Advertisements
Advertisements
Question
The conductivity of 0.20 mol L−1 solution of KCl is 2.48 × 10−2 S cm−1. Calculate its molar conductivity and degree of dissociation (α). Given λ0 (K+) = 73.5 S cm2 mol−1 and λ0 (C1−) = 76.5 S cm2 mol−1.
Advertisements
Solution
Conductivity of KCl solution = 2.48×10–2 S cm–1
Concentration of KCl solution = 0.20 mol L–1
= 0.20 × 1000 mol cm–3
= 200 mol cm–3
Molar conductivity
`Lambda_m=k/c`
`=(2.48xx10^(-2)" S "cm^(-1))/(200" mol "cm^(-3))`
`=124xx10^(-6)" S "cm^2" mol"^(-1)`
Given:
`lambda_(K^+)^@=73.5" S "cm^2" mol"^(-1)`
`lambda_(Cl^-)^@=76.5" S "cm^2" mol"^(-1)`
Degree of dissociation
`alpha=Lambda_m/Lambda_m^@" "" "" "" ".......("i")`
`Lambda_(m(KCl))^@=lambda_(K+)^@+lambda_(Cl^-)^@`
`=73.5+76.5`
`=150" S "cm^2" mol"^(-1)`
`"Substituting the values of "Lambda_m" and "Lambda_(m(KCl))^@" in (i), we get"`
`alpha=(124xx10^(-6)" S "cm^2" mol"^(-1))/(150" S "cm^2" mol"^(-1))=0.82xx10^(-6)`
RELATED QUESTIONS
Conductivity of 0.00241 M acetic acid is 7.896 × 10−5 S cm−1. Calculate its molar conductivity and if `Lambda_m^0` for acetic acid is 390.5 S cm2 mol−1, what is its dissociation constant?
Kohlrausch law of independent migration of ions states ____________.
\[\ce{\Lambda^0_m(NH4OH)}\] is equal to ______.
Molar conductivity of ionic solution depends on:
(i) temperature.
(ii) distance between electrodes.
(iii) concentration of electrolytes in solution.
(iv) surface area of electrodes.
When acidulated water (dil.H2SO4 solution) is electrolysed, will the pH of the solution be affected? Justify your answer.
Assertion: Copper sulphate can be stored in zinc vessel.
Reason: Zinc is less reactive than copper.
Solutions of two electrolytes ‘A’ and ‘B’ are diluted. The Λm of ‘B’ increases 1.5 times while that of A increases 25 times. Which of the two is a strong electrolyte? Justify your answer. Graphically show the behavior of ‘A’ and ‘B’.
Assertion (A) : Conductivity decreases with decrease in concentration of electrolyte.
Reason (R) : Number of ions per unit volume that carry the current in a solution decreases on dilution.
Assertion (A): Molar conductivity decreases with increase in concentration.
Reason (R): When concentration approaches zero, the molar conductivity is known as limiting molar conductivity.
The resistance of a conductivity cell with a 0.1 M KCl solution is 200 ohm. When the same cell is filled with a 0.02 M NaCl solution, the resistance is 1100 ohm. If the conductivity of 0.1 M KCl solution is 0.0129 ohm-1 cm-1, calculate the cell constant and molar conductivity of 0.02 M NaCl solution.
