Advertisements
Advertisements
प्रश्न
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.
Advertisements
उत्तर
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:
Λ0 (HCl) + Λ0 (CH3COONa) - Λ0 (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` = Λ0 (CH3COONa)
Thus, Λ0 (CH3COONa) = Λ0 (HCl) + Λ0 (CH3COONa) - Λ0 (NaCl).
Because Λ0 values of strong electrolytes, HCl, CH3COONa and NaCl, can be determined by extrapolation method, the Λ0 of acetic acid can be obtained.
APPEARS IN
संबंधित प्रश्न
0.05 M NaOH solution offered a resistance of 31.6 Ω in a conductivity cell at 298 K. If the cell constant of the cell is 0.367 cm-1, calculate the molar conductivity of NaOH solution.
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 brief.
Explain the effect of dilution of the solution on conductivity.
Kohlrausch law is applicable for the solution _______.
SI unit of conductivity is _______.
Write applications of Kohlrausch’s Law.
Write three important steps required to determine molar conductivity.
The CORRECT unit of molar conductivity 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 cm2 respectively?
The molar conductances at infinite dilution `(∧_0)` for electrolytes B+A− and C+A− are 140 and 120 S cm2 mol−1. The molar conductance at infinite dilution for B+X− is 198 S cm2 mol−1. The `∧_0` (in S cm2 mol−1) of C+X− is __________.
Conductivity of KCI solution is 0.0027 Ω−1 m−1 at 25°C. The resistance of the solution is 82.4 Ω. The cell constant is ____________ m−1.
The SI unit of resistivity and molar conductivity are respectively ____________.
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?
In 2 hours, a certain current liberates 0.504 g hydrogen. How many grams of copper can be deposited by the same current flowing for the same time in a CuSO4 solution?
(Molar mass of Cu = 63.5 g mol−1, H2 = 2.0 g mol−1)
What is the cell constant of `"N"/10 "KCl"` solution at 25°C, if conductivity and resistance of a solution is 0.0112 Ω−1 cm−1 and 55.0 Ω respectively?
Conductivity of a conductor is ____________.
A conductivity cell dipped in 0.01 M AgNO3 solution gives a resistance of 3160 ohms. If cell constant is 0.47 cm−1, what is the conductivity of AgNO3 solution?
What is the unit of electrical conductance?
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?
A conductivity cell dipped in 0.5 M KCl gives a resistance of 250 ohms. If the conductivity of KC I solution is 6.68 × 10-3 S cm-1, what is the cell constant?
If the resistivity of 0.1 M KCI solution is 50 Ω cm, what is it's molar conductivity?
The value of [H3O+] in mol lit–1 of 0.001 M acetic acid solution (Ka = 1.8 × 10–5) is ______.
What is the SI unit of conductivity?
Molar conductivities at infinite dilution of Mg2+ and Br- are 105.8 Ω-1 cm2 mol-1 and 78.2 Ω-1 cm2 mol-1 respectively. Calculate molar conductivity at zero concentration of MgBr2.
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?
Explain the determination of molar conductivity of a weak electrolyte at infinite dilution or zero concentration using Kohlrausch's law.
Write the relation between molar conductivity and molar ionic conductivities for the electrolytes:
- Na2SO4
- AlCl3
