For hydrogen - oxygen fuel cell at one $atm$ and $298\, K$
$H_2(g)+\frac {1}{2} O_2(g) \to H_2O_{(l)} ; \Delta G^\circ=-240\, kJ$
$E^\circ$ for the cell is approximately, (Given $F \,= \,96,500 \,C$)
- $1.25 \,V$
- $1.26 \,V$
- $2.48\, V$
- $2.5\, V$
The Correct Option is A
Solution and Explanation
where, $n=$ number of moles of electrons
transferred $=2$
$\Rightarrow F=96500\, C$
$\Delta G^{\circ}=-240\, kJ =-240 \times 1000\, J$
$\therefore E^{\circ}=\frac{-240000}{-2 \times 96500}=1.24\, V$
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Statement (I) : With increasing voltage, the sequence of deposition of metals on the cathode will be Ag, Hg and Cu
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Concepts Used:
Electrochemical Cells
An electrochemical cell is a device that is used to create electrical energy through the chemical reactions which are involved in it. The electrical energy supplied to electrochemical cells is used to smooth the chemical reactions. In the electrochemical cell, the involved devices have the ability to convert the chemical energy to electrical energy or vice-versa.
Classification of Electrochemical Cell:
Cathode
- Denoted by a positive sign since electrons are consumed here
- A reduction reaction occurs in the cathode of an electrochemical cell
- Electrons move into the cathode
Anode
- Denoted by a negative sign since electrons are liberated here
- An oxidation reaction occurs here
- Electrons move out of the anode
Types of Electrochemical Cells:
Galvanic cells (also known as Voltaic cells)
- Chemical energy is transformed into electrical energy.
- The redox reactions are spontaneous in nature.
- The anode is negatively charged and the cathode is positively charged.
- The electrons originate from the species that undergo oxidation.
Electrolytic cells
- Electrical energy is transformed into chemical energy.
- The redox reactions are non-spontaneous.
- These cells are positively charged anode and negatively charged cathode.
- Electrons originate from an external source.