Electrochemistry NEET Previous Year Questions with Answer

Q 1 :
If the molar conductivity $(Λ_{m})$ of a 0.050 mol $L^{- 1}$ solution of a monobasic weak acid is 90 S ${cm}^{2}$ ${mol}^{- 1}$ , its extent (degree) of dissociation will be

$[Assume Λ_{+}^{\circ} = 349.6 {S cm}^{2} {mol}^{- 1} and Λ_{-}^{\circ} = 50.4 {S cm}^{2} {mol}^{- 1}]$ [2025]

0.225
0.215
0.115
0.125

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(1)

Given: Concentration of solution = 0.050 mol $L^{- 1}$

$Λ_{m} = 90 {S cm}^{2} {mol}^{- 1}$

$Λ_{m}^{o} = Λ_{+}^{o} + Λ_{-}^{o}$

$= 349.6 + 50.4 = 400 {S cm}^{2} {mol}^{- 1}$

$α = \frac{Λ_{m}}{Λ_{m}^{o}} = \frac{90}{400} = 0.225$

Q 2 :
Molar conductance of an electrolyte increases with dilution according to the equation:

$Λ_{m} = Λ_{m}^{\circ} - A \sqrt{c}$

Which of the following statements are true?

(A) This equation applies to both strong and weak electrolytes.
(B) Value of the constant A depends upon the nature of the solvent.
(C) Value of constant A is same for both $B a C l_{2}$ and $M g S O_{4}$ .
(D) Value of constant A is same for both $B a C l_{2}$ and $M g {(O H)}_{2}$ .

Choose the most appropriate answer from the options given below: [2023]

(A) and (B) only
(A), (B) and (C) only
(B) and (C) only
(B) and (D) only

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(4)

The given equation is applicable only to strong electrolytes. For strong electrolytes, $Λ_{m}$ increases slowly with dilution and thus is represented by the given equation. The value of the constant 'A' for a given solvent and temperature depends on the type of electrolyte, i.e., the charge on the cation and anion produced on the dissociation of the electrolyte in the solution. Value of constant 'A' is same for both ${BaCl}_{2}$ and ${Mg(OH)}_{2}$ .

Q 3 :
The conductivity of centimolar solution of KCl at 25 ${}^{\circ}C$ is 0.0210 ${ohm}^{- 1}$ ${cm}^{- 1}$ and the resistance of the cell containing the solution at 25 ${}^{\circ}C$ is 60 ohm. The value of cell constant is [2023]

1.26 ${cm}^{- 1}$
3.34 ${cm}^{- 1}$
1.34 ${cm}^{- 1}$
3.28 ${cm}^{- 1}$

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(1)

Given, $κ = 0.0210$ ${ohm}^{- 1}$ ${cm}^{- 1}, R = 60$ $ohm$

$κ = \frac{1}{R} \times \frac{l}{a} (where \frac{l}{a} = cell constant)$

or $0.0210 = \frac{1}{60} \times \frac{l}{a}$

or $\frac{l}{a} = 60 \times 0.0210 = 1.26$ ${cm}^{- 1}$

Q 4 :
The molar conductance of NaCl, HCl and ${CH}_{3} COONa$ at infinite dilution are 126.45, 426.16 and 91.0 S ${cm}^{2}$ ${mol}^{- 1}$ respectively. The molar conductance of ${CH}_{3} COOH$ at infinite dilution is. Choose the right option for your answer. [2021]

540.48 S ${cm}^{2}$ ${mol}^{- 1}$
201.28 S ${cm}^{2}$ ${mol}^{- 1}$
390.71 S ${cm}^{2}$ ${mol}^{- 1}$
698.28 S ${cm}^{2}$ ${mol}^{- 1}$

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(3)

$Λ_{{CH}_{3} COOH}^{\infty} = Λ_{{CH}_{3} COONa}^{\circ} + Λ_{HCl}^{\circ} - Λ_{NaCl}^{\circ}$

$= 91.0 + 426.16 - 126.45$

$= 390.71$ $S$ ${cm}^{2}$ ${mol}^{- 1}$

Q 5 :
The molar conductivity of 0.007 M acetic acid is 20 S ${cm}^{2}$ ${mol}^{- 1}$ . What is the dissociation constant of acetic acid? Choose the correct option.

$[\begin{matrix} Λ_{H^{+}}^{\circ} = 350 {S cm}^{2} {mol}^{- 1} \\ Λ_{{CH}_{3} {COO}^{-}}^{\circ} = 50 {S cm}^{2} {mol}^{- 1} \end{matrix}]$ [2021]

$2.50 \times 10^{- 5}$ $mol$ $L^{- 1}$
$1.75 \times 10^{- 4}$ $mol$ $L^{- 1}$
$2.50 \times 10^{- 4}$ $mol$ $L^{- 1}$
$1.75 \times 10^{- 5}$ $mol$ $L^{- 1}$

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(4)

$Λ_{m ({CH}_{3} COOH)}^{\circ} = λ_{H^{+}}^{\circ} + λ_{{CH}_{3} {COO}^{-}}^{\circ}$

$= 350 + 50 = 400$ $S$ ${cm}^{2}$ ${mol}^{- 1}$

Degree of dissociation, $α = \frac{Λ_{m}^{c}}{Λ_{m}^{o}} = \frac{20}{400} = 0.05$

So, dissociation constant, $K_{a} = c α^{2} (for weak electrolytes)$

$= 0.007 {(0.05)}^{2} = 1.75 \times 10^{- 5}$ $mol$ $L^{- 1}$

Q 6 :
Following limiting molar conductivities are given as:

$λ_{m (H_{2} {SO}_{4})}^{\circ} = x$ $S$ ${cm}^{2}$ ${mol}^{- 1}$

$λ_{m (K_{2} {SO}_{4})}^{\circ} = y$ $S$ ${cm}^{2}$ ${mol}^{- 1}$

$λ_{m ({CH}_{3} COOK)}^{\circ} = z$ $S$ ${cm}^{2}$ ${mol}^{- 1}$

$λ_{m}^{\circ} (in$ $S$ ${cm}^{2}$ ${mol}^{- 1})$ ${for CH}_{3} COOH will be$ [2019]

$x - y + 2 z$
$x + y - z$
$x - y + z$
$\frac{(x - y)}{2} + z$

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(4)

According to Kohlrausch's law,

$Λ_{m}^{o} {for CH}_{3} COOH = λ_{{CH}_{3} {COO}^{-}}^{\circ} + λ_{H^{+}}^{\circ}$

$Λ ° {for H}_{2} {SO}_{4} = 2 λ_{H^{+}}^{\circ} + λ_{{SO}_{4}^{2 -}}^{\circ} = x$ $S$ ${cm}^{2}$ ${mol}^{- 1}$ ...(i)

$Λ ° {for K}_{2} {SO}_{4} = 2 λ_{K^{+}}^{\circ} + λ_{{SO}_{4}^{2 -}}^{\circ} = y$ $S$ ${cm}^{2}$ ${mol}^{- 1}$ ...(ii)

$Λ ° {for CH}_{3} COOK = λ_{{CH}_{3} {COO}^{-}}^{\circ} + λ_{K^{+}}^{\circ} = z$ $S$ ${cm}^{2}$ ${mol}^{- 1}$ ...(iii)

On adding equation (i) and 2 $\times$ (iii) and subtracting (ii), we get

$2 λ_{H^{+}}^{\circ} + λ_{{SO}_{4}^{2 -}}^{\circ} + 2 λ_{{CH}_{3} {COO}^{-}}^{\circ} + 2 λ_{K^{+}}^{\circ} - 2 λ_{K^{+}}^{\circ} - λ_{{SO}_{4}^{2 -}}^{\circ} = x + 2 z - y$

$2 λ_{H^{+}}^{\circ} + 2 λ_{{CH}_{3} {COO}^{-}}^{\circ} = x + 2 z - y$

$λ_{H^{+}}^{\circ} + λ_{{CH}_{3} {COO}^{-}}^{\circ} = \frac{(x - y)}{2} + z$

Q 7 :
The molar conductivity of a 0.5 $mol / {dm}^{3}$ solution of ${AgNO}_{3}$ , with electrolytic conductivity of 5.76 $\times 10^{- 3}$ $S$ ${cm}^{- 1}$ at 298 K is [2016]

2.88 S ${cm}^{2} / mol$
11.52 S ${cm}^{2} / mol$
0.086 S ${cm}^{2} / mol$
28.8 S ${cm}^{2} / mol$

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(2)

$Λ_{m} = \frac{κ \times 1000}{Molarity (M)}$

$= \frac{5.76 \times 10^{- 3} {S cm}^{- 1} \times 1000}{0.5 {mol cm}^{- 3}} = 11.52$ $S$ ${cm}^{2}$ ${mol}^{- 1}$

Topic Question Set

Q 1 :
If the molar conductivity $(Λ_{m})$ of a 0.050 mol $L^{- 1}$ solution of a monobasic weak acid is 90 S ${cm}^{2}$ ${mol}^{- 1}$ , its extent (degree) of dissociation will be

$[Assume Λ_{+}^{\circ} = 349.6 {S cm}^{2} {mol}^{- 1} and Λ_{-}^{\circ} = 50.4 {S cm}^{2} {mol}^{- 1}]$ [2025]

Q 3 :
The conductivity of centimolar solution of KCl at 25 ${}^{\circ}C$ is 0.0210 ${ohm}^{- 1}$ ${cm}^{- 1}$ and the resistance of the cell containing the solution at 25 ${}^{\circ}C$ is 60 ohm. The value of cell constant is [2023]

Q 4 :
The molar conductance of NaCl, HCl and ${CH}_{3} COONa$ at infinite dilution are 126.45, 426.16 and 91.0 S ${cm}^{2}$ ${mol}^{- 1}$ respectively. The molar conductance of ${CH}_{3} COOH$ at infinite dilution is. Choose the right option for your answer. [2021]

Q 7 :
The molar conductivity of a 0.5 $mol / {dm}^{3}$ solution of ${AgNO}_{3}$ , with electrolytic conductivity of 5.76 $\times 10^{- 3}$ $S$ ${cm}^{- 1}$ at 298 K is [2016]

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Topic Question Set

Q 1 : If the molar conductivity (Λm) of a 0.050 mol L-1 solution of a monobasic weak acid is 90 S cm2 mol-1, its extent (degree) of dissociation will be [Assume Λ+∘=349.6 S cm2 mol-1 and Λ-∘=50.4 S cm2 mol-1] [2025]

Q 3 : The conductivity of centimolar solution of KCl at 25 C∘ is 0.0210 ohm-1 cm-1 and the resistance of the cell containing the solution at 25C∘ is 60 ohm. The value of cell constant is [2023]

Q 4 : The molar conductance of NaCl, HCl and CH3COONa at infinite dilution are 126.45, 426.16 and 91.0 S cm2 mol-1 respectively. The molar conductance of CH3COOH at infinite dilution is. Choose the right option for your answer. [2021]

Q 5 : The molar conductivity of 0.007 M acetic acid is 20 S cm2 mol-1. What is the dissociation constant of acetic acid? Choose the correct option. [ΛH+∘=350 S cm2 mol-1ΛCH3COO-∘=50 S cm2 mol-1] [2021]

Q 6 : Following limiting molar conductivities are given as: λm(H2SO4)∘=x S cm2 mol-1 λm(K2SO4)∘=y S cm2 mol-1 λm(CH3COOK)∘=z S cm2 mol-1 λm∘ (in S cm2 mol-1) for CH3COOH will be [2019]

Q 7 : The molar conductivity of a 0.5 mol/dm3 solution of AgNO3, with electrolytic conductivity of 5.76 ×10-3 S cm-1 at 298 K is [2016]

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Q 1 :
If the molar conductivity $(Λ_{m})$ of a 0.050 mol $L^{- 1}$ solution of a monobasic weak acid is 90 S ${cm}^{2}$ ${mol}^{- 1}$ , its extent (degree) of dissociation will be

$[Assume Λ_{+}^{\circ} = 349.6 {S cm}^{2} {mol}^{- 1} and Λ_{-}^{\circ} = 50.4 {S cm}^{2} {mol}^{- 1}]$ [2025]

Q 3 :
The conductivity of centimolar solution of KCl at 25 ${}^{\circ}C$ is 0.0210 ${ohm}^{- 1}$ ${cm}^{- 1}$ and the resistance of the cell containing the solution at 25 ${}^{\circ}C$ is 60 ohm. The value of cell constant is [2023]

Q 4 :
The molar conductance of NaCl, HCl and ${CH}_{3} COONa$ at infinite dilution are 126.45, 426.16 and 91.0 S ${cm}^{2}$ ${mol}^{- 1}$ respectively. The molar conductance of ${CH}_{3} COOH$ at infinite dilution is. Choose the right option for your answer. [2021]

Q 7 :
The molar conductivity of a 0.5 $mol / {dm}^{3}$ solution of ${AgNO}_{3}$ , with electrolytic conductivity of 5.76 $\times 10^{- 3}$ $S$ ${cm}^{- 1}$ at 298 K is [2016]