Tag: extraction of metals by electrolysis

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

The same amount of electricity was passed through two separate electrolytic cells containing solutions of nickel nitrate $[Ni(NO _{3}) _{2}$] and chromium nitrate $[Cr(NO _{3}) _{3}$] respectively.If 0.3 g of nickel was deposited in the first cell, the amount of chromium deposited is:
(at.wt of Ni=59, at. wt. of Cr=52)

  1. 0.1 g

  2. 0.17 g

  3. 0.3 g

  4. 0.6 g
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

On electrolysing a solution of dilute ${ H } _{ 2 }{ SO } _{ 4 }$ between platinum electrodes, the gas evolved at the anode is 

  1. ${ SO } _{ 2 }$
  2. ${ SO } _{ 3 }$
  3. ${ O } _{ 2 }$
  4. ${ H } _{ 2 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

During the electrolysis of dilute sulfuric acid using platinum electrodes, water is oxidized at the anode rather than sulfate ions, releasing oxygen gas (O2).

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

In the manufacture of $NaOH$ by the electrolysis of $NaCl$ solution, the cathode and anode are separated using a diaphragm because :

  1. it prevents the reaction betweeen ${H _2}$ and $C{l _2}$ formed
  2. it prevents the mixing of $NaOH$ and $NaC{l _2}$
  3. it prevents the reaction betweeen $Na$ and $C{l _2}$ formed
  4. it increases the yield of $NaOH$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice chemistry chemical changes applications of electrolysis electroplating extraction of metals by electrolysis

Charge required for liberating $710 g$ of $Cl _{2}(g)$ by electrolyzing a concentrated solution of $NaCl$ will be:

  1. $1.93$ x $10^{5}$ $C$
  2. $1.93$ x $10^{6}$ $C$
  3. $9.65$ x $10^{6}$ $C$
  4. $9.65$ x $10^{5}$ $C$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The reaction taking place at anode is given by:

$2Cl^- \rightarrow Cl _2+2e^-$
Thus, $2$ moles of $e^-$ are required to liberate $1$ mole of $Cl _2$
Moles of $Cl _2=\dfrac{710}{71}=10$
Hence moles of $e^-$ required $=2\times10=20$
Hence $Q=20F$
$\Rightarrow Q=20\times 96500$
$\Rightarrow Q=1.93\times10^6 C$

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

Which process occurs in the electrolysis of an aqueous solution of nickel chloride at nickel anode?

  1. $Ni\rightarrow Ni^{2+}+2e^{-}$
  2. $Ni^{2+}+2e^{-}\rightarrow Ni$
  3. $2CI^{-}\rightarrow 2CI _{2}+2e^{-}$
  4. $2H^{+}+2e^{-}\rightarrow H _{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

At a nickel anode in an electrolytic cell, the metal itself undergoes oxidation (Ni -> Ni2+ + 2e-) because nickel is an active electrode.

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

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
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Delta G = -nFE. For the reaction 4Al + 3O2 -> 2Al2O3, n = 12 electrons. Delta G = -965 kJ/mol O2. Since 3 moles of O2 are used, total Delta G = 3 * -965 = -2895 kJ. E = -Delta G / nF = 2895000 / (12 * 96500) = 2.5 V.

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

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.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For high-quality electroplating, a low current density is required to ensure a smooth, uniform, and firm deposit. A high current would result in a rough, powdery, or non-adherent deposit.

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

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. $2{ Ag }^{ + }+{ e }^{ \ _ }\longrightarrow Ag$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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


$Ag - e^-\rightarrow Ag^+$.