Electrochemistry Test

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Electrochemistry Test - 8

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Weekly Quiz Competition

Question 1
1 / -0

Resistance of 0.2 M solution of an electrolyte is 50Ω. The specific conductance of the solution is 1.3s m^-1. If resistance of the 0.4 M solution of the same electrolyte is 260Ω, its molar conductivity is

A
625 × 10⁻⁴S m²mol⁻¹

B
62.5 S m²mol⁻¹

C
6.25 × 10⁻⁴S m²mol⁻¹

D
6250 S m²mol⁻¹

Solution

κ = G × cell constant and G= 1/R. For 0.2M solution, R = 50 ohms, k= 1.3Sm^-1,cell constant l/A = 50 × 1.3 = 65m^-1
Λm = k/c for 0.4M solution , molar conductivity = ? , R = 260ohms, cell constant = 65m^-1 so K = 65/260 = 0.25 Sm^-1
molar conductivity = K × 1000/M = 0.25/0.4 × 1000 = 6.25 × 10^-4Sm²/mol
Question 2
1 / -0

An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to

A
decrease in both i.e. number of ions and mobility of ions

B
decrease in ionic mobility

C
increase in concentration of electrolyte

D
increase in ionic mobility and number of ions

Solution

Equivalent conductance increases on dilution for a strong electrolyte as interionic attraction also decreases along with dilution. So ionic mobility increases which in turn increases the equivalent conductance.
Question 3
1 / -0

Which of the following electrolytic solutions has the least specific conductance?

A
2 N

B
0.2 N

C
0.02 N

D
0.002 N

Solution

Specific conductance or conductivity decreases with decrease in concentration of the electrolytic solution as the number of ions per unit volume that carry the current in a solution decrease on dilution.
Question 4
1 / -0

The highest electrical conductivity of the following aqueous solutions is of

A
0.1 M acetic acid

B
0.1 M difluoroacetic acid

C
0.1 M chloroacetic acid

D
0.1 M fluoroacetic acid

Solution

Acidity increases on attaching electron withdrawing group because of stability of conjugate base. Conduction of electric charge depends on the ions. so higher the number of ions higher is electrical conductivity. As fluoro group causes negative inductive effect increasing ionisation, it gives stable ions in solution. also in difluoroacetic acid, the presence of 2 fluorine atom increases the negative inductive effect.
Question 5
1 / -0

Saturated solution of KNO₃ is used to make 'salt bridge' because

A
velocity of NO₃^- is greater than that of K⁺

B
velocity of both K⁺ and NO₃^- are nearly the same.

C
KNO₃ is highly soluble in water

D
velocity of K⁺ is greater than that of NO₃^-

Solution

Saturated solution of KNO₃ is used in salt bridge because of same mobility of K⁺ and NO⁻₃. if the velocities would not have been the same then the ions would not have been able to neutralise the charge equally in both half cells. consequently, an opposing force would be developed that restricts the flow of current.
Question 6
1 / -0

Li occupies higher position in the electrochemical series of metals as compared to Cu since

A
the standard reduction potential of Li⁺/Li is lower than that of Cu²⁺/Cu

B
the standard oxidation potential of Li⁺/Li is lower than that of Cu²⁺/Cu

C
Li is smaller in size as compared to Cu

D
the standard reduction potential of Cu²⁺/Cu is lower than that of Li⁺/Li

Solution

Li is alkali metal E^o Li⁺/Li = -3.045V.

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Electrochemistry Test - 8

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Electrochemistry Test - 8

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Question 1

625 × 10−4 S m2 mol−1

62.5 S m2 mol−1

6.25 × 10−4 S m2 mol−1

6250 S m2 mol−1

Solution

Question 2

decrease in both i.e. number of ions and mobility of ions

decrease in ionic mobility

increase in concentration of electrolyte

increase in ionic mobility and number of ions

Solution

Question 3

2 N

0.2 N

0.02 N

0.002 N

Solution

Question 4

0.1 M acetic acid

0.1 M difluoroacetic acid

0.1 M chloroacetic acid

0.1 M fluoroacetic acid

Solution

Question 5

velocity of NO3- is greater than that of K+

velocity of both K+ and NO3 - are nearly the same.

KNO3 is highly soluble in water

velocity of K+ is greater than that of NO3-

Solution

Question 6

the standard reduction potential of Li+/Li is lower than that of Cu2+/Cu

the standard oxidation potential of Li+/Li is lower than that of Cu2+/Cu

Li is smaller in size as compared to Cu

the standard reduction potential of Cu2+/Cu is lower than that of Li+/Li

Solution

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625 × 10⁻⁴S m²mol⁻¹

62.5 S m²mol⁻¹

6.25 × 10⁻⁴S m²mol⁻¹

6250 S m²mol⁻¹

velocity of NO₃^- is greater than that of K⁺

velocity of both K⁺ and NO₃^- are nearly the same.

KNO₃ is highly soluble in water

velocity of K⁺ is greater than that of NO₃^-

the standard reduction potential of Li⁺/Li is lower than that of Cu²⁺/Cu

the standard oxidation potential of Li⁺/Li is lower than that of Cu²⁺/Cu

the standard reduction potential of Cu²⁺/Cu is lower than that of Li⁺/Li