Electrochemistry Test

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Electrochemistry Test - 20

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Weekly Quiz Competition

Question 1
1 / -0

The electrochemical cell stops working after some time because:

A
electrode potentials of both electrodes becomes zero

B
electrode potentials of both electrodes becomes equal

C
temperature of the cell increases

D
the reaction starts proceeding in opposite direction

Solution

$$\bf{Hint-}$$ An electrochemical cell is a device that produces an electric current from the energy released by a spontaneous redox reaction.

$$\bf{Explanation-}$$

Electrochemical cells stop working after some time because,
When one compound in the anode of the electrochemical cell is oxidised, those electrons serve to reduce the compound on the cathode side.
When the material at the anode does not have electrons to lose, hence the reaction stops and the cell stops working.

$$\bf{Final\ answer-}$$ Option $$B$$
Question 2
1 / -0

Which of the following is not true?

A
The electrode which pushes electrons into external circuit is known as anode

B
The electrode which pulls electrons out of external circuit is known as cathode

C
Weak electrolytes conduct relatively small quantity of electricity than strong electrolytes

D
Effect of dilution on conductance of strong electrolyte can be explained by Arrhenius theory.

Solution

Arrhenius theory only explains the effect of dilution on conductance of weak electrolysis
The effect on strong electrolytes is explained by thicket onsagar equation
Question 3
1 / -0

A half cell reaction is one which:

A
involves only half a mole of electrolyte

B
goes only half way to completion

C
takes place at one electrode

D
consumes half a unit of electricity

Solution

In an electrochemical cell, a redox reaction occurs. Oxidation occurs at one electrode and reduction occurs at another electrode. The reaction occuring at each electrode is known as half cell reaction.
Hence, option C is the correct one.
Question 4
1 / -0

Corrosion is a/an:

A
physical change

B
neutralisation reaction

C
electrochemical change

D
none of the above

Solution

Hint: Corrosion is the oxidation of metal by moist air, often unwanted.

Corrosion is an electrochemical change. A highly reactive metal (easily oxidisable) is oxidised in the anodic reaction $$M^{x+} + xe^- \rightarrow M$$. Highly reactive metals are more easily corroded unless they form a protective oxide layer around them on oxidation which prevents further oxidation. Noble metals like $$Pt$$ are not easily corroded.

Final answer: electrochemical change.
Hence, option $$C$$ is correct.
Question 5
1 / -0

In an electrolytic cell, the current flows from:

A
cathode to anode in outer circuit

B
anode to cathode outside the cell

C
cathode to anode inside the cell

D
current does not flow

Solution

In the electrolytic cell, the current flows from the cathode to anode in the outer circuit.

In the electrolytic cell, electrical energy is converted to chemical energy.

Option A is correct.
Question 6
1 / -0

The magnitude of charge present on one azide ion in coulombs is:

A
$$96500$$

B
$$4.8 \times 10^{19}$$

C
$$4.8 \times 10^{-19}$$

D
$$1.6 \times 10^{-19}$$

Solution

The charge of one electron is $$-1.602 \times { 10 }^{ -19 }\ \text C $$.

The azide ion $$ { N }_{ 3 }^{ - } $$ has unit negative charge which is equal to the charge on one electron.

Hence, the magnitude of charge on one azide ion is equal to $$ 1.602 \times { 10 }^{ -19 }\ \text C $$.

Option D is correct.
Question 7
1 / -0

Number of Faradays involved in the net reaction of Lead accumulator is __________.

A
1

B
0.5

C
2

D
cannot be predicted

Solution

For lead accumulator battery, the oxidation reaction at anode requires two moles of electrons. Similarly, the reduction reaction at cathode requires two moles of electrons. Hence, the number of Faradays involved in the net reaction of Lead accumulator is 2.
Note: 1 Faraday is equal to the amount of charge on 1 mole of electrons.
Question 8
1 / -0

In corrosion of iron,

A
electrons flow from anode to cathode through the metal, while ions flow through the water droplets

B
an electrochemical (galvanic) cell is formed in which $$Fe$$ acts as anode and $$O_{2}$$ is reduced at cathode

C
dissolved $$O_{2}$$ oxidizes $$Fe^{2+}$$ to $$Fe^{3+}$$ before it is deposited as rust $$(Fe_{2}O_{3}.xH_{2}O)$$

D
All of the above takes place

Solution

The corrosion of iron is an electrochemical process. The anode region and cathode region are present in iron. $$Iron(II)$$ is oxidized to $$Iron(III)$$ by oxygen and is then converted to rust. At the cathode, oxygen is reduced. The electron flow is from anode to cathode through metal.
This is accompanied by the flow of ions through water droplets.
Question 9
1 / -0

In which of the following the corrosion of iron will be most rapid?

A
In pure water

B
In pure oxygen

C
In air and moisture

D
In air and saline water

Solution

The corrosion of iron indicates a chemical change in the metal. Rust (hydrous oxide) is an example of this change that results when the iron is exposed to water or damp air. A thin film of oxide forms on the iron; this actually protects the metal from further corrosion by slowing the rate of oxidation.

Where salt is present, electrochemical corrosion occurs, and the protective oxide film does not form, thus the corrosion (buildup of rust) continues unchecked. Hence corrosion is faster in saline water.

Hence, option D is correct.
Question 10
1 / -0

The factors that promote electro chemical corrosion are _____________.

A
the nature of the impurity metal with which the metal under consideration is associated.

B
the concentration of $$O_{2}$$ in contact with the surface of the metal.

C
highly conducting solutions.

D
all the above.

Solution

Pure metals are resistive to corrosion. If there are impurities in a metal, a local galvanic cell is created with the metal as an anode and the impurity as a cathode. The result is the corrosion of the metal. And in the presence of a high concentration of oxygen, corrosion will be faster. Also when the conductivity of solutions is higher, the corrosion will be faster.
Hence, option D is correct.

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Electrochemistry Test - 20

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Question 1

electrode potentials of both electrodes becomes zero

electrode potentials of both electrodes becomes equal

temperature of the cell increases

the reaction starts proceeding in opposite direction

Solution

Question 2

The electrode which pushes electrons into external circuit is known as anode

The electrode which pulls electrons out of external circuit is known as cathode

Weak electrolytes conduct relatively small quantity of electricity than strong electrolytes

Effect of dilution on conductance of strong electrolyte can be explained by Arrhenius theory.

Solution

Question 3

involves only half a mole of electrolyte

goes only half way to completion

takes place at one electrode

consumes half a unit of electricity

Solution

Question 4

physical change

neutralisation reaction

electrochemical change

none of the above

Solution

Question 5

cathode to anode in outer circuit

anode to cathode outside the cell

cathode to anode inside the cell

current does not flow

Solution

Question 6

$$96500$$

$$4.8 \times 10^{19}$$

$$4.8 \times 10^{-19}$$

$$1.6 \times 10^{-19}$$

Solution

Question 7

1

0.5

2

cannot be predicted

Solution

Question 8

electrons flow from anode to cathode through the metal, while ions flow through the water droplets

an electrochemical (galvanic) cell is formed in which $$Fe$$ acts as anode and $$O_{2}$$ is reduced at cathode

dissolved $$O_{2}$$ oxidizes $$Fe^{2+}$$ to $$Fe^{3+}$$ before it is deposited as rust $$(Fe_{2}O_{3}.xH_{2}O)$$

All of the above takes place

Solution

Question 9

In pure water

In pure oxygen

In air and moisture

In air and saline water

Solution

Question 10

the nature of the impurity metal with which the metal under consideration is associated.

the concentration of $$O_{2}$$ in contact with the surface of the metal.

highly conducting solutions.

all the above.

Solution

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