Kohlrausch's Law

IMPORTANT

Kohlrausch's Law: Overview

In the topic, we will study the law of determining molar conductivity of the electrolytes from the conductivities of cation and anion, respectively. It also mentions the applications of Kohlrausch’s law along with the examples based on this law.

Important Questions on Kohlrausch's Law

HARD
IMPORTANT

Find the solubility product of a saturated solution of Ag 2 CrO 4   at 298 K in water if the emf of the cell  Ag Ag + Ag 2 CrO 4 Ag + 0 .1 M Ag s is 0.164 V at 298 K.

MEDIUM
IMPORTANT

Form the following molar conductivities at infinite dilution,

m for Al2SO43=858 S cm2 mol-1m for NH4OH=238.3 S cm2 mol-1m for NH42SO4=238.4 S cm2 mol-1

Calculate m for AlOH3

EASY
IMPORTANT

The molar conductance of 0.01 M electrolyte is 124 ohm-1 cm2 mol-1 at 298 K. Calculate its specific conductance.

EASY
IMPORTANT

The specific conductance of 0.01 M of an electrolyte is 1.24×10-3 ohm-1 cm-1 at 298 K. Calculate the molar conductance.

EASY
IMPORTANT

Calculate the molar conductance of 0.02 M solution of an electrolyte which has a resistance of 310 ohm at 298 K. Cell constant is 0.68 cm-1.

MEDIUM
IMPORTANT

The equivalent conductivity of acetic acid at infinite dilution is 387 S cm2 eq-1. At the same temperature, for 0.001 M solution of acetic acid, it is 55 S cm2 eq-1. What is the degree of dissociation of 0.1 N acetic acid? Assume 1-α1

A : 1.5%B : 1.35%C : 2%

Enter your correct answer as A, B or C.

HARD
IMPORTANT

If the value of molar conductivities at infinite dilution for CH3COOHHCl and NaCl are 390.5, 425.4 and 126.4 S cm2mol-1 respectively at 298 K. Calculate the molar conductivity at infinite dilution of CH3COONa in S cm2mol-1. (Just mention the value, no requirement of units in the answer).

MEDIUM
IMPORTANT

Define limiting molar conductivity Λ°m.

HARD
IMPORTANT

What is the molar conductivity of AgI at zero concentration if the 0 values of NaI, AgNO3 and NaNO3 are respectively 126.9 Ω-1cm2mol-1133.4 Ω-1cm2mol-1, 121.5 Ω-1cm2mol-1?

HARD
IMPORTANT

How is the molar conductivity of strong electrolytes at zero concentration determined by graphical method? Why is this method not useful for weak electrolytes?

HARD
IMPORTANT

The molar conductivities at zero concentrations of NH4Cl, NaOH and NaCl are respectively 149.7Ω-1cm2mol-1, 248.1Ω-1cm2mol-1 and 126.5Ω-1cm2mol-1. What is the molar conductivity of NH4OH at zero concentration?

MEDIUM
IMPORTANT

What will be the calculated value of standard electrode potential(E0) Cl-/AgCl/Ag at 298 K temperature, if solubility of silver chloride (AgCl) in 0.05 M BaCl2 is nearly 10-9 M (E0 Ag/Ag+=0.80 volts).

HARD
IMPORTANT

Which of the following graph is/are correct for a weak acid (HA), where symbols have usual meaning?

HARD
IMPORTANT

The equivalent conductance of 1M benzoic acid is 12.8 ohm-1cm2 and if the conductance of benzoate ion and H+ ion at infinite dilution are 42 and 288.42ohm-1cm2 respectively. Calculate percentage of degree of dissociation.
Report your answer by rounding upto nearest whole number.

EASY
IMPORTANT

If molar conductivity of Ca2+ and Cl- ions are 119 and 71S cm2mol-1 respectively, then the molar conductivity of CaCl2 at infinite dilution is

EASY
IMPORTANT

The graph of C m for an aqueous solution of which substance is not obtained as a straight line?

HARD
IMPORTANT

Stufy the following cell reaction:

Pbs+Hg2SO4s PbSO4s+2Hgl

Ecell°= 0.92 V

Ksp  PbSO4=2 × 108, Ksp Hg2SO4=1 × 106

Calculate the Ecell for a cell containing saturated solutions of these two salts at their respective electrodes:

Given [antilog ( 0.141 )=1.38 ]

HARD
IMPORTANT

At 298 K , the conductivity of a saturated solution of AgCl in water is 2.6 × 106ohm1 cm1  . Given ,λmAg+=63 ohm1 cm2 mol1 & λmCl=67 ohm1 cm2 mol1

Therefore solubility product of AgCl is

HARD
IMPORTANT

The specific conductivity of a saturated solution of AgCl is 3.4 × 1 0 - 6 S cm - 1  at 25oC. If λ Ag + = 62.3 S cm 2 mol - 1 , λ Cl - = 67.7 S cm 2 mol - 1 , solubility of AgCl at 25oC is

HARD
IMPORTANT

The conductivity 0.001 M Na2SO4 solution is 2.6×10-4 S cm-1 and increases to 7.0×10-4 S cm-1, when the solution is saturated with CaSO4. The molar conductivities of Na+ and Ca+ are 50 and 120 S cm2 mol-1, respectively. Neglect conductivity of the water used. What is the solubility product of CaSO4?