Tag: electrolytic cells and electrolysis

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Questions Related to electrolytic cells and electrolysis

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

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
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.
Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.
$4OH^- \rightarrow 2H _2O + O _2 \uparrow + 4e^-$

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

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 $Na^{+}+e^{-}\rightarrow Na$

  1. a and b are correct

  2. c,d are correct

  3. only c is correct

  4. all are correct
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis
Aqueous solution of nickel sulphate contains $Ni^{2+}$ and ${SO _{4}}^{2-}$ ions. What will be the product at the nickel anode?
  1. $Ni^{2+}$
  2. ${SO _{4}}^{2-}$
  3. $Ni$
  4. $H _2SO _4$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

At the anode, oxidation occurs. Nickel metal (the anode) loses electrons to form Ni2+ ions, which dissolve into the solution.

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

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

  1. $Ni^{2+}$
  2. ${SO _{4}}^{2-}$

  3. both A and B

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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