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Practice each question, then open the answer or worked solution.
Can absolute electrode potential of an electrode be measured?
No. It cannot be measured. We can only measure the difference in electrode potential between the two half-cells. We can also measure electrode potential difference concerning a standard electrode.
Can E°cell or ΔrG° for cell reaction ever be equal to zero?
E° Cell or ∆r G° can never be equal to zero. The only standard electrode potential which is arbitrarily assigned the value zero is the standard hydrogen electrode (SHE). Since everything else is measured concerning SHE; the E° cell can never be zero.
Under what condition is ECell = 0 or ΔrG = 0?
Electrolysis happens when a redox reaction occurs. Like all reactions, redox reaction to moves towards equilibrium. At equilibrium condition, the cell has discharged completely, and cell potential drops to zero.
∆rG= -nF E cell =0
What does the negative sign in the expression E°Zn2+/Zn = -0.76V mean?
A negative value is that hydrogen gas is more stable than the reduced form of species. Here, the reduced form (Zn) is not stable. It is difficult to reduce Zn2+ to Zn. So, the reverse is more likely to happen. Zn would rather get oxidized to Zn2+ and H+ will get reduced
Aqueous copper sulphate solution and aqueous silver nitrate solution are electrolysed by 1 ampere current for 10 minutes in separate electrolytic cells. Will, the mass of copper and silver, deposited on the cathode be the same or different? Explain your answer.
W= itE/96500
= 1×10×60×31.75/96500
Equivalent mass of Cu2+ is different from the equivalent mass of Ag+ so obviously the mass of copper deposited will not be the same as the mass of silver deposited.
Depict the galvanic cell in which the cell reaction is Cu + 2Ag+→ 2Ag + Cu2+
Anode- Oxidation half-cell: Cu → Cu2+ + 2e-
Cathode- Reduction half-cell: 2Ag+ + 2e- →2Ag
Overall reaction : Cu + 2Ag+→ Cu2+ + 2Ag
Cu|Cu2+(aq,1M) || Ag+(aq, 1M)| Ag
Value of standard electrode potential for the oxidation of Cl– ions is more positive than that of water, even then in the electrolysis of aqueous sodium chloride, why is Cl–oxidised at anode instead of water?
The oxidation of water to oxygen is kinetically unfavourable and requires excess potential called over-potential. Over-potential is the excess potential required to drive a reaction at a particular rate.
What is electrode potential?
The potential difference developed between an electrode and electrolyte is called the electrode potential.
Standard electrode potential will be always reduction potential.
Consider the following diagram in which an electrochemical cell is coupled to an electrolytic cell. What will be the polarity of electrodes ‘A’ and ‘B’ in the electrolytic cell?
Zinc goes into solution as Zn2+ and leaves behind the electrons on Electrode A making it negatively charged. Cu2+ from the solution deposits on Electrode B making it positively charged.
Electrode A polarity- negative
Electrode B polarity- positive.
Why is alternating current used for measuring the resistance of an electrolytic solution?
The alternating current keeps the concentration of ions constant whereas direct current changes the concentration of ions. That is why alternating current used for measuring the resistance of an electrolytic solution.