Electrochemistry
Q. If the concentration of Cu²⁺ in a cell is increased, what happens to the cell potential?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
Increasing the concentration of Cu²⁺ increases the cell potential according to the Nernst equation.
Correct Answer: A — Increases
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Q. In a concentration cell, if the concentration of one half-cell is 0.1 M and the other is 1 M, what is the cell potential?
A.
0.059 V
B.
0.118 V
C.
0.0591 V
D.
0.1181 V
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Solution
Using the Nernst equation, E = (0.0591/n) log([C1/C2]), where n=1.
Correct Answer: B — 0.118 V
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Q. In a Daniell cell, which metal acts as the anode?
A.
Copper
B.
Zinc
C.
Silver
D.
Lead
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Solution
In a Daniell cell, Zinc acts as the anode.
Correct Answer: B — Zinc
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Q. In a galvanic cell, if the anode reaction is 2Ag⁺ + 2e⁻ → 2Ag, what is the cathode reaction? (2022)
A.
Cu²⁺ + 2e⁻ → Cu
B.
Zn²⁺ + 2e⁻ → Zn
C.
Fe²⁺ + 2e⁻ → Fe
D.
Pb²⁺ + 2e⁻ → Pb
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Solution
The cathode reaction must be a reduction reaction, and Cu²⁺ + 2e⁻ → Cu is a common cathode reaction.
Correct Answer: A — Cu²⁺ + 2e⁻ → Cu
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Q. In a galvanic cell, if the anode reaction is 2H₂ → 4H⁺ + 4e⁻, what is the cathode reaction?
A.
O₂ + 4e⁻ + 4H⁺ → 2H₂O
B.
2H₂O + 4e⁻ → 2H₂ + O₂
C.
4H⁺ + 4e⁻ → 2H₂
D.
2H₂ + O₂ → 2H₂O
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Solution
The cathode reaction is O₂ + 4e⁻ + 4H⁺ → 2H₂O.
Correct Answer: A — O₂ + 4e⁻ + 4H⁺ → 2H₂O
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Q. In a galvanic cell, if the anode reaction is Ag⁺ + e⁻ → Ag, what is the cathode reaction?
A.
Cu²⁺ + 2e⁻ → Cu
B.
Zn²⁺ + 2e⁻ → Zn
C.
Fe²⁺ + 2e⁻ → Fe
D.
Pb²⁺ + 2e⁻ → Pb
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Solution
The cathode reaction must be a reduction; Ag⁺ + e⁻ → Ag is the anode reaction.
Correct Answer: A — Cu²⁺ + 2e⁻ → Cu
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Q. In a galvanic cell, if the anode reaction is Zn → Zn²⁺ + 2e⁻, what is the cathode reaction if the cathode is Cu²⁺ + 2e⁻ → Cu?
A.
Cu → Cu²⁺ + 2e⁻
B.
Zn²⁺ + 2e⁻ → Zn
C.
Zn + Cu²⁺ → Zn²⁺ + Cu
D.
Cu²⁺ + 2e⁻ → Cu
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Solution
The cathode reaction is Cu²⁺ + 2e⁻ → Cu.
Correct Answer: D — Cu²⁺ + 2e⁻ → Cu
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Q. In electrolysis, if 1 mole of electrons is transferred, how many grams of copper can be deposited from Cu²⁺?
A.
63.5 g
B.
31.75 g
C.
127 g
D.
159 g
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Solution
1 mole of Cu²⁺ deposits 63.5 g of copper.
Correct Answer: A — 63.5 g
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Q. In electrolysis, if the current is 2 A and the time is 30 minutes, how many moles of electrons are transferred?
A.
0.1 mol
B.
0.2 mol
C.
0.3 mol
D.
0.4 mol
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Solution
Using the formula: moles = (current × time) / (n × F), where n=1 for electrons and F=96500 C/mol.
Correct Answer: B — 0.2 mol
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Q. In electrolysis, the process of oxidation occurs at the: (2023)
A.
Anode
B.
Cathode
C.
Electrolyte
D.
None of the above
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Solution
In electrolysis, oxidation occurs at the anode.
Correct Answer: A — Anode
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Q. In electrolysis, the process of oxidation occurs at the: (2023) 2023
A.
Anode
B.
Cathode
C.
Electrolyte
D.
None of the above
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Solution
In electrolysis, oxidation occurs at the anode.
Correct Answer: A — Anode
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Q. In electrolysis, what is produced at the anode when NaCl solution is electrolyzed? (2022)
A.
Hydrogen gas
B.
Chlorine gas
C.
Sodium metal
D.
Oxygen gas
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Solution
Chlorine gas is produced at the anode during the electrolysis of NaCl solution.
Correct Answer: B — Chlorine gas
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Q. What is the cell potential of a Daniell cell at standard conditions?
A.
1.10 V
B.
1.96 V
C.
0.76 V
D.
0.34 V
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Solution
The standard cell potential of a Daniell cell is 1.10 V.
Correct Answer: A — 1.10 V
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Q. What is the cell potential of a galvanic cell with E° = 1.5 V and Q = 10?
