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

During the electrolysis of an aqueous solution of $HCOOK$, the number of gases obtained at cathode, anode, and a total number of gases are:

  1. $1, 2, 3$
  2. $1, 2, 2$
  3. $2, 1, 3$
  4. $2, 1, 2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

At cathode:
$\displaystyle H _2O\, +\, e^-\, \rightarrow\, \overset{\ominus}O H\, +\, \frac{1}{2} H _2\, (one)$
At anode:
$2HCOO^{\ominus}\, \rightarrow\, 2CO _2\, +\, H _2\, (two)$
$H _2\, and\, CO _2$ at anode and $H _2$ at cathode

With the total number of gases $2$

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

Name the process from which chlorine is obtained as by product. What will happen if an aqueous solution of NaCl is subjected to electrolysis.

  1. Haber process, $NaOH, H _2, Cl _2$
  2. Down cell process, Na metal and $Cl _2$ gas are obtained
  3. Down cell process, $NaOH, H _2, Cl _2$

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Haber process is used for producing ammonia from nitrogen and hydrogen.
Down's Process. Molten NaCl upon electrolysis will give Na metal and $Cl _2$ gas. Aqueous NaCl will form NaOH,$H _2 , Cl _2$.

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

If aq. NaCl is electrolysed using graphite as anode and Hg as cathode than products are:

  1. $\displaystyle Cl _{2}$ gas at anode and Na at cathode
  2. $\displaystyle Cl _{2}$ gas at anode and $\displaystyle H _{2}$ gas at cathode
  3. $\displaystyle O _{2}$ gas at anode and $\displaystyle H _{2}$ gas at cathode
  4. $\displaystyle Cl _{2}$ gas at anode and $\displaystyle O _{2}$ gas at cathode
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If aq. $NaCl$ is electrolyzed using graphite as anode and $Hg$ as cathode then products are $Cl _2$ gas at anode and $Na$ at the cathode.

In the presence  of Hg electrode the over voltage of $H _2$ is very high and reduction of $H _2O$ is possible.

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

The products formed when an aqueous solution of $NaBr$ is electrolysed in a cell having inert electrodes are :

  1. $Na$ and $Br _{2}$
  2. $Na$ and $O _{2}$
  3. $H _{2}, Br _{2}$ and $NaOH$
  4. $H _{2}$ and $O _{2}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$NaBr\rightleftharpoons Na^{+} + Br^{-}$
$2H _{2}O + 2e\rightarrow H _{2} + 2OH^{-}$
$Na^{+} + OH^{-} \rightarrow NaOH$ At cathode
$Br^{-}\rightarrow Br + e^{-}$
$Br + Br \rightarrow Br _{2}$ At anode
So the products are $H _{2}$ and $NaOH$ (at cathode) and $Br _{2}$ (at anode).

Hence, option C is correct option.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis
Which of the following will not produce an electrolytic solution upon addition of water?
  1. $N _2(g)$
  2. $HCl(g)$
  3. $KOH(s)$
  4. $NaI(s)$
  5. $CaCl _2(s)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When water is added, HCl, KOH, NaI and $CaCl _2$ will produce an electrolytic solution. However, $N _2$ will not produce an electrolytic solution on addition of water. Nitrogen is a homo-nuclear diatomic molecule which does not dissociate into aqueous solution.

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

Electrolysis of which of the following compound will give $KOH$?

  1. Aqueous $KCl$ solution
  2. Fused $KCl$

  3. Fused potassium

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

Electrolysis of aqueous $KCl$ solution will give $KOH$. This is similar to the preparation of $NaOH$