Question on Electrochemistry
The standard reduction potential for Cu2+/Cu is +0.34 V.
What will the reduction potential for the above couple be at pH = 14?
Ksp [Cu(OH)2] = 1.0 * 10–19
Question on Electrochemistry
By how many volts will the reduction potential of a hydrogen electrode change when its solution initially at pH = 0 is neutralized to pH = 7?
Answer:
When the pH = 0, the reduction potential will be 0.0 V. The reduction potential will decrease 0.4137 V when the pH is changed from 0 to 7.
Question on Electrochemistry
3 Faraday of electricity are passed through molten Al2O3 aqueous solution of CuSO4 and molten NaCl in three different electrolytic cells. What will be the molar ratio of Al, Cu, Na deposited at the respective cathodes?
Answer:
1 Faraday of electricity will deposit 1 equivalent of a metal. So 3 equivalents of Al, Cu & Na will be deposited which is same as 1 mole of Al, 1.5 mole of Cu and 3 mole of Na.
Question on Electrochemistry
What is the number of electrons lost during electrolysis of 0.355g of chloride ions?
Question on Electrochemistry
A 7.0V battery produces a constant current of 1.5A for 3 hours. How many Faraday of charge does the battery produce?
Answer:
1 Faraday is 96500 coulomb of charge.
Total charge passed (in Coulomb) = i (in ampere) * t (in seconds) = 1.5 * 3 * 60 * 60 = 16200C = 0.168F
Question on Electrolysis
A certain amount to alkaline water was subject to electrolysis. If, a total of 1 mole of gases is evolved, what is the amount of water that got electrolysed?
Answer:
The reaction for electrolysis of water is as follows;
2H2O = 2H2 + O2
As 3 moles of gases are produced from 2 moles of water, 1 mole of gases will be produced from (2/3) moles of water.
Question on Electrochemistry
The values of Standard Reduction Potential for three metal ions A, B and C are 0.5, -3.0 and -1.2 respectively. Which corresponding metal among the three is the best reducing agent?
Answer:
Standard Reduction Potentials (SRPs) tell us about the potential that a metal ion has to get reduced while Standard Oxidation Potentials (SOPs) tell us about the potential that a metal has to get oxidised. SOP is same in magnitude but opposite in direction compared to SRP. From the given SRP values it is evident that metal ion B has the least SRP value. So, the metal B will be the one which will have the highest standard oxidation potential and hence act as the best reducing agent among the three metal ions.
Question on Cell emf
The Standard Reduction Potentials of Pb2+/Pb and Cu2+/Cu couples are -0.76V and +0.34V respectively. What will be the standard emf of the cell constructed with the two couples mentioned above?
Answer:
From the SRPs given in the question it could be found that, for the cell to be spontaneous Pb2+/Pb should act as the anode and Cu2+/Cu should act as the cathode. Also,
EoCell = EoCathode - EoAnode = 0.34 - (-0.76) = 0.34 + 0.76 = 1.1V
