Electrochemistry Test

Result

Electrochemistry Test - 12

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Weekly Quiz Competition

Question 1
1 / -0

In a lead storage cell, the EMF

A
increases with increase in the percentage of H₂SO₄

B
decreases with increase in the percentage of H₂SO₄

C
does not change with increase in the percentage of H₂SO₄

D
is not affected by the change in temperature of the cell

Solution

H₂SO₄ is the electrolyte used in the lead storage battery, and the density (hence, the mass percentage) of the electrolyte decreases as the cell is being discharged.
Therefore, as the cell is being discharged, the mass percentage as well as the EMF decrease and vice-versa.
Question 2
1 / -0

Which of the following statements are incorrect?

(A) Dilute sulphuric acid, on electrolysis, liberates oxygen at anode.
(B) The electrical conductivity of acetic acid solution increases when sodium hydroxide solution is added.
(C) Molten sodium hydride liberates O₂ at anode during electrolysis.
(D) During the electrolytic refining of metal, the impure metal is taken as anode.

A
Only (A) and (B)

B
Only (B) and (C)

C
Only (A) and (C)

D
Only (C) and (D)

Solution

During electrolysis, H₂SO₄ liberates oxygen at anode. Hence, the statement (A) is correct.

The electrical conductivity starts decreasing during the addition of sodium hydroxide because OH^- ions neutralise the H⁺ ions of acetic acid and the H₂O formed is a poor electrolyte. Moreover, the sodium acetate formed suppresses the ionisation of acetic acid due to the common ion effect. Hence, the statement (B) is incorrect.

On electrolysis of metal hydrides of s-block elements, the H^- ions move towards anode and are liberated as H₂.

Hence, the statement (C) is incorrect.
Question 3
1 / -0

In the sacrificial protection of iron, three metals Mg, Zn and Al can be used. Choose the one which is the most effective for the purpose. (Mg²⁺/Mg = -2.37 V, Al³⁺/Al = -1.66 V, Zn²⁺/Zn = -0.76 V, Fe²⁺/Fe = -0.44 V)

A
Zn

B
Al

C
Mg

D
Can't determined

Solution

The metal with a lower value of reduction potential is the most effective for the sacrificial protection of the metal.
In this case, Mg has the lowest reduction potential and will be the most effective in protecting the iron object.