JEE Main - Conductance in electrolytic solutions molar conductivities and Kohlrausch's law Question Bank with Options

1. The molar conductivity of CaSO₄ at infinite dilution is approximately 130 S cm² mol⁻¹. If Λm°(Ca²⁺) = 59.5 S cm² mol⁻¹ and Λm°(SO₄²⁻) = 160 S cm² mol⁻¹, what would be the expected molar conductivity of CaSO₄ at infinite dilution based on Kohlrausch's law?

A) 100.5 S cm² mol⁻¹

B) 219.5 S cm² mol⁻¹

C) 130 S cm² mol⁻¹

D) 260 S cm² mol⁻¹

2. What is the main reason for the decrease in molar conductivity of strong electrolytes with increasing concentration?

A) Decreased number of ions

B) Reduced ionic mobility due to inter-ionic attraction and increased viscosity

C) Increased degree of dissociation

D) Change in the nature of the solvent

3. For a strong electrolyte, the plot of Λm versus √C is a:

A) Straight line with positive slope

B) Straight line with negative slope

C) Parabola

D) Hyperbola

4. The molar conductivity of a solution of concentration C can be expressed as Λm = Λm° - A√C for dilute solutions, where A is a constant. This equation is known as:

A) Kohlrausch's equation

B) Debye-Hückel-Onsager equation

C) Arrhenius equation

D) Henderson-Hasselbalch equation

5. The limiting molar conductivity of an electrolyte is the molar conductivity at:

A) Unit concentration

B) Zero concentration

C) Saturation concentration

D) Room temperature

6. Which ion exhibits the lowest molar conductivity at infinite dilution in aqueous solution among alkali metals?

A) Li⁺

B) Na⁺

C) K⁺

D) Rb⁺

7. The molar conductivity of a 0.01 M solution of a weak acid HA is 150 S cm² mol⁻¹, and its limiting molar conductivity is 300 S cm² mol⁻¹. What is the degree of dissociation of HA?

A) 0.5

B) 0.25

C) 0.75

D) 0.15

8. Kohlrausch's law states that at infinite dilution, the molar conductivity of an electrolyte is the sum of the contributions of the individual ions. This law is a consequence of:

A) Ohm's Law

B) Faraday's Laws

C) The independence of ionic migration

D) The law of mass action

9. Conductivity (κ) is related to conductance (G) and cell constant (G*) by:

A) κ = G * G*

B) κ = G / G*

C) κ = G* / G

D) κ = 1 / (G * G*)

10. The cell constant (G*) of a conductivity cell is given by:

A) Length / Area

B) Area / Length

C) Resistivity * Conductance

D) Resistance * Conductivity

11. The phenomenon that explains the increase in molar conductivity of weak electrolytes with dilution is:

A) Increased inter-ionic attraction

B) Increased dissociation

C) Decreased ionic mobility

D) Increased solvent viscosity

12. The molar conductivity of AgCl at infinite dilution is 138.3 S cm² mol⁻¹. If Λm°(Ag⁺) = 61.9 S cm² mol⁻¹, what is Λm°(Cl⁻)?

A) 76.4 S cm² mol⁻¹

B) 61.9 S cm² mol⁻¹

C) 138.3 S cm² mol⁻¹

D) 200.2 S cm² mol⁻¹

13. Which of the following statements about the effect of temperature on conductivity is TRUE?

A) Conductivity of electrolytes decreases with increasing temperature.

B) Conductivity of electrolytes increases with increasing temperature.

C) Conductivity of electrolytes remains unaffected by temperature.

D) Conductivity of electrolytes increases with decreasing temperature.

14. The molar conductivity of an electrolyte solution is a measure of:

A) The resistance offered by the solution

B) The ability of the solution to conduct electricity per mole of electrolyte

C) The speed of the solvent molecules

D) The degree of ionization of the solvent

15. If the limiting molar ionic conductivities of K⁺ and OH⁻ are 73.5 S cm² mol⁻¹ and 198.0 S cm² mol⁻¹ respectively, what is the limiting molar conductivity of KOH?

A) 124.5 S cm² mol⁻¹

B) 271.5 S cm² mol⁻¹

C) 73.5 S cm² mol⁻¹

D) 198.0 S cm² mol⁻¹

16. Kohlrausch's law is particularly useful for determining the molar conductivity of:

A) Strong electrolytes at any concentration

B) Weak electrolytes at infinite dilution

C) Strong electrolytes at infinite dilution

D) Weak electrolytes at any concentration

17. The molar conductivity of a weak electrolyte approaches a maximum value at:

A) Zero concentration

B) Infinite concentration

C) Room temperature

D) Boiling point

18. The relationship between conductivity (κ) and resistivity (ρ) is:

A) κ = 1/ρ

B) κ = ρ

C) κ = -1/ρ

D) κ = 1/R

19. The relationship between resistance (R), resistivity (ρ), length (l), and area of cross-section (A) is given by:

A) R = ρ * (l/A)

B) R = ρ * (A/l)

C) R = (1/ρ) * (l/A)

D) R = (1/ρ) * (A/l)

20. In the context of conductance, the term 'electrolytic cell' refers to:

A) A device that produces electricity from chemical reactions.

B) A device used to measure the resistance of a solution.

C) The part of the circuit containing the electrolytic solution between two electrodes.

D) A cell used for electrolysis.

21. Which of the following methods is used to measure the conductivity of electrolytic solutions?

A) Potentiometry

B) Conductometry

C) Voltammetry

D) Polarography

22. The molar conductivity of BaCl₂ at infinite dilution is 280 S cm² mol⁻¹. If the molar conductivity of Ba²⁺ and Cl⁻ ions are 127 and 71 S cm² mol⁻¹ respectively, what is the molar conductivity of Ba²⁺ at infinite dilution?

