Kohlrausch's Law and its Application

IMPORTANT

Kohlrausch's Law and its Application: Overview

This topic covers concepts such as Equivalent Conductivity at Infinite Dilution, Kohlrausch's Law, Applications of Kohlrausch's Law, Determination of Molar Conductivity of a Weak Electrolyte at Given Concentration, etc.

Important Questions on Kohlrausch's Law and its Application

EASY
IMPORTANT

What is limiting molar conductivity of ions?

EASY
IMPORTANT

The molar conductance and the specific conductance of an electrolyte are related by the formula

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.

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).

HARD
IMPORTANT

The molar conductivity of a solution of a weak acid HX (0.01 M) is 10 times smaller than the molar conductivity of a solution of a weak acid HY (0.10 M). If λ°X-=λ°Y-, the difference in their pKa values, pKa(HX)-pKa(HY), is (consider degree of ionization of both acids to be <<1)

HARD
IMPORTANT

Λ°m for NaCl, HCl and NaAc are 126.4, 425.9 and 91.0 S cm2 mol-1 respectively. Calculate Λ°m for HAc.

MEDIUM
IMPORTANT

Define limiting molar conductivity Λ°m.

MEDIUM
IMPORTANT

What is meant by limiting molar conductance ?

MEDIUM
IMPORTANT

The molar conductivity of 0.025 mol L-1 methanoic acid is 46.1 S cm2 mol-1. Calculate the degree of dissociation. Given : λ°(H+)=349.6 S cm2 mol-1λ°(HCOO-)=54.6 S cm2 mol-1.

MEDIUM
IMPORTANT

The molar conductivities at infinite dilution for CH3COONa, HCl and NaCl are 91.0, 425.9 and 126.4 S cm2 mol-1 respectively at 298K. Calculate the molar conductivities of CH3COOH at infinite dilution.

MEDIUM
IMPORTANT

State Kohlrausch law of independent migration of ions. Why does the conductivity of a solution decrease with dilution?

HARD
IMPORTANT

Consider the galvanic cell, Pt(s)H2(1 bar)HCl(aq)(1 M)Cl(1 bar)Pt(s). After running the cell for sometime, the concentration of the electrolyte is automatically raised to 3 M HCl. Molar conductivity of the 3 M HCl is about 240 S cm2 mol-1 and limiting molar conductivity of HCl is about 420 S cm2mol-1. If Kb of water is 0.52 K kg mol-1, calculate the boiling point of the electrolyte at the end of the experiment.

HARD
IMPORTANT

At 25°C the molar conductance of 0.007 M hydrofluoric acid is 150 mho cm2 mol-1 and its Λ°m=500 mho cm2 mol-1. The value of the dissociation constant of the acid at the given concentration at 25°C is

HARD
IMPORTANT

Equivalent conductivity at infinite dilution for sodium- potassium oxalate [(COO-)2Na+K+)] will be [ given : molar conductivities of oxalate, K+ and Na+ ions at infinite dilution are 148.2, 50.1, 73.5 S cm2 mol-1, respectively].

MEDIUM
IMPORTANT

The equivalent conductance of M/32 solution of a weak monobasic acid is 8 mho cm2 and at infinite dilution is 400 mho cm2. The dissociation constant of this acid is

HARD
IMPORTANT

The ionization constant of a weak electrolyte is 2.5 × 10-5, and molar conductance of its 0.01 M solution is 19.6 S cm2 mol-1. The molar conductance at infinite dilution ( S cm2 mol-1) is:

HARD
IMPORTANT

The values of limiting ionic conductance of H+ and HCOO- ions are respectively 347 and 53 S cm2 mol-1 at 298 K. If the molar conductance of 0.025 M methanoic acid at 298 K is 40 S cm2 mol-1, the dissociation constant of methanoic acid at 298 K is:

HARD
IMPORTANT

The limiting molar conductivities of HCl, CH3COONa and NaCl are respectively 425, 90 and 125 mho cm2 mol-1 at 25C. The molar conductivity of 0.1 M CH3COOH solution is 7.8 mho cm2 mol-1 at the same temperature. The degree of dissociation of 0.1 M acetic acid solution at the same temperature is