chemistry : class12 Limiting Molar Conductivity : Conductance in electrolytic solutions : Electrochemistry MCQ Questions and Answers
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Limiting Molar Conductivity
MCQ questions and answers.
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MCQ Questions
1. What is meant by limiting molar conductivity of an electrolyte?
A.
Molar conductivity at infinite dilution
B.
Conductivity at zero temperature
C.
Resistance at infinite concentration
D.
Molar conductivity at maximum concentration
Correct Answer:
Molar conductivity at infinite dilution
Explanation:
Limiting molar conductivity is the molar conductivity of an electrolyte when its concentration approaches zero, or dilution becomes infinite.
2. The symbol commonly used for limiting molar conductivity is:
A.
κ
B.
Λ°m
C.
R
D.
G
Correct Answer:
Λ°m
Explanation:
Limiting molar conductivity is represented by Λ°m, where the superscript degree indicates infinite dilution.
3. The SI unit commonly used for limiting molar conductivity is:
A.
S m⁻¹
B.
S m² mol⁻¹
C.
Ω m
D.
Ω⁻¹ m⁻¹
Correct Answer:
S m² mol⁻¹
Explanation:
Molar conductivity, including limiting molar conductivity, has the unit siemens metre squared per mole, S m² mol⁻¹.
4. According to Kohlrausch's law, the limiting molar conductivity of an electrolyte is equal to:
A.
The product of ionic conductivities
B.
The sum of the individual ionic contributions
C.
The difference between ionic concentrations
D.
The average of the electrode potentials
Correct Answer:
The sum of the individual ionic contributions
Explanation:
Kohlrausch's law states that at infinite dilution, each ion contributes independently to the total limiting molar conductivity.
5. Which expression represents Kohlrausch's law for sodium chloride?
A.
Λ°m(NaCl) = λ°(Na⁺) + λ°(Cl⁻)
B.
Λ°m(NaCl) = λ°(Na⁺) − λ°(Cl⁻)
C.
Λ°m(NaCl) = λ°(Na⁺) × λ°(Cl⁻)
D.
Λ°m(NaCl) = λ°(Na⁺) ÷ λ°(Cl⁻)
Correct Answer:
Λ°m(NaCl) = λ°(Na⁺) + λ°(Cl⁻)
Explanation:
For sodium chloride, the limiting molar conductivity is the sum of the limiting ionic conductivities of Na⁺ and Cl⁻.
6. At infinite dilution, the ions of a strong electrolyte are considered to migrate:
A.
Independently of one another
B.
Only toward the anode
C.
Only toward the cathode
D.
Without responding to an electric field
Correct Answer:
Independently of one another
Explanation:
At infinite dilution, interionic interactions become negligible, so each ion makes an independent contribution to limiting molar conductivity.
7. The limiting molar conductivity of a weak electrolyte is commonly determined using:
A.
Kohlrausch's law
B.
Boyle's law
C.
Faraday's first law only
D.
Henry's law
Correct Answer:
Kohlrausch's law
Explanation:
The limiting molar conductivity of a weak electrolyte can be calculated from the limiting ionic conductivities of its ions using Kohlrausch's law.
8. For calcium chloride, the Kohlrausch expression for limiting molar conductivity is:
A.
Λ°m(CaCl₂) = λ°(Ca²⁺) + 2λ°(Cl⁻)
B.
Λ°m(CaCl₂) = 2λ°(Ca²⁺) + λ°(Cl⁻)
C.
Λ°m(CaCl₂) = λ°(Ca²⁺) − 2λ°(Cl⁻)
D.
Λ°m(CaCl₂) = λ°(Ca²⁺) × 2λ°(Cl⁻)
Correct Answer:
Λ°m(CaCl₂) = λ°(Ca²⁺) + 2λ°(Cl⁻)
Explanation:
One calcium ion and two chloride ions are produced by calcium chloride, so their ionic contributions are added with the corresponding stoichiometric coefficients.
9. As a solution is diluted toward infinite dilution, the molar conductivity of an electrolyte approaches its:
A.
Limiting molar conductivity
B.
Minimum conductivity
C.
Zero molar mass
D.
Electrode potential
Correct Answer:
Limiting molar conductivity
Explanation:
When concentration approaches zero, the molar conductivity approaches a maximum limiting value called limiting molar conductivity.
10. Which factor becomes negligible at infinite dilution, allowing limiting molar conductivity to be calculated from independent ionic contributions?
A.
Interionic attraction
B.
Molar mass of the solvent
C.
Color of the solution
D.
Volume of the electrodes
Correct Answer:
Interionic attraction
Explanation:
At infinite dilution, ions are far apart and interionic attractions become negligible, so each ion contributes independently to limiting molar conductivity.
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