the charge of one mole of electrons, equivalent to 96500 coulombs. This unique measurement simplifies computations involving the electrochemical reactions of substances.

Mole of Electrons

The concept of a mole of electrons is rooted in Avogadro's number, which is about \( 6.022 imes 10^{23} \). This number represents the quantity of particles, such as atoms or electrons, in one mole of a substance. In electrochemistry, the charge carried by one mole of electrons is significant because it facilitates the deposition of substances during electrolysis.Why is it important?

• It provides a basis for understanding the relationship between electric charge and chemical quantities.
• It helps in determining the charge needed for electrochemical reactions.
• Recognizing the charge on a mole of electrons aids in the calculation of electrochemical equivalents.

Relating this to Faraday's law, it's crucial to note that one mole of electrons corresponds to a faraday of charge, equal to 96500 coulombs. This relationship forms the backbone of understanding how electric charge interacts with matter in electrochemical cells.

Gram Equivalent

In chemistry, the term gram equivalent refers to the quantity of a substance, measured in grams, that reacts with or is equivalent to one mole of hydrogen ions (\( H^+ \)) in an acid-base reaction, or one mole of electrons in a redox reaction. This concept is essential in stoichiometry and electrochemistry. Key Points:

• Gram equivalent helps in understanding the proportion of substances involved in chemical reactions.
• It relates to the quantity of electricity needed for reactions in electrolysis.
• It provides a bridge to calculate how much of a substance is deposited or dissolved in electrochemical cells.

When relating gram equivalent to electrolysis, one faraday, or 96500 coulombs of charge, is required to deposit or dissolve one gram equivalent of a chemical substance at an electrode. This connection is vital for understanding and performing electrochemical processes efficiently.