Advertisements
Advertisements
Question
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
Solution
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
RELATED QUESTIONS
The molar conductivity of 0.05 M BaCl2 solution at 25° C is 223Ω-1 cm2 mol-1. What is its conductivity?
Answer the following in one or two sentences.
Write the relationship between conductivity and molar conductivity and hence unit of molar conductivity.
Answer the following in brief.
Explain the effect of dilution of the solution on conductivity.
SI unit of conductivity is _______.
In case of weak electrolyte the graph Λ vs `sqrt"c"` is _______.
Give SI unit of resistivity.
Write relation between electrolytic conductivity and molar conductivity.
If resistivity of 0.8 M KCI solution is 2.5 × 10-3 Ω cm. Calculate molar conductivity of solution?
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 resistance of `1/10`M solution is 2.5 × 103 ohm. What is the molar conductivity of solution? (cell constant = 1.25 cm-1).
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?
The SI unit of resistivity and molar conductivity are respectively ____________.
The molar conductivities at infinite dilution for sodium acetate, HCI and NaCl are 91 S cm2 mol-1, 425.9 S cm2 mol-1 and 126.4 S cm2 mol-1 respectively. The molar conductivity of acetic acid at infinite dilution is ______.
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)
Which of the following graph represents the variation of `∧` with `sqrt"c"` for acetic acid solution?
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 cm2 respectively?
What is the SI unit of conductivity?
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?
Specific conductance of 0.1 M HNO3 is 6.3 × 10−2 ohm−1 cm−1. The molar conductance of the solution is ______.
When electric current is passed through acidified water, 112 mL of hydrogen gas at STP collected at the cathode in 965 seconds. The current passed in amperes is ______.
Which of the following expressions correctly represents molar conductivity?
The molar conductivity of a 0.02 mol dm−3 solution of sodium hydroxide is 230.5 Ω−1 cm2 mol−1. What is its conductivity?