A) 127 S cm² mol⁻¹

B) 71 S cm² mol⁻¹

C) 280 S cm² mol⁻¹

D) 153 S cm² mol⁻¹

23. Which of the following statements about the mobility of ions is INCORRECT?

A) Smaller ions have higher mobility in aqueous solutions due to less hydration.

B) Larger ions have higher mobility in non-aqueous solutions.

C) Mobility of ions increases with temperature.

D) Mobility of ions is affected by the viscosity of the solvent.

24. The transport number of an ion is defined as the fraction of the total charge carried by:

A) The electrolyte

B) The solvent

C) That particular ion

D) The electrodes

25. What happens to the conductivity of an electrolytic solution upon dilution?

A) It increases

B) It decreases

C) It remains constant

D) It can increase or decrease depending on the electrolyte

26. The relationship between conductivity (κ) and molar conductivity (Λm) is:

A) Λm = κ / C

B) Λm = 1000 * κ / C

C) Λm = κ * C

D) Λm = C / κ

27. The unit of conductance (G) is:

A) Ohm (Ω)

B) Siemens (S)

C) Farad (F)

D) Henry (H)

28. The unit of resistance (R) is:

A) Siemens (S)

B) Ohm (Ω)

C) Volt (V)

D) Ampere (A)

29. The unit of conductivity (κ) is:

A) S cm

B) S cm⁻¹

C) S cm²

D) S cm⁻²

30. Conductance of a solution is inversely proportional to:

A) Area of cross-section

B) Conductivity

C) Resistance

D) Volume

31. Conductance of a solution is directly proportional to:

A) Length of the conductor

B) Area of cross-section

C) Resistance

D) Resistivity

32. The molar conductivity of an electrolyte is defined as:

A) Conductance of solution per unit volume

B) Conductance of solution per unit concentration

C) Conductance of solution containing one mole of electrolyte

D) Conductance of solution per unit molarity

33. According to Kohlrausch's law, Λm°(CH₃COOH) = Λm°(CH₃COO⁻) + Λm°(H⁺). If Λm°(CH₃COONa) = 91.0 S cm² mol⁻¹, Λm°(HCl) = 426.16 S cm² mol⁻¹, and Λm°(NaCl) = 126.45 S cm² mol⁻¹, calculate Λm°(CH₃COOH).

A) 390.71 S cm² mol⁻¹

B) 309.71 S cm² mol⁻¹

C) 177.71 S cm² mol⁻¹

D) 108.71 S cm² mol⁻¹

34. The molar conductivity of a strong electrolyte decreases with concentration due to:

A) Decreased dissociation

B) Increased inter-ionic attraction

C) Decreased ionic mobility

D) Both B and C

35. For a weak electrolyte like acetic acid, as the concentration decreases (dilution increases):

A) Molar conductivity decreases

B) Molar conductivity increases

C) Degree of dissociation decreases

D) Conductivity increases

36. Which of the following is a measure of the ability of an ion to move in an electric field?

A) Conductivity

B) Molar conductivity

C) Ionic mobility

D) Degree of dissociation

37. The unit of cell constant is:

A) S

B) Ω

C) m⁻¹

D) Ω m

38. Conductivity (κ) is defined as the conductance of:

A) A solution of unit volume

B) A solution of unit concentration

C) A solution of unit molarity

D) A solution of unit molar conductivity

39. Conductance (G) is the reciprocal of:

A) Resistivity (ρ)

B) Resistance (R)

C) Conductivity (κ)

D) Molar conductivity (Λm)

40. The molar conductivity of a 0.1 M solution of KCl is 12.95 S cm² mol⁻¹. If the limiting molar conductivity of KCl is 149.9 S cm² mol⁻¹, what is the degree of dissociation?

A) 0.086

B) 0.1295

C) 0.86

D) 0.1499

41. Which ion has the highest ionic mobility in aqueous solution?

A) Li⁺

B) Na⁺

C) K⁺

D) Cs⁺

42. The limiting molar conductivity of NaCl, Na⁺, and Cl⁻ are 126.4, 50.1, and 71.4 S cm² mol⁻¹ respectively. What is the limiting molar conductivity of HCl?

A) 197.8 S cm² mol⁻¹

B) 121.5 S cm² mol⁻¹

C) 50.1 S cm² mol⁻¹

D) 71.4 S cm² mol⁻¹

43. Molar conductivity increases with the dilution for:

A) Strong electrolytes only

B) Weak electrolytes only

C) Both strong and weak electrolytes

D) Neither strong nor weak electrolytes

44. The degree of dissociation of a weak electrolyte at a given concentration can be determined using:

A) Ohm's Law

B) Kohlrausch's Law

C) Faraday's Laws

D) Arrhenius Equation

45. Kohlrausch's law is applicable at:

A) Finite dilution

B) Infinite dilution

C) Any concentration

D) Very low temperature

46. According to Kohlrausch's law, the molar conductivity of an electrolyte at infinite dilution is equal to the sum of:

A) The mobilities of the ions

B) The ionic conductances of the ions

C) The number of ions

D) The charge on the ions

47. Molar conductivity of a strong electrolyte at infinite dilution is represented by:

A) Λm

B) Λm°

C) κ

D) G

48. Which of the following factors affects the conductivity of an electrolytic solution?

A) Nature of electrolyte

B) Concentration of electrolyte

C) Temperature

D) All of the above

49. What is the SI unit of molar conductivity?

A) S m mol⁻¹

B) S cm mol⁻¹

C) S m² mol⁻¹

D) S cm² mol⁻¹

Conductance in electrolytic solutions molar conductivities and Kohlrausch's law - Question Bank