Tag: chemistry

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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.

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

A gas which does not conduct electricity in the liquid state but conducts electricity when dissolved in water is :

  1. $HCl$.
  2. $H _2$.
  3. $SO _2$.
  4. $Cl _2$.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
It is HCl having a 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 Aquous $HCl$ 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.
Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

Assertion: $NH _3$ gas conduct electricity.
Reason: $NH _3$ dissociates 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
E Correct answer
Explanation

$NH _3$ doesnt conducts electricity in gaseous form but in solution form due to formation of $NH _4^+,  OH^-$ ions, it conducts electricity.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis
Assertion: Sodium cannot be obtained by the electrolysis of aqueous solution of NaCl using Pt electrodes.
Reason: In the aqueous NaCl solution, $H _2O$ will get reduced during 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
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Correction : in question sodium cannot be obtained. In aqueous solution , it is $H _2O$ which is reduced.
$2H _2O + 2e^{-} \rightarrow 2H _2 + 2\overset {\ominus}{O} H$

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

In Down's process for the manufacture of sodium, $CaCl _2$ is added to:

  1. decrease the melting point

  2. increase the melting point

  3. decrease the interionic interactions

  4. increase the interionic interactions
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$CaCl _2$ is added to lower the melting point from 1080 K (melting point of NaCl) to 850 K. This is due to following reasons.
a. At such high temperature, it is very difficult to maintain Na in the molten state during electrolysis.
b. Moreover, Na is voltile at this temperature and a part of it would vapourize.
c. Molten Na, gets dispersed in molten NaCl to form metallic fog at high temperature.
d. Both Na and $Cl _2$ produced in the electrolysis have a corrosive action on the vessel used.
The over all reactions nare as follows :
At cathode : $Na^{\oplus} + e^{-} \rightarrow Na$
At anode : $Cl^{\ominus} \rightarrow \displaystyle \frac{1}{2} Cl _2 + e^{-}$