Write cell reaction of the following electrochemical
cell and calculate e.m.f. and G° of the cell :
2 Cd Cd KCl (1M) Hg Cl , Hg 2 2(s)
[Given : 2+ Cd /Cd E 0.40 V and E 0.28 V]
Answers
Answer:
Galvanic cells
Nernst equation
Batteries; electrolysis
Balancing Redox Reactions
A redox reaction involves a transfer of electrons from one species
to another. This results in a change in oxidation number.
Oxidation (reducing agent): loss of electrons
Reduction (oxidizing agent): gain of electrons
these reactions must occur together
example: thermal decomposition of potassium chlorate
2 K
|{z}
+1
Cl
|{z}
+5
O3
|{z}
2⇥3
(s) ⌦ 2 K
|{z}
+1
Cl
|{z}
1
(s)+3 O2
|{z}
0⇥2
(g)
example: combustion of methane
C
|{z}
Fuel cells
o direct production of electricity (electrochemical process)
o requires a continuous supply of reactants
o very efficient
o the only waste product is water !
Cathode (r
Electrolysis of molten NaCl
o molten state ⇒ ions can move freely
o inert electrodes
o E°
cell = -4 V: must supply at least 4 V from a battery
o anions move towards the anode (oxidation site)
o cations move towards the cathode (reduction site)
o extract electron from Cl–
, force electron onto Na+
→ Na(s) E° = -2.71 V
Explanation: