Define fuel cell and write its two advantages.

A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Advantages of Fuel cell: (1) Unlike conventional cells, the fuel cells do not have to be discharged when the chemicals are consumed. (2) They are non polluting because the only reaction product is water (for hydrogen–oxygen fuel cell).

Give reason: On the basis of E ∘ values, O 2 gas should be liberated at anode but it is Cl 2 gas which is liberated during electrolysis of aqueous NaCl .

It is due to the phenomenon of over–voltage. Experimentally, it is observed that the actual voltage required for electrolysis is greater than that calculated from standard potentials. This addition voltage required is called over–voltage. The concept of requirement of higher voltage is because of the presence of hydrogen bonds between the water molecules. Thus, for oxygen to be liberated after the removal of the bonds, a very high voltage is very important. The over–voltage required for formation of oxygen is much larger than that required for the formation of chlorine. Hence, chlorine gas which is liberated in the electrolysis of aqueous NaCl .

The cell in which the following reaction occurs: 2 F e 3 + a q + 2 I - a q → 2 F e 2 + a q + I 2 ( s ) has E c e l l 0 = 0.236 V at 298 K . Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.

Given E c e l l 0 = 0.236 V T = 298 K 2 Fe 3 + aq + 2 I - aq → 2 Fe 2 + aq + I 2 ( s ) Here, n = 2 and F = 96500 We know that: ∆ r G 0 = - n F E c e l l 0 = - 2 × 96500 × 0.236 = - 45 , 548 J m o l - 1 = - 45.54 k J m o l - 1 = - 45.54 × 10 3 J m o l - 1 Again, ∆ r G = ∆ r G 0 + 2.303 R T log ⁡ Q At equilibrium ∴ ∆ r G = 0 and Q = K c ∆ r G 0 = - 2.303 R T log ⁡ K c ⇒ log ⁡ K c = - ∆ r G 0 2.303 R T = - ( - 45.54 × 10 3 ) 2.303 × 8.314 × 298 = 7.981 ∴ K c = A n t i l o g 7.981 = 9.57 × 10 7

E M B I B E

Chemistry Crash Course (Based on Revised Syllabus-2023)>Chapter -1 - Electrochemistry>Exercise>Q 43

HARD

12th Meghalaya Board

IMPORTANT

Earn 100

The unit of conductivity (specific conductance) is -

70.63% studentsanswered this correctly

Chapter-Wise 3D Chemistry Videos from Embibe Experts Chemistry Crash Course (Based on Revised Syllabus-2023)

05 min 07 sec

Fuel Cell

Galvanic cells that are designed to convert the energy of combustion of fuels like hydrogen and methane directly into electrical energy are called fuel cells...

05 min 28 sec

Lead Storage Battery

The lead storage battery is commonly used in automobiles and inverters. Let’s understand how these batteries provide electrical energy! Watch this video and...