Tag: applications of electrolysis

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

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

  1. tin plating

  2. zinc plating

  3. copper plating

  4. nickel plating
Reveal answer Fill a bubble to check yourself
B Correct answer
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. 

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

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

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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: $2Al _2O _3\longrightarrow 4Al+3O _2$

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

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]

  1. $2X$
  2. $4X$
  3. $16X$
  4. $32X$
Reveal answer Fill a bubble to check yourself
A Correct answer
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 $A$.
Multiple choice chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

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

  1. $4.2C$
  2. $2.6\times 10^{-3}F$
  3. $126C$
  4. $36C$
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $\displaystyle = \dfrac {252 \ C}{96500 \ C/F}=2.6 \times 10^{-3} \ F$

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

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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?

  1. $KCl$
  2. ${ CuCl} _{ 2 }$
  3. ${ Cu(NO } _{ 3 }{ ) } _{ 2 }$
  4. ${ CuSO } _{ 4 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.
Multiple choice chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

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

  1. $0.4065 g$
  2. $65.04 g$
  3. $40.65 g$
  4. $4.065 g$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

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


                                $=4.065 g.$