A.
1.2 V
B.
1.0 V
C.
1.3 V
D.
1.4 V
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Solution
Using the Nernst equation, E = E° - (RT/nF)lnQ, we find E ≈ 1.0 V.
Correct Answer: B — 1.0 V
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Q. What is the effect of temperature on the cell potential according to the Nernst equation?
A.
Increases with temperature
B.
Decreases with temperature
C.
No effect
D.
Depends on the reaction
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Solution
According to the Nernst equation, the cell potential generally increases with temperature.
Correct Answer: A — Increases with temperature
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Q. What is the Faraday's constant value?
A.
96485 C/mol
B.
96500 C/mol
C.
96500 A·s/mol
D.
96480 C/mol
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Solution
Faraday's constant is approximately 96485 C/mol.
Correct Answer: A — 96485 C/mol
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Q. What is the Faraday's constant?
A.
96485 C/mol
B.
96500 C/mol
C.
96500 J/mol
D.
96485 J/mol
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Solution
Faraday's constant is approximately 96485 C/mol.
Correct Answer: A — 96485 C/mol
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Q. What is the Nernst equation for a cell at 298 K with E° = 0.77 V and [Zn²⁺] = 0.01 M?
A.
E = 0.77 - 0.0591 log(0.01)
B.
E = 0.77 + 0.0591 log(0.01)
C.
E = 0.77 - 0.0591 log(100)
D.
E = 0.77 + 0.0591 log(100)
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Solution
Using the Nernst equation: E = E° - (0.0591/n) log([Zn²⁺]), where n=2.
Correct Answer: A — E = 0.77 - 0.0591 log(0.01)
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Q. What is the Nernst equation used for calculating the cell potential at non-standard conditions? (2023)
A.
E = E° - (RT/nF)lnQ
B.
E = E° + (RT/nF)lnQ
C.
E = E° - (nF/RT)lnQ
D.
E = E° + (nF/RT)lnQ
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Solution
The Nernst equation is E = E° - (RT/nF)lnQ, where E is the cell potential, E° is the standard potential, R is the gas constant, T is the temperature, n is the number of moles of electrons, and F is Faraday's constant.
Correct Answer: A — E = E° - (RT/nF)lnQ
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Q. What is the Nernst equation used for? (2023) 2023
A.
Calculating pH
B.
Determining cell potential
C.
Measuring current
D.
Finding resistance
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Solution
The Nernst equation is used to determine the cell potential under non-standard conditions.
Correct Answer: B — Determining cell potential
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Q. What is the product of electrolysis of water?
A.
Hydrogen and Oxygen
B.
Hydrogen and Carbon
C.
Oxygen and Nitrogen
D.
Hydrogen and Chlorine
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Solution
The products of electrolysis of water are hydrogen and oxygen.
Correct Answer: A — Hydrogen and Oxygen
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Q. What is the reduction potential of the half-reaction 2H⁺ + 2e⁻ → H₂?
A.
0.00 V
B.
0.34 V
C.
0.76 V
D.
1.23 V
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Solution
The standard reduction potential for 2H⁺ + 2e⁻ → H₂ is 0.00 V.
Correct Answer: D — 1.23 V
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Q. What is the relationship between Gibbs free energy (ΔG) and cell potential (E) in electrochemistry?
A.
ΔG = -nFE
B.
ΔG = nFE
C.
ΔG = -E/nF
D.
ΔG = E/nF
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Solution
The relationship is ΔG = -nFE, where n is the number of moles of electrons transferred.
Correct Answer: A — ΔG = -nFE
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Q. What is the standard electrode potential of the half-reaction Zn²⁺ + 2e⁻ → Zn?
A.
0.76 V
B.
0.34 V
C.
-0.76 V
D.
-0.34 V
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Solution
The standard electrode potential for Zn²⁺/Zn is -0.76 V.
Correct Answer: C — -0.76 V
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Q. What is the standard electrode potential of the hydrogen electrode? (2023) 2023
A.
0 V
B.
1 V
C.
2 V
D.
0.5 V
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Solution
The standard electrode potential of the hydrogen electrode is defined as 0 V.
Correct Answer: A — 0 V
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Q. What is the unit of electrical conductivity? (2023)
A.
Ohm
B.
Siemens
C.
Volt
D.
Ampere
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Solution
The unit of electrical conductivity is Siemens (S).
Correct Answer: B — Siemens
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Q. Which of the following is a primary cell? (2023) 2023
A.
Lead-acid battery
B.
Nickel-cadmium battery
C.
Zinc-carbon battery
D.
Lithium-ion battery
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Solution
The zinc-carbon battery is a type of primary cell, which cannot be recharged.
Correct Answer: C — Zinc-carbon battery
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Q. Which of the following statements is true about galvanic cells? (2020)
A.
They convert chemical energy to electrical energy
B.
They require an external power source
C.
They operate only in acidic solutions
D.
They are always non-spontaneous
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Solution
Galvanic cells convert chemical energy into electrical energy spontaneously.
Correct Answer: A — They convert chemical energy to electrical energy
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