Tag: electroplating

Questions Related to electroplating

Calculate the mass of Ag deposited at cathode when a current of 2A was passed through a solution of $Ag{ NO } _{ 3 }$ for 15 min.
(Given : Molar mass of $Ag = 108\ g\ { mol }^{ -\ 1 }$ $\ 1F=96500\ C\ { mol }^{ -1 }$).

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

  1. $3.015\ g$

  2. $2.015\ g$

  3. $4.2\ g$

  4. $3.1\ g$

Show answer
Correct Option: B
Explanation:

Given:

Molar Mass of Ag = 108 g/mol

$1F = 96500\ C mol^{−1}$

Reaction at cathode = $Ag + e^-  \rightarrow   Ag(s)$ 

$w = Zlt$

Where, w = Mass deposited at cathode

Z = electrochemical constant

I = current

t = time

Now I = 2amp

$t = 15\ min = 15\times 60 = 900\ seconds$

Z = Eq. wt of substance $/ 96500 = 108/96500$ 

So,

$w = \dfrac{108}{96500} \times 900 \times 2 $

= $2.015g$

The electrochemical equivalent of silver is $0.0011180g$. When an electric current of $0.5$ ampere is passed through an aqueous silver nitrate solution for $200sec$, the amount of silver deposited is:

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

  1. $1.1180g$

  2. $0.11180g$

  3. $5.590g$

  4. $0.5590g$

Show answer
Correct Option: B
Explanation:

According to the data given when $1$ e is passed the amount of silver,

deposited is $0.0011180\,g$
$\therefore (0.5\times 200)c$ is passed
then $(0.0011180\times 100)g$
of silver gets deposited 
$=0.11180\,g$

Brine solution on electrolysis will not give__________.

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

  1. $NaOH$

  2. ${Cl} _{2}$

  3. ${H} _{2}$

  4. ${O} _{2}$

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Correct Option: D

$H _2(g)$ and $O _2(g)$ , can be produced by the electrolysis of water. What total volume (in $L$) of $O _2$ and $H _2$ are produced at $STP$ when a current of $30$ A is passed through a $K _2SO _4\, (aq)$  solution for 193 minutes?

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

  1. 20.16

  2. 40.32

  3. 60.48

  4. 80.64

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Correct Option: D

During the mid ninteenth century, Daguerro-type portraits were very popular. A portrait image of a person was made on silver plated copper by developing the image with ?

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

  1. Silver bromide

  2. Mercury vapour

  3. 'Hypo' (sodium hypochlorite)

  4. An iodine solution

Show answer
Correct Option: B
Explanation:
The latent image was developed to visibility by several minutes of exposure to the forms given off by heated mercury in purpose made developing box.
So development process of Daguerro-type portraits is done with Mercury Vapour.

Silver can be spread as a thin sheet on another metal by electroplating. The film of silver sticks strongly to the metal. Which of the following metals cannot be properly plated with silver?

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

  1. Copper

  2. Iron

  3. Nickel

  4. Brass

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Correct Option: B
Explanation:

Iron cannot be property plated with silver it becomes peel if plated with silver are to peeling of silver it cannot properly plated iron.

In electroplating of copper by silver, the silver acts as an :

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

  1. anode

  2. cathode

  3. electrode

  4. electrolyte

Show answer
Correct Option: A
Explanation:

Silver plating on Steel spoon: A silver rod is made as anode and steel spoon as cathode. Potassiumargentocyanide $(K[Ag(CN) _2])$ is used as electrolyte.
$AgNO _3$ is not used as electrolyte because in that case the silver coating will be non-uniform as the electrolysis takes place rapidly.
In electroplating of copper by silver, silver rod is taken as anode.

Electrolysis of brine produces Na at cathode.

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

  1. True

  2. False

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Correct Option: B
Explanation:

Electrolysis of brine or NaCl produces hydrogen at cathode and chlorine at anode while the electrolyte NaOH sodium hydroxide remains in the solution.

 In the silver plating of copper, $K[Ag(CN) _2]$ is used instead of $AgNO _3$. The reason is:

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

  1. a thin layer of Ag is formed on Cu

  2. more voltage requirement

  3. $Ag^+$ ions are completely removed from solution

  4. less availability of $Ag^+$ ions, as Cu cannot displace Ag from $[Ag(CN) _2]^-$ ion

Show answer
Correct Option: D
Explanation:

Option D is correct 

less avaibality of $Ag+$ions as, $Cu$ cannot displace $Ag$ from $[Ag(CN) _2]$
$Cu$ can replace $Ag$ in $AgNO _3$. But In coordination compound $Ag$ can't be replaced.

In $Ag$ - $CuSO _{4}$ cell, silver electrode will serve as:

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

  1. anode

  2. cathode

  3. both anode and cathode

  4. none of the above

Show answer
Correct Option: B
Explanation:
In $Ag - CuSO _4$ cell, silver electrode will serve as cathode, as reduction occurs here and silver metal is deposited. Copper being high in the reactivity series than silver, undergoes oxidation, and silver ions undergo reduction.