30 Questions
What is the main difference between an electrochemical cell and an electrolytic cell?
Electrochemical cell converts chemical energy into electrical energy based on spontaneous redox reactions, while an electrolytic cell converts electrical energy into chemical energy for non-spontaneous reactions.
What is the basis for the functioning of an electrochemical cell?
Electrochemical cells operate based on spontaneous redox reactions, where the Gibbs free energy change (ΔG) is negative.
Describe the setup of electrodes in an electrochemical cell versus an electrolytic cell.
In an electrochemical cell, two electrodes are usually placed in separate beakers, while in an electrolytic cell, both electrodes are suspended in the same electrolyte solution or melt.
What is the primary purpose of a fuel cell?
The main purpose of a fuel cell is to convert chemical energy directly into electrical energy through redox reactions.
Explain the importance of the Nernst Equation in electrochemistry.
The Nernst Equation is crucial for determining the cell potential under non-standard conditions, providing insights into reaction spontaneity.
How do batteries differ from fuel cells in terms of energy conversion?
Batteries store and release electrical energy through chemical reactions, while fuel cells directly convert chemical energy into electrical energy.
Why does the conductivity of an electrolyte decrease on dilution?
The number of ions per unit volume increases on dilution, leading to a decrease in conductivity.
Define limiting molar conductivity.
Limiting molar conductivity is the molar conductivity of an electrolyte solution at infinite dilution.
State Kohlrausch’s law of independent migration of ions and provide one application.
Kohlrausch’s law states that each ion in an electrolyte solution migrates independently. One application is in determining the molar conductivity of strong electrolytes.
Define molar conductivity (Lm).
Molar conductivity (Lm) is the conductivity of a solution containing 1 mole of electrolyte.
Define Kohlrausch’s law of independent migration of ions.
Kohlrausch’s law states that each ion in an electrolyte solution moves independently and contributes to the overall conductivity.
Define limiting molar conductivity.
Limiting molar conductivity is the molar conductivity of an electrolyte solution at infinite dilution.
What is the formula to calculate Ecell for a half cell reaction?
Ecell = E°cell − 0.0591 [Cr3+ ]^2 log n [Cr2O7^2- ][H+ ]^14
What is the standard cell potential (E°cell) for the given reaction?
1.33 V
What is the value of Ecell for the oxidation-reduction reaction involving Zn and Cu ions?
0.782 V
Why does conductivity decrease with a decrease in concentration for both weak and strong electrolytes?
The number of ions per unit volume that carry the current in a solution decreases on dilution.
What is the value of DG° for the given reaction?
-517.24 kJ mol–1
If the external opposing potential is less than 2.71 V, in which direction will the current flow?
From Cu to Mg
What is the overall reaction that takes place in a mercury cell during its operation?
Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(s) + 2H2O(l)
Why is a mercury cell considered a primary battery?
It can only be used once and cannot be recharged.
What is the advantage of a mercury cell in terms of cell potential?
The cell potential remains constant during its lifetime.
What type of cell is the lead storage battery?
It is a secondary cell.
What is the net reaction that occurs during the recharging of a lead storage battery?
2PbSO4(s) + 2H2O(l) → Pb(s) + PbO2(s) + 2H2SO4(aq)
Which cell was used in the Apollo space program?
Hydrogen oxygen fuel cell
Explain how molar conductivity changes with concentration for a weak electrolyte.
Molar conductivity increases with dilution for a weak electrolyte due to increased dissociation of ions.
Describe the relationship between molar conductivity and concentration for a strong electrolyte.
Molar conductivity decreases with dilution for a strong electrolyte due to fewer ions being present in solution.
What is the cell constant if the resistance of a conductivity cell containing 0.001 M KCl solution at 298 K is 1500 Ω and the conductivity of the solution is 0.146 × 10^–3 S cm^–1?
The cell constant is 0.097 cm^–1.
How many coulombs are required for the oxidation of 1 mol of H2O to O2?
4 Faradays.
Explain why Cl2 gas is liberated at the anode instead of O2 gas during the electrolysis of aqueous NaCl despite having higher E° value for O2.
Chlorine gas is liberated at the anode due to kinetic factors, even though O2 has a higher standard reduction potential.
How much charge is required for the reduction of 1 mol of Zn2+ to Zn?
2 Faradays.
Test your knowledge on molar conductivity of solutions, how it changes with concentration for weak and strong electrolytes, and calculating cell constant of a conductivity cell. Also includes a question on the amount of coulombs required for the oxidation of water to oxygen.
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