Electrochemistry Test

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Electrochemistry Test - 26

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Weekly Quiz Competition

Question 1
1 / -0

Conductivity of a solution depends upon:

A
Nature of electrolyte

B
Nature of solvent

C
Temperature

D
All of the above

Solution

The conductance of a solution depends upon its dilution, no. of ions present in solution. nature of solvent and nature of solute.
For example, with increases in dilution, the number of ions present in the solution increases and the conductance of the solution increases.
Question 2
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Limiting Ionic conductivity is defined as:

A
Conducting power of one gram of ions at a given temperature and concentration

B
Conducting power of one mole of electrolyte at a given temperature and concentration

C
Conducting power of one mole of ions at a given temperature at infinite dilution

D
Conducting power of one gram mole of ions at a given temperature and concentration

Solution

The correct answer is option A
The molar conductivity of a solution at infinite dilution is known as limiting molar conductivity. In other words, When the concentration of the electrolyte approaches zero, the molar conductivity is known as limiting molar conductivity.
Question 3
1 / -0

Which of the following statements is correct?

A
Molar conductivity of a strong electrolyte decreases with dilution

B
Molar conductivity of a strong and weak electrolyte decreases with dilution

C
Molar conductivity of a weak electrolyte decreases with dilution

D
Molar conductivity of a strong and weak electrolyte increases with dilution

Solution

The correct answer is Option D.

The molar conductivity increases with decrease in concentration both, for weak and strong electrolytes.

This is because the total volume, V, of a solution containing one mole of electrolyte also increases. It has been found that a decrease in k on dilution of a solution is more than compensated by an increase in its volume.
Question 4
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Molar conductivity for a compound AB is 145.0 Scm²mol^-1 and for CB is 110.1 Scm²mol^-1. Limiting molar conductivity for A⁺ is 73.5 Scm²mol^-1. What is limiting molar conductivity for C⁺?

A
326.6 S cm² mol^-1

B
38.6 S cm² mol^-1

C
181.6 S cm² mol^-1

D
90.8 S cm² mol^-1

Solution

The correct answer is Option B.
Λ_m of AB = 145.05 cm²mol^-1
Λ_m of AB = Λ^oA + Λ^oB (Kohlraush’s law)
145 = Λ^oA + Λ^oB --- (1)
Λ_m of CB = 110.10 Scm²mol^-1
Λ_m of CB = Λ^oC + Λ^oB
110.1 = Λ^oC + Λ^oB --- (2)
Eqn (1) - Eqn (2)

145 - 110.1 = Λ^oA + Λ^oB - Λ^oC + Λ^oB
34.9 = Λ^oA - Λ^oC
34.9 = 73.5 - Λ^oC
Λ^oC = 73.5 - 34.9
= 38.6 Scm²mol^-1
Question 5
1 / -0

Kohlrausch’s Law shows that:

A
at infinite dilution the ionic conductivity of ions is additive.

B
at infinite dilution the ionic conductivity of all the ions of the electrolyte become equal.

C
at infinite dilution the concentration of the electrolyte becomes unity.

D
at infinite dilution the concentration of ions increases.

Solution

The correct answer is option A
Kohlrausch's law states that the equivalent conductivity of an electrolyte at infinite dilution is equal to the sum of the conductances of the anions and cations. If a salt is dissolved in water, the conductivity of the solution is the sum of the conductances of the anions and cations.
Hence, at infinite dilution the ionic conductivity of ions is additive.
Question 6
1 / -0

Conductivity of a solution contained within 1 centimetre cube volume is known as:

A
Resistance

B
Molar conductivity

C
Conductivity

D
Conductance

Solution

The correct answer is option C
Conductivity of a solution is equal to the conductance of a solution of 1cm length and cross section area of 1 square cm it may also be defined as the conductance of one centimeter cube of the conductor .It is represented by the symbol kappa (k) mathematically we can write
K = G×G⋅ conductance ,G⋅=cell constant
The unit of K is ohm−1cm−1 or S cm−1
The conductivity K of an electrolytic solution depends on the concentration of the electrolyte nature of solvent and temperature .molar conductivity molar conductivity of a solution at a given concentration is the conductance of the volume v of solution containing one mole of electrolyte between two electrodes with area of cross section a and distance of unit length.
Question 7
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Kohlrausch’s Law is applicable:

A
to aqueous solution of strong electrolytes

B
applicable to electrolytes dissolved in a solvent of low polarity only.

