Tag: electrolytic cells and electrolysis

Questions Related to electrolytic cells and electrolysis

State True or False.
Electrolysis of H$ _2$O gives H$ _2$ at the anode.

chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

  1. True

  2. False

Show answer
Correct Option: B
Explanation:
The given statement is false.
The electrolysis of $H _2O$ is explained below:
Cathode (reduction):
$2 H _2O(l) + 2e^- \rightarrow  H _2(g) + 2 OH^-(aq)$
Anode (oxidation):
$ 4 OH^-(aq) \rightarrow O _2(g) + 2 H _2O(l) + 4 e^-$
Thus the electrolysis of $H _2O$ gives $H _2$ at the cathode.
Electrolysis of CaH$ _2$ gives $H _2$ at anode.
chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

The above statement is true.
Electrolysis of $CaH _2$,
At anode,
$2H^-\rightarrow H _2+2e$
at cathode
$Ca^{2+} +2e \rightarrow Ca$

State True or False.
Electrolysis of molten $KCl$ gives Cl$ _2$ at cathode.

chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Electrolysis of molten KCl,
At anode,
$2Cl^-\rightarrow Cl _2+2e$
at cathode
$K^++e\rightarrow K$

Thus the above statement is true.

State True or False.
The ratio of gases liberated at cathode and anode during electrolysis of CH$ _3$COONa(aq) is 1 : 3.

chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

The given statement is True.
 The ratio of gases liberated at cathode and anode during electrolysis of $\displaystyle CH _3COONa$ (aq) is $\displaystyle 1:3$
$\displaystyle 2CH _3COONa \rightarrow CH _3-CH _3 \uparrow + 2CO _2  \uparrow+2NaOH+H _2 \uparrow$
hydrogen gas is liberated at cathode and ethane and carbon dioxide gases are liberated at anode.

Assertion: Dilute H$ _2$SO$ _4$ on electrolysis liberates O$ _2$ at the anode.
Reason: Hydroxide ions have lower discharge potential than sulphate ions.

chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

  1. Both Assertion and Reason are true and Reason is the correct explanation of Assertion

  2. Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

  3. Assertion is true but Reason is false

  4. Assertion is false but Reason is true

  5. Both Assertion and Reason are false

Show answer
Correct Option: A
Explanation:

Dilute H$ _2$SO$ _4$ on electrolysis liberates O$ _2$ at the anode. This is due to lower discharge potential of hydroxide ions than sulphate ions.
$4OH^- \rightarrow 2H _2O + O _2 \uparrow + 4e^-$

In the electrolysis of $Na _{2}SO _{4}$ solution using inert electrode

a) the anodic reaction is

$2H _{2}O\rightarrow O _{2}(g)+4e^{-}+4H^{+}$

b)$H _{2}(g)$ and $O _{2}(g)$ is produced in a molar ratio of 2:1

c) 23 grams of sodium is produced at the cathode

d) the cathode reaction is $Na^{+}+e^{-}\rightarrow Na$

chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

  1. a and b are correct

  2. c,d are correct

  3. only c is correct

  4. all are correct

Show answer
Correct Option: A
Explanation:

The discharge potential of $ { H }^{ + } $ ions is lower than $ { Na }^{ + } $ ions. Hence $ { H }^{ + } $ ions will be liberated at cathode in preference to $ { Na }^{ + } $ ions.
The discharge potential of $ { OH }^{ - } $ ions is lower than $ { SO } _{ 4 }^{ 2- } $ ions. Hence $ { OH }^{ - } $ ions will be liberated at anode (in the form of $ { O } _{ 2 } $ molecule) in preference to $ { SO } _{ 4 }^{ 2- } $ ions. This is the electrolysis of water. Hence $ { H } _{ 2 } $ and $ { O } _{ 2 } $ are produced in the molar ratio of 2:1 which is same as that present in water molecule.

Aqueous solution of nickel sulphate contains $Ni^{2+}$ and ${SO _{4}}^{2-}$ ions. What will be the product at the nickel anode?
chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

  1. $Ni^{2+}$

  2. ${SO _{4}}^{2-}$

  3. $Ni$

  4. $H _2SO _4$

Show answer
Correct Option: A

Which element is evolved at the cathode during the electrolysis of the solution of the hydrogen chloride?

chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

  1. $Cl _2$

  2. $H _2$

  3. $O _2$

  4. $Zn$

Show answer
Correct Option: B
Explanation:

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

Aqueous solution of nickel sulphate contains $Ni^{2+}$ and ${SO _{4}}^{2-}$ ions. Which ion moves towards the cathode?

chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

  1. $Ni^{2+}$

  2. ${SO _{4}}^{2-}$

  3. both A and B

  4. none of these

Show answer
Correct Option: A
Explanation:
 Reaction at cathode (Reduction)  Reaction at Anode (Oxidation)
 Ions at cathode : $Ni^{2+} , H^+$ Preferential discharge of $Ni^{2+}$ ions takes place. $Ni^{2+} (aq) + 2e^- \rightarrow Ni^0(s)$Nickel metal deposits on the article. i.e. nail.  Ions at anode : $SO _4^{2-} , OH^-$$Ni^0 (s) - 2e^- \rightarrow Ni^{2+} (aq)$$Ni^{2+}$ ions are formed at anode.

None of the above ions discharge at anode ; instead Ni atoms of the anode lose electrons to form $Ni^{2+}$ ions.

Assertion: HCl does not conduct electricity in the gas phase.
Reason: HCl does not dissociate properly into ions in the gas phase.
chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

  1. Both Assertion and Reason are true and Reason is the correct explanation of Assertion

  2. Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

  3. Assertion is true but Reason is false

  4. Assertion is false but Reason is true

  5. Both Assertion and Reason are false

Show answer
Correct Option: A
Explanation:

It is HCl having unique property which does not conduct electricity when it is in gas phase since the gas phase of HCl is in the form of molecules and not in ionic form, the anhydrous HCl gas does not conduct electricity. But HCl solution or Aq HCl conducts electricity since HCl completely dissociates in solution to form Hydronium $H _3O^+$ and $Cl^-$ ions which are getting transported into opposite direction when potential electric junction is created by applying differential voltage, thus migration of these ions in opposite directions to each other allows electricity and thus becomes conductor of electricity.