
In a fuel cell, methanol is used as fuel and oxygen gas is used as an oxidizer.
The reaction is:
At 298 K, standard Gibbs energy of formation for are -166.2, -237.2 and 394.4 kJ / mol respectively.
If the standard enthalpy of combustion of methanol is -726 kJ / mol, the efficiency of the fuel cell will be:
(a)- 80%
(b)- 87%
(c)- 90%
(d)- 97%
Answer
512.4k+ views
Hint: The efficiency of the fuel cell is calculated by dividing the standard free energy with the standard enthalpy of combustion. The standard free energy of a reaction is calculated by taking the difference of the sum of standard free energy of the product and the sum of standard free energy of the reactant.
Complete answer:
Standard free energy change of a reaction is defined as the change in free energy which takes place when the reactants in the standard state are converted into the products in their standard state.
It is calculated by the formula:
Standard free energy of formation of a compound is defined as the free energy change which takes place when 1 mole of the compound is formed from its elements taken in their standard states.
So, according to the reaction:
The reaction’s standard free energy change will be:
The standard free energy of carbon dioxide, water, methanol, and oxygen are -394.4, -237.2, 166.2, and 0 respectively. So,
It is found that in a fuel cell the heat evolved during the process is not completely converted into energy, i.e., useful work. The ratio of is called the efficiency of the fuel cell.
The free energy is -702.3kJ / mol and standard enthalpy are -726kJ / mol.
For percentage, 0.97 x 100 = 97%
The efficiency of the fuel cell is 97%
So, the correct answer is “Option D”.
Note: While calculating the standard free energy change of the reaction the number of atoms must be multiplied before each compound according to the reaction. The reaction must be balanced.
Complete answer:
Standard free energy change of a reaction is defined as the change in free energy which takes place when the reactants in the standard state are converted into the products in their standard state.
It is calculated by the formula:
Standard free energy of formation of a compound is defined as the free energy change which takes place when 1 mole of the compound is formed from its elements taken in their standard states.
So, according to the reaction:
The reaction’s standard free energy change will be:
The standard free energy of carbon dioxide, water, methanol, and oxygen are -394.4, -237.2, 166.2, and 0 respectively. So,
It is found that in a fuel cell the heat evolved during the process is not completely converted into energy, i.e., useful work. The ratio of
The free energy is -702.3kJ / mol and standard enthalpy are -726kJ / mol.
For percentage, 0.97 x 100 = 97%
The efficiency of the fuel cell is 97%
So, the correct answer is “Option D”.
Note: While calculating the standard free energy change of the reaction the number of atoms must be multiplied before each compound according to the reaction. The reaction must be balanced.
Recently Updated Pages
Master Class 11 Physics: Engaging Questions & Answers for Success

Master Class 11 Chemistry: Engaging Questions & Answers for Success

Master Class 11 Biology: Engaging Questions & Answers for Success

Class 11 Question and Answer - Your Ultimate Solutions Guide

Master Class 11 Business Studies: Engaging Questions & Answers for Success

Master Class 11 Computer Science: Engaging Questions & Answers for Success

Trending doubts
Explain why it is said like that Mock drill is use class 11 social science CBSE

The non protein part of an enzyme is a A Prosthetic class 11 biology CBSE

Which of the following blood vessels in the circulatory class 11 biology CBSE

What is a zygomorphic flower Give example class 11 biology CBSE

1 ton equals to A 100 kg B 1000 kg C 10 kg D 10000 class 11 physics CBSE

The deoxygenated blood from the hind limbs of the frog class 11 biology CBSE