C
to electrolytes at temperature above room temperature.

D
to electrolytic solutions at infinite dilution

Solution

The correct answer is Option D.

Kohlrausch's law states that the equivalent conductivity of an electrolyte at infinite dilution is equal to the sum of the conductances of the anions and cations. When the concentration of the electrolyte approaches zero, the molar conductivity is known as limiting molar conductivity, Ëm°
Question 8
1 / -0

At 300K molar conductivity of solution A is 350 units, and at infinite dilution the molar conductivity of the same sample is 480 unit. Predict the percentage dissociation of the electrolyte.

A
73.0%

B
37.0%

C
63.0%

D
137.0%

Solution
Question 9
1 / -0

For weak electrolytes ∧m^o cannot to be calculated by extrapolation of ∧m^o vs (c)^1/2graph. Which of the following is not the reason?

A
∧m⁰ increases steeply on dilution especially near lower concentrations.

B
Weak electrolytes ionize completely in solution

C
∧m for weak electrolytes does not vary linearly with dilution.

D
Weak electrolytes dissociated to a much lesser extent as compared to strong electrolytes and therefore, ∧m⁰ of weak electrolytes is low. It becomes even low at lower concentration.

Solution

The correct answer is option B
In case of the weak electrolyte it is not possible to calculate the molar conductivity at infinite dilution by extrapolation of the graph between the molar conductivity and the concentration,because there is large variation between them. As you can see from the graph:-

In case of weak electrolytes conductivity can be calculated by Kohlrausch law.
Question 10
1 / -0

With increase in temperature the degree of dissociation of electrolyte:

A
Increases

B
Depends on the enthalpy change of dissolution

C
Decreases

D
Depends on the nature of salt

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Electrochemistry Test - 26

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Question 1

Nature of electrolyte

Nature of solvent

Temperature

All of the above

Solution

Question 2

Conducting power of one gram of ions at a given temperature and concentration

Conducting power of one mole of electrolyte at a given temperature and concentration

Conducting power of one mole of ions at a given temperature at infinite dilution

Conducting power of one gram mole of ions at a given temperature and concentration

Solution

Question 3

Molar conductivity of a strong electrolyte decreases with dilution

Molar conductivity of a strong and weak electrolyte decreases with dilution

Molar conductivity of a weak electrolyte decreases with dilution

Molar conductivity of a strong and weak electrolyte increases with dilution

Solution

Question 4

326.6 S cm2 mol-1

38.6 S cm2 mol-1

181.6 S cm2 mol-1

90.8 S cm2 mol-1

Solution

Question 5

at infinite dilution the ionic conductivity of ions is additive.

at infinite dilution the ionic conductivity of all the ions of the electrolyte become equal.

at infinite dilution the concentration of the electrolyte becomes unity.

at infinite dilution the concentration of ions increases.

Solution

Question 6

Resistance

Molar conductivity

Conductivity

Conductance

Solution

Question 7

to aqueous solution of strong electrolytes

applicable to electrolytes dissolved in a solvent of low polarity only.

to electrolytes at temperature above room temperature.

to electrolytic solutions at infinite dilution

Solution

Question 8

73.0%

37.0%

63.0%

137.0%

Solution

Question 9

∧m0 increases steeply on dilution especially near lower concentrations.

Weak electrolytes ionize completely in solution

∧m for weak electrolytes does not vary linearly with dilution.

Weak electrolytes dissociated to a much lesser extent as compared to strong electrolytes and therefore, ∧m0 of weak electrolytes is low. It becomes even low at lower concentration.

Solution

Question 10

Increases

Depends on the enthalpy change of dissolution

Decreases

Depends on the nature of salt

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326.6 S cm² mol^-1

38.6 S cm² mol^-1

181.6 S cm² mol^-1

90.8 S cm² mol^-1

∧m⁰ increases steeply on dilution especially near lower concentrations.

Weak electrolytes dissociated to a much lesser extent as compared to strong electrolytes and therefore, ∧m⁰ of weak electrolytes is low. It becomes even low at lower concentration.