Tag: chemical changes

Questions Related to chemical changes

Why is electroplating done?

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

  1. to increase attractiveness

  2. to purify an impure metal

  3. to prevent rusting

  4. all of the above

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Correct Option: A,C

Electroplating is a process of deposition of ________ metal on the surface of _________ metal.

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

  1. inferior, superior

  2. superior, superior

  3. inferior, inferior

  4. superior, inferior

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Correct Option: D
Explanation:

Electroplating is a process of deposition of superior metal on the surface of inferior metal.

Anode is the _________ block and cathode is the _________ block in electrorefining of metal.

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

  1. impure, pure

  2. pure, pure

  3. impure, impure

  4. pure, impure

Show answer
Correct Option: A
Explanation:

Anode is the impure block and cathode is the pure block in electro-refining of metal.

Electroplating is ________________ of metals and electro-refining is ___________ of metals.

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

  1. depositing, refining

  2. plating, extracting

  3. refining, depositing

  4. none of the above

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Correct Option: A
Explanation:

Electroplating is $depositing$ of metals and electro-refining is $refining$ of metals.

The main applications of electrolysis are:

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

  1. electroplating

  2. electrorefining

  3. extraction of metals

  4. All of the above

Show answer
Correct Option: D
Explanation:

The main application of electrolysis are:


Electroplating: Electroplating is a process of depositing a layer of any desired metal on another material by means of electricity.

Electrorefining: Electrorefining refers to the process of using electrolysis to increase the purity of a metal extracted from its ore.

Extraction of metals: Extractions are a way to separate the desired substance when it is mixed with others. 

Hence, option D is correct.

Which one of the following is not a main application of electrolysis?

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

  1. Electrorefining

  2. Electrode cleaning

  3. Extraction of metals

  4. Electroplating

Show answer
Correct Option: B
Explanation:

The main application of electrolysis are:

  • Electrorefining
  • Electroplating
  • Extraction of metals

When an external current is used to induce a non-spontaneous redox reaction, the process is called ________.

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

  1. neutralization

  2. hydrolysis

  3. electrolysis

  4. esterification

  5. galvanization

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Correct Option: C
In an electroplating experiment with a $Cu^{2+}$ solution, $10.0$ amp is applied for $965\ sec$. How many moles of $Cu$ will be plated?
chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

  1. $0.05\ \text{moles}$

  2. $0.1\ \text{moles}$

  3. $0.001\ \text{moles}$

  4. $0.005\ \text{moles}$

Show answer
Correct Option: A
Explanation:
$w = {Z\times I\times t}$

$w = \dfrac{E\times I\times t}{96500}$

$w = \dfrac{Molecular\ weight \times I\times t}{2\times 96500}$                                                 [$\therefore E= M/n$]

n=2

$n = \dfrac{w}{M} = \dfrac{I\times t}{2\times 96500}$

$ n=$ $\dfrac{10\times 965}{2\times 96500} = 0.05\ moles$

Hence, option A is correct.

In the electrolysis of $CuCl _{2}$ solution, the mass of cathode increased by $6.4\ g$. What occurred at copper anode?

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

  1. $0.224$ litre of $Cl _{2}$ was liberated

  2. $1.12$ litre of oxygen was liberated

  3. $0.05\ mole\ Cu^{2+}$ passed into the solution

  4. $0.1\ mole\ Cu^{2+}$ passed into the solution

Show answer
Correct Option: D
Explanation:

In the electrolysis process,

reduction takes place at cathode and oxidation takes place at anode
so, if we increase the mass on cathode then same number of moles get oxidised at anode and go into the solution,
so, moles of Cu passed into the solution = $\dfrac{6.4}{63.5} = 0.1 mole$

Which is correct about silver plating?

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

  1. Anode - pure $Ag$

  2. Cathode - object to be electroplated

  3. Electrolyte - $Na[Ag(CN) _{2}]$

  4. All of the above

Show answer
Correct Option: D
Explanation:
In silver plating, the object to be plated (e.g., a spoon) is made from the cathode of an electrolytic cell. 

The anode is a bar of silver metal, and the electrolyte (the liquid in between the electrodes) is a solution of silver cyanide, $AgCN$, in water.

When a direct current is passed through the cell, positive silver ions ($Ag^+$) from the silver cyanide migrate to the negative anode (the spoon), where they are neutralized by electrons and stick to the spoon as silver metal.

Hence, option D is correct.