Electrochemistry Test

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Electrochemistry Test - 58

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Weekly Quiz Competition

Question 1
1 / -0

What happens when lead storage battery is discharged?

A
$${SO}_{2}$$ is evolved

B
Lead sulphate is consumed

C
Lead is formed

D
$${H}_{2}{SO}_{4}$$ is consumed

Solution

The electrodes of the cells in a lead storage battery consist of lead grids. Dilute sulfuric acid $$H_2SO_4$$ serves as the electrolyte. When the battery is delivering a current, i.e., discharging, the lead at the anode is oxidized. When the cell is under load, there is an electric field in the electrolyte that causes negative ions ($$SO_4^{2-}$$) to drift toward the anode plate. During the discharge operation, acid is consumed and water is produced.
Question 2
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A process in which a thin film of a metal like gold, silver, etc., is deposited on another metallic article with the help of electricity.

A
Electrorefining

B
Electroplating

C
Electrochemical process

D
Galvanization
Question 3
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Select the correct statement.

A
Faraday represents 96500 coulombs per second.

B
Coulomb represents one ampere for 1/2 second.

C
Coulomb represents 1/2 ampere for 1 second.

D
Faraday represents charge of one mole electron.

Solution

Faraday represents charge of one mole electron since $$1F=1C/mole$$
Question 4
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The electrical conductivity of a solution serves as a means of determining the end point in a chemical reaction, involved in the titration of acids, bases, or precipitation. Which of the following conductometric titration represent the curve of HCl vs $$NaOH$$ :
x-axis $$\Rightarrow$$ Volume of alkali added
y-axis $$\Rightarrow$$ Conductivity

A

B

C

D

Solution

Strong Acid with a Strong Base, example for. $$HCl$$ with $$NaOH$$:
Before $$NaOH$$ is added, a conductance is high because of the presence of highly mobile hydrogen ions. While the base is added, the conductance falls due to the replacement of hydrogen ions through the added cation as $$H^+$$ ions react along with $$OH^ -$$ ions to form undissociated water. That decrease in the conductance continues till the equivalence point. At the equivalence point, a solution holds just $$NaCl$$. After the equivalence point, the conductance increases because of the huge conductivity of $$OH^-$$ ions.
Question 5
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What is the charge on an individual electron, if one $$F$$ is equivalent to $$96,487$$ $${ C }/{ mol }{ e }$$?

A
$$5.76\times { 10 }^{ 28 }{ C }/{ { e }^{ - } }$$

B
$$6.022\times { 10 }^{ 23 }{ C }/{ { e }^{ - } }$$

C
$$1.6\times { 10 }^{ 19 }{ C }/{ { e }^{ - } }$$

D
$$1.6\times { 10 }^{ -19 }{ C }/{ { e }^{ - } }$$

Solution

The Faraday constant, denoted by the symbol F and named after Michael Faraday, is the magnitude of electric charge per mole of electrons.
It has the currently accepted value = $$ 96487 C/mole$$.

The constant F has a simple relation to two other physical constants:
$$F = e. N_A$$
where
$$ e ≈ 1.6021766×10^{−19} C$$
$$N_A = 6.022 \times 10^{23} mol^{-1}$$

$$N_A$$ is the Avogadro constant (the ratio of the number of particles, N, which is unitless, to the amount of substance, n, in units of moles), and e is the elementary charge or the magnitude of the charge of an electron. This relation is true because the amount of charge of a mole of electrons is equal to the amount of charge in one electron multiplied by the number of electrons in a mole.
Question 6
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1 Faraday can be defined as :

A
the magnitude of the charge of 1 mole of electrons

B
the magnitude of the electric dipole

C
a fundamental constant of nature equal to $$\displaystyle 6.63\times { 10 }^{ -34 }\ J \ s/photon$$

D
a constant that accounts for the existence of ions in solution

E
the assignment of charges to individual atoms

Solution

The charge of 1 mole of electrons is called the Faraday Constant, F.
It is calculated by multiplying the charge of one electron by the Avogadro constant.
1 Faraday =$$ 9.648 70 \times 10^{4}$$ coulombs/faraday
Question 7
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When one Faraday current is passed, which of the following would deposit $$1 g$$ atomic weight of the metal?

A
$$NaCl$$

B
$$Ba{Cl}_{2}$$

C
$$Al{Cl}_{3}$$

D
$$CuS{O}_{4}$$

Solution

Gram-atomic weight definition is the mass of one mole of an element equal in grams to the atomic weight

No. of gram equivalents $$=$$ Weight of substance / Equivalent weight

Now, as the valency of $$Na^+$$ in NaCl is $$1$$,

Equivalent weight $$=$$ Molar mass/ valency $$=$$ Molar mass/ 1 $$=$$ molar mass.

1 F will deposit only 1 mole (or one gram equivalent) of Na metal.

No. of equivalent weight deposited $$=$$ molar mass / equivalent weight $$=$$ 1 gm atomic weight.

Hence, option A is correct.
Question 8
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How many Faraday ($$F$$) are required for the reduction of $$1$$ mole of $${ Ni }^{ 2+ }$$ to $$Ni\left( s \right) $$?

A
$$1 F$$

B
$$2 F$$

C
$$96, 487 F$$

D
$$6.022\times { 10 }^{ 23 }F$$

Solution

$$Ni^{2+} + 2e^- \rightarrow Ni$$

1 mole of $$Ni^{2+}$$ requires 2 moles of electrons to be reduced to $$Ni$$.

1 mole of electrons has $$1 F $$ charge, hence 2 moles of electrons have $$2F$$ charge.
Question 9
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What is not Avogadro's number ?

A
The number of atoms in 11.2 L of $$\displaystyle { O }_{ 2 }$$ at STP

B
The number of atoms in 1 mole of $$\displaystyle He$$ at STP

C
The number of electrons in 96,500 coulombs

D
The number of $$\displaystyle { SO }_{ 4 }^{ 2- }$$ ions in 1 L of 0.5 M sulphuric acid

E
None of the above
Question 10
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About an electrolyte cell, which of the following is true?

A
An electric current causes an otherwise non-spontaneous chemical reaction to occur

B
Reduction occurs at the anode

C
A spontaneous electrochemical reaction produces an electric current

D
The electrode to which electrons flow is where oxidation occurs

E
None of the above