Electrochemistry Test

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Electrochemistry Test - 3

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Question 1
1 / -0.25

According to Faraday ’s Second Law of Electrolysis the amounts of different substances liberated by the same quantity of electricity passing through the electrolytic solution are proportional:

A
To their atomic weight .

B
To their nuclear masses

C
Their chemical equivalent weights

D
To their Atomic number

Solution

The amounts of different substances liberated by the same quantity of electricity passing through the electrolytic solution are proportional to their chemicalequivalent weights.
Question 2
1 / -0.25

Charge on one mole of electrons i.e. one Faraday is approximately:

A
99500 C mol^-1

B
98500 C mol^-1

C
97500 C mol^-1

D
96500 C mol^-1

Solution

Charge on one electron is 1.6 x 10^-19 C.
1 mole of electron 6.023 x 10²³ electrons.
So charge on one mole of electron = 1.6 x 10^-19 C x 6.023 x 10²³ = 96500 C mol^-1
Question 3
1 / -0.25

In the primary batteries,

A
The reaction occurs only once and after use over a period of time battery becomes dead and cannot be reused again.

B
The reaction is reversed periodically and after use over a period of time and so can be reused again.

C
The reaction occurs only once and after use over a period of time battery becomes dead and can be reused again.

D
None of these

Solution

Primary batteries cannot be recharged and reused.
Question 4
1 / -0.25

A secondary cell after use ________ recharged by passing current through it in the ________ so that it can/can ’t be used again.

A
can be, opposite direction

B
cannot be, opposite direction

C
can be, same direction

D
none of these

Solution

Secondary cell can be recharged and reused.
Question 5
1 / -0.25

Fuel cells are _________ that are designed to convert the energy of combustion of fuels like hydrogen, methane, methanol, etc. directly into _________.

A
Galvanic cells, electrical energy

B
Electrolytic cells, electrical energy

C
Galvanic cells, hydraulic energy

D
Galvanic cells, thermal energy
Solution
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) directly into electrical energy through a pair of redox reactions.
Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from metals and their ions or oxides that are commonly already present in the battery, except in flow batteries.
Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied.
Setup of a Fuel cell:
Question 6
1 / -0.25

In corrosion, a metal is _________ of electrons to oxygen and results in the formation of oxides.

A
Reduced by loss

B
Oxidized by loss

C
Oxidized by gain

D
None of these
Solution
In Corrosion, a metal is oxidized by loss of electrons and results in the formation of oxides.
Corrosion is a natural process that converts a refined metal into a more chemically stable form such as oxide, hydroxide, or sulfide.
It is the gradual destruction of materials (usually a metal) by chemical and/or electrochemical reaction with their environment.
Corrosion engineering is the field dedicated to controlling and preventing corrosion.
Question 7
1 / -0.25

One of the simplest methods of preventing corrosion is to prevent the surface of the metallic object to come in contact with atmosphere. This can be done:

A
By covering the surface with oil

B
By covering the surface with salt

C
By covering the surface with citric acid

D
By covering the surface with paint or by some chemicals
Solution
The best way to prevent corrosion is to prevent the surface of the metallic objects to come in contact with the atmosphere.
The rusting of iron can be prevented by painting, oiling, greasing or varnishing its surface.
Galvanization is another method of protecting iron from rusting by coating iron with a thin layer of zinc.
Corrosion of iron is prevented by coating iron with non-xcorrosive substance like carbon. This process is termed as alloying .
Question 8
1 / -0.25

An electrochemical method is to provide a sacrificial electrode of another metal (like Mg, Zn, etc.) which corrodes itself but saves the object. A typical example is

A
Painted iron

B
Galvanized iron

C
Black oxidised iron

D
Grounded iron

Solution

Galvanization is a process in which iron is coated with reactive metal like Zn which get corroded hence preventing iron from corrosion.
Electro-Galvanization:
Question 9
1 / -0.25

Correct arrangement of Al, Cu, Fe, Mg and Zn in the order in which they displace each other from the solution of their salts is

A
Mg, Al, Zn, Fe, Cu

B
Mg, Al, Zn, Cu, Fe

C
Mg, Al, Cu, Fe, Zn

D
Cu, Al, Zn, Fe, Mg

Solution

A more reactive metal displaces a less reactive metal from the salt solution (refer to reactivity series).
The order in which metals displace each other from the solution of their salts can be given with the help of their standard electrode potential . Since magnesium has the least standard electrode potential so it is the most strong reducing agent.
So the required order we get is: Mg >Al >Zn >Fe >Cu
Reactivity Series:
Question 10
1 / -0.25

The standard emf of galvanic cell involving 3 moles of electrons in its redox reaction is 0.59 V. The equilibrium constant for the reaction of the cell is

A
10²⁵

B
10²⁰

C
10¹⁵

D
10³⁰

Solution

The standard emf of a galvanic cell involving 3 moles of electrons in its redox reaction is 0.59V.
E º_cell = 0.59V
n=3
The equilibrium constant for the reaction of the cell is given by the expression: ln K = RT nFE º_cell
ln K = 8.314 ×298 ×3 ×96500 ×0.59 = 68.9
K ≈10³⁰
The equilibrium constant for the reaction of the cell is 10³⁰ .

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Electrochemistry Test - 3

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Question 1

To their atomic weight .

To their nuclear masses

Their chemical equivalent weights

To their Atomic number

Solution

Question 2

99500 C mol-1

98500 C mol-1

97500 C mol-1

96500 C mol-1

Solution

Question 3

The reaction occurs only once and after use over a period of time battery becomes dead and cannot be reused again.

The reaction is reversed periodically and after use over a period of time and so can be reused again.

The reaction occurs only once and after use over a period of time battery becomes dead and can be reused again.

None of these

Solution

Question 4

can be, opposite direction

cannot be, opposite direction

can be, same direction

none of these

Solution

Question 5

Galvanic cells, electrical energy

Electrolytic cells, electrical energy

Galvanic cells, hydraulic energy

Galvanic cells, thermal energy

Solution

Question 6

Reduced by loss

Oxidized by loss

Oxidized by gain

None of these

Solution

Question 7

By covering the surface with oil

By covering the surface with salt

By covering the surface with citric acid

By covering the surface with paint or by some chemicals

Solution

Question 8

Painted iron

Galvanized iron

Black oxidised iron

Grounded iron

Solution

Question 9

Mg, Al, Zn, Fe, Cu

Mg, Al, Zn, Cu, Fe

Mg, Al, Cu, Fe, Zn

Cu, Al, Zn, Fe, Mg

Solution

Question 10

1025

1020

1015

1030

Solution

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99500 C mol^-1

98500 C mol^-1

97500 C mol^-1

96500 C mol^-1

10²⁵

10²⁰

10¹⁵

10³⁰