Tag: chemical changes

Questions Related to chemical changes

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

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

  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 $NaOH$

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Correct Option: B

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

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

  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 $10^{5}$ $C$

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Correct Option: B
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 $Q=20F$
$\Rightarrow Q=20\times 96500$
$\Rightarrow Q=1.93\times10^6 C$

The correct relation is

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

  1. $\triangle G = -RT\ ln\ K/Q$

  2. $\triangle G = -RT\ ln\ K$

  3. $\triangle G = -RT\ ln\ Q/K$

  4. $\triangle G = +RT\ ln\ Q$

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Correct Option: B
Explanation:

$\triangle G = \triangle G^{\circ} + RT\ ln Q$
$\triangle G = -RT\ ln \dfrac {K}{Q}$.

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

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

  1. $Ni\rightarrow Ni^{2+}+2e^{-}$

  2. $Ni^{2+}+2e^{-}\rightarrow Ni$

  3. $2CI^{-}\rightarrow 2CI _{2}+2e^{-}$

  4. $2H^{+}+2e^{-}\rightarrow H _{2}$

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Correct Option: A

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

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

  1. 0.833 V

  2. 2.5 V

  3. 5.0 V

  4. 1.67 V

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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?

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

  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.

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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

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

  1. 1.172 M

  2. 0.172 M

  3. 0.586 M

  4. 2 M

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Correct Option: D

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

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

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

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

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

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

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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?

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

  1. Argentocyanide

  2. Silver nitrate

  3. Silver chloride

  4. Cyanochloride

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Correct Option: A

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

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

  1. Cu

  2. Ag

  3. Pt

  4. Fe

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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