Tag: electroplating

Questions Related to electroplating

On the basic of information available from the reaction
$ 4AI + 3O _{2} \rightarrow 2AI _{2}O _{3}; \triangle G = -965$ kJ/mol of $O _{2}$
The minimum EMF required to carry out electrolysis of $ AI _{2}O _{3}$ is

  1. 0.833 V

  2. 2.5 V

  3. 5.0 V

  4. 1.67 V


Correct Option: B

By selecting electrolyte as sodium argentocyanide for electroplating of the metal article with silver. Which of the following condition ensures that deposit is smooth, firm and long-lasting?

  1. low direct current should be passing for long time

  2. low indirect current should be passing for long time

  3. low direct current should be passing for short time

  4. low indirect current should be passing for long time.


Correct Option: A

A current of 3.7 A is passed for 6 h between nickel electrodes in 0.50 1 of 2 M solution of $Ni(NO _{3}) _{2}$. The molarity of $Ni^{2+}$ at the end of electrolysis is

  1. 1.172 M

  2. 0.172 M

  3. 0.586 M

  4. 2 M


Correct Option: D

Which of the following reaction taken place at anode during electroplating of metal with silver using sodium argentocyanide as an electrolyte?

  1. $Ag\quad -{ e }^{ \ _ }\longrightarrow { Ag }^{ \ + }$

  2. ${ Ag }^{ + }+{ e }^{ \ _ }\longrightarrow Ag$

  3. $Ag\quad -2{ e }^{ \ _ }\longrightarrow { Ag }^{ \ +}\quad +{ e }^{ \ - }$

  4. $2{ Ag }^{ + }+{ e }^{ \ _ }\longrightarrow Ag$


Correct Option: A
Explanation:

In electroplating with silver, oxidation reaction at anode takes place:


$Ag - e^-\rightarrow Ag^+$.

 Which electrolyte is selected for the electroplating of metal article with silver?

  1. Argentocyanide

  2. Silver nitrate

  3. Silver chloride

  4. Cyanochloride


Correct Option: A

During silver plating of an article using potassium argentocyanide as an electrolyte, the anode material should be :

  1. Cu

  2. Ag

  3. Pt

  4. Fe


Correct Option: B
Explanation:

During silver plating of an article using potassium argentocyanide as an electrolyte,
Cathode - Article to be electroplated.
Anode - Block of silver metal

Which of the following reaction takes place at the cathode during electroplating of metal with silver using sodium argentocyanide as an electrolyte?

  1. ${ Ag }^{ + }+{ e }^{ \ _ }\longrightarrow Ag$

  2. $Ag \longrightarrow { Ag }^{ \ _ } + { e }^{ \ _ }$

  3. $2{ Ag }^{ + }+{ e }^{ \ _ }\longrightarrow Ag$

  4. $Ag^+\longrightarrow { Ag }^{ \ _ } +{ e }^{ \ _ }$


Correct Option: A
Explanation:

In electroplating with silver,
reaction at cathode:
$Ag^+ +e^-\rightarrow Ag$.

During electroplating of an article with nickel, the reduction reaction of the electrolysis occurs at:

  1. cathode

  2. anode

  3. both $A$ and $B$

  4. none of these


Correct Option: A
Explanation:

No matter what, reduction always occurs at cathode. 

In the electroplating of silver, $AgNO _3$ solution is usually used as:

  1. oxidant

  2. reductant

  3. electrode

  4. electrolyte


Correct Option: D
Explanation:

The process of depositing a thin layer of silver electrolytically on the metal surface is called silver plating. The article to be silver-plated is used as cathode while anode consists of pure silver. 


The bath contains a solution of potassium argentocyanide ($AgNO _3$ + excess of KCN). The complex ion is very stable and ionisation is very small at a time with the result slow and uniform deposition of silver takes place. 

$[Ag(CN) _2]^2 \rightleftharpoons Ag^+ + 2CN^-$


Hence, option D is correct.

The metal which is deposited at the cathode during the electrolysis of the solution of silver chloride 

is:  

  1. Ag

  2. H

  3. Cl

  4. Na


Correct Option: A
Explanation:

Reactions:
At cathode:
$Ag^+ +e^-\rightarrow Ag$
At anode:
$2 H _2O \rightarrow O _2 + 4H^+ + 4 e^-$