Answer the following: What is Kohlrausch law of independent migration of ions? How is it useful in obtaining molar conductivity at zero concentration of a weak electrolyte? Explain with an example. - Chemistry

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Answer the following:

What is Kohlrausch law of independent migration of ions? How is it useful in obtaining molar conductivity at zero concentration of a weak electrolyte? Explain with an example.



1) Kohlrausch law states that “at infinite dilution each ion migrates independent of co-ion and contributes to total molar conductivity of an electrolyte irrespective of the nature of other ions to which it is associated.”

2) Both cation and anion contribute to molar conductivity of the electrolyte at zero concentration and thus ∧0 is the sum of molar conductivity of cation and that of the anion at zero concentration.

Thus, Λ0 `= "n"_+lambda_+^0 + "n"_(_) lambda_(-)^0`

where λ+ and λ_ are molar conductivities of cation and anion, respectively, n+ and n are the number of moles of cation and anion specified in the chemical formula of the electrolyte.

3) Determination of molar conductivity of weak electrolyte at zero concentration:
The theory is particularly useful in calculating ∧0 values of weak electrolytes from those of strong electrolytes.

For example, ∧0 of acetic acid can be calculated by knowing those of HCl, NaCl and CH3COONa as described below:

Λ(HCl) + Λ(CH3COONa) - Λ(NaCl)

`= lambda_("H"^+)^0 + lambda_("Cl"^-)^0 + lambda_("CH"_3"COO"^-)^0 + lambda_("Na"^+)^0 - lambda_("Na"^+)^0 - lambda_("Cl"^-)^0`

`= lambda_("H"^+)^0 + lambda_("CH"_3"COO"_-)^0` = Λ(CH3COONa)

Thus, Λ(CH3COONa) = Λ(HCl) + Λ(CH3COONa) - Λ(NaCl).

Because Λvalues of strong electrolytes, HCl, CH3COONa and NaCl, can be determined by extrapolation method, the Λ0 of acetic acid can be obtained.

Concept: Electrical Conductance of Solution
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Chapter 5: Electrochemistry - Exercises [Page 118]


Balbharati Chemistry 12th Standard HSC for Maharashtra State Board
Chapter 5 Electrochemistry
Exercises | Q 4.01 | Page 118


The molar conductivity of 0.05 M BaCl2 solution at 25° C is 223Ω-1 cm2 mol-1. What is its conductivity?

Choose the most correct option.

Two solutions have the ratio of their concentrations 0.4 and ratio of their conductivities 0.216. The ratio of their molar conductivities will be ______.

What is a cell constant? What are its units? How is it determined experimentally?

Answer the following in one or two sentences.

Write the relationship between conductivity and molar conductivity and hence unit of molar conductivity.

Kohlrausch law is applicable for the solution _______.

SI unit of conductivity is _______.

In case of weak electrolyte the graph Λ vs `sqrt"c"` is _______.

The molar conductivity and conductivity of AgNO3 solution is 121.4 Ω–1 cm2 mol–1 and 2.428 × 10–3 Ω–1 cm–1 at 25 °C. What is molar concentration of AgNO3 solution?

Give SI unit of resistivity.

Write an equation that shows the relationship between molar conductivity and degree of dissociation of weak electrolyte.

Write applications of Kohlrausch’s Law.

State Kohlrausch law of independent migration of ions.

Write three important steps required to determine molar conductivity.

Calculate molar conductivities at zero concentration for CaCl2 and NaCl.

Given: molar ionic conductivities of Ca2+, Cl, Na+ ions are respectively, 104, 76.4, 50.1 Ω–1 cm–2 mol–1

If resistivity of 0.8 M KCI solution is 2.5 × 10-3 Ω cm. Calculate molar conductivity of solution?

A conductivity cell having cell constant 8.76 cm−1, placed in 0.01 M solution of an electrolyte offered a resistance of 1000 ohms. What is the specific conductance of electrolytes?

Which among the following solution has the highest conductivity (k) value?

The resistance of a conductivity cell containing 0.001 M KCl solution at 298 K is 1500 Ω. What is the cell constant if conductivity of 0.001 M KCI solution at 298 K is 0.146 × 10−3 S cm−1?

Which of the following graph represents the variation of `∧` with `sqrt"c"` for acetic acid solution?

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What is the relation between cell constant, conductivity and electrical resistance?

Conductivity of a conductor is ____________.

What will be the concentration of NaCl solution, if the molar conductivity and conductivity of NaCl solution is 124.3 Ω-1 cm2 mol-1 and 1.243 × 10-4 Ω-1 cmrespectively?

What is the conductivity of 0.01 M NaCl solution if resistance and cell constant of NaCl solution are 375 ohms and 0.5 cm-1 respectively at 298 K?

The value of [H3O+] in mol lit–1 of 0.001 M acetic acid solution (Ka = 1.8 × 10–5) is ______.

Calculate molar conductivity for 0.5 M BaCl2 if its conductivity at 298K is 0.01 Ω–1 cm–1.

A conductivity cell filled with 0.02 M AgNO3 gives at 25°C resistance of 947 ohms. If the cell constant is 2.3 cm-1, what is the molar conductivity of 0.02 M AgNO3 at 25°C?

What is the SI unit of molar conductivity?

Define cell constant. Give its units.

Write the relation between molar conductivity and molar ionic conductivities for the electrolytes:

  1. Na2SO4
  2. AlCl3


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