Tag: applications of electrolysis

Questions Related to applications of electrolysis

The most durable metal plating on iron to protect against corrosion is:

chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

  1. tin plating

  2. zinc plating

  3. copper plating

  4. nickel plating

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Correct Option: B
Explanation:

Metal plating protects the iron against corrosion by forming a sacrificial layer. This metal layer itself gets oxidize instead of iron and thus protects the iron itself. 


For a metal to be used as plating, its oxidation should be preferred over iron and thus should have lower reduction potential than iron. 

Among the given options, zinc has a lower reduction potential than iron and thus can be used for plating. The process is called galvanization.

Hence, option B is correct. 

Extracting metals in the pure form from its compound is known as:

chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

  1. electrorefining

  2. electrochemicals

  3. extraction of metals

  4. electroplating

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Correct Option: C
Explanation:

Extracting metals in the pure form from its compound is known as extraction of metals.

Electroplating is:

chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

  1. the deposition of superior metal on the surface of inferior metal

  2. the deposition of inferior metal on the surface of inferior metal

  3. both A and B

  4. none of the above

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Correct Option: A
Explanation:

The deposition of superior metal on the surface of inferior metal is known as electroplating.

In the electrolysis of molten $Al _2O _3$ with inert electrodes:

chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

  1. Al is oxidized at anode to $Al^{3+}$

  2. $O _2$ gas is produced at anode

  3. $O^{2-}$ is reduced at cathode

  4. $O$ is oxidized at anode

Show answer
Correct Option: B
Explanation:

The electrodes are inert so that they do not involve the electrode reactions but transfer electrons through them. Since the silvery metal i.e. $Al$ is produced at cathode.

At cathode: $Al^{3+}+3e^- \longrightarrow Al$
At anode, $O _2$ bubbles off.
At anode; $2O^{2-}\longrightarrow O _2+4e^-$
The cell reaction: $2Al _2O _3\longrightarrow 4Al+3O _2$

Cost of electricity for the production of $X$ litres of $H _2$ at $NTP$ at the cathode is Rs $X$, then cost of electricity for the production $X$ litres of $O _2$ gas at $NTP$ at the anode will be:


[Assume $1$ mole of electrons as one unit of electricity]

chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

  1. $2X$

  2. $4X$

  3. $16X$

  4. $32X$

Show answer
Correct Option: A
Explanation:

Electrolysis of water gives:


${ H } _{ 2 }O\rightarrow { H } _{ 2 }+\tfrac { 1 }{ 2 } { O } _{ 2 }$


On electrolysis of water, hydrogen, and oxygen formed in the ratio $2:1$.
Since $X$ litres of ${ H } _{ 2 }$ is formed. Amount of ${ O } _{ 2 }$ formed will be $\tfrac { X }{ 2 } $. Since cost of production of electricity from $\tfrac { X }{ 2 } $ litres of ${ O } _2$ = Rs $X$

So, cost of production of electricity from $X$ litres of ${ O } _2$ = Rs $2X$.

So, the correct answer is option $A$.

A solution of $CuSO _4$ is electrolysed for $7$ minutes with a current of $0.6A$. The amount of electricity passed is equal to:

chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

  1. $4.2C$

  2. $2.6\times 10^{-3}F$

  3. $126C$

  4. $36C$

Show answer
Correct Option: B
Explanation:

Quantity of electricity passed $\displaystyle Q(C) = I(A) \times t(s)$
$\displaystyle Q(C)=0.6 \ A \times 7 \ min \times 60 \ s/min$
$\displaystyle Q(C)=252 \ C$
Number of faraday passed $\displaystyle = \dfrac {252 \ C}{96500 \ C/F}=2.6 \times 10^{-3} \ F$

State True or False.
Electrotyping is an application of electrolysis.

chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

  1. True

  2. False

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Correct Option: A
Explanation:

Electrotyping is a chemical method for forming metal parts that exactly reproduce a model.
Electrotyping is related to electroplating, which permanently adds a thin metallic overlayer to a metallic object instead of creating a freestanding metal part. So it is basically an application of electrolysis.

In the electroplating of iron by nickel, nickel sulphate solution is taken as electrolyte. What is the acid that is added to the electrolyte during the process?

chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

  1. $HCl$

  2. $HCN$

  3. $HNO _3$

  4. $H _2SO _4$

Show answer
Correct Option: D
Explanation:

Sulphuric acid is used for pH adjustment during electroplating of nickel.

During electrolysis of an aqueous solution of a salt, pH in the space near one of the electrodes is increased, which of the following salt solution was electrolysed?

chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

  1. $KCl$

  2. ${ CuCl} _{ 2 }$

  3. ${ Cu(NO } _{ 3 }{ ) } _{ 2 }$

  4. ${ CuSO } _{ 4 }$

Show answer
Correct Option: A
Explanation:
As the cation $\left( {K}^{+} \right)$ in $KCl$ has lower electrode potential than $H$, hydrogen is liberated at cathode.

There is an accumulation of ${H}^{+}$ at one electrode, resulting in an increase in pH.

Hence, option A is correct.

A 5-ampere current is passed through a solution of zinc sulphate for $40 $ minutes. The amount of zinc deposited at the cathode is:

chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

  1. $0.4065 g$

  2. $65.04 g$

  3. $40.65 g$

  4. $4.065 g$

Show answer
Correct Option: D
Explanation:

$\because$ $W=z.i.t$=$\cfrac{E}{F}\times{i}.{t}$$=\left(\cfrac{65.38\times5\times40\times60}{2\times96500}\right)g$.


                                $=4.065 g.$