Problem 165 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following Column-I \(\quad\) Column-II (a) Charge on one mole of (p) 1 Faraday electron. (b) \(108 \mathrm{~g}\) of silver deposited (q) 96500 coulomb at electrode. $$ \begin{array}{ll} \hline \text { Column-I } & \text { Column-II } \\ \hline \text { (c) 22.4 L of hydrogen at } & \text { (r) 2 Faraday } \\ \text { STP collected. } & \\ \text { (d) } 8 \mathrm{~g} \text { of oxygen collected. } & \text { (t) } 5.6 \mathrm{~L} \text { at STP } \\ \hline \end{array} $$

Step-by-Step Solution

Answer

(a-q), (b-p), (c-r), (d-t)

Step 1: Understanding Faraday's Constant

Faraday's constant is the charge of one mole of electrons, which is approximately 96500 coulombs. Therefore, Column-I(a) 'Charge on one mole of electron' matches with Column-II(q) '96500 coulomb'.

Step 2: Calculating Silver Deposition

According to Faraday's laws of electrolysis, the amount of substance deposited is proportional to the charge passed through the system. Silver (Ag) has a molar mass of 108 g/mol and requires one mole of electrons for deposition (equivalent to 1 Faraday). Thus, Column-I(b) '108 g of silver deposited' matches with Column-II(p) '1 Faraday'.

Step 3: Volume of Hydrogen at STP

One mole of any gas occupies 22.4 L at STP. Since hydrogen gas is H2, 1 mole of H2 equals 1 Faraday in electrochemical processes, representing 2 moles of protons. So Column-I(c) '22.4 L of hydrogen at STP' matches with Column-II(r) '2 Faraday'.

Step 4: Understanding Oxygen Collection at STP

Oxygen (O2) has 32 g/mol as its molar mass. Oxygen requires 4 moles of electrons per mole of O2 for electrolytic production. Thus, 8 g of oxygen represents 0.25 moles of O2 (1/4th of 32 g/mol), leading to production of 5.6 L at STP (1/4th of 22.4 L). Therefore, Column-I(d) '8 g of oxygen collected' matches with Column-II(t) '5.6 L at STP'.

Key Concepts

Faraday's Constant

Faraday's constant is a fundamental value essential for understanding electrochemical reactions. It represents the total electric charge carried by one mole of electrons. This constant is crucial in various calculations involving electrolysis and electrochemical cells.

• The approximate value of Faraday's constant is 96500 coulombs per mole of electrons.

This means if you have one mole of electrons, they collectively carry a charge of 96500 coulombs. This value helps us relate the amount of substance transformed during electrolysis to the charge passed through the system.
The concept is named after Michael Faraday, who made significant contributions to the field of electrochemistry. Understanding this constant allows us to calculate how much of a particular substance can be deposited or dissolved when a certain quantity of electricity is used.

Electrolysis

Electrolysis is a chemical process that uses electrical energy to drive a non-spontaneous chemical reaction. It is widely used in various industrial applications, including metal plating, purification, and manufacturing. This process involves passing an electric current through a substance to effect a chemical change.

• During electrolysis, **anions** are drawn to the **anode** (positive electrode), and **cations** to the **cathode** (negative electrode).

Faraday's laws of electrolysis help predict the amount of substance deposited or released during this process, linking the mass of substance altered at an electrode to the quantity of electricity passed through it. These laws are vital to calculating the deposition and oxidation-reduction reactions. Electrolysis allows the extraction and refining of metals, such as copper and aluminum, and the production of gases like hydrogen and oxygen from water.

Molar Volume of Gases at STP

At standard temperature and pressure (STP), which is defined as a temperature of 0°C (273.15 K) and a pressure of 1 atmosphere (atm), all gases occupy a characteristic volume called the molar volume. This value is crucial when dealing with gases in reactions and calculations.

• One mole of an ideal gas occupies a volume of 22.4 liters at STP.

This concept is particularly useful in stoichiometry and gas-related calculations, as it allows for an easy conversion between moles of a gas and its volume. For example, whether you're evaluating hydrogen, oxygen, or nitrogen, you can apply this constant molar volume as a simplistic model to assume ideal behavior of gases under STP conditions. This is particularly significant in electrolysis, where knowing the produced gas quantity by volume can determine process efficiency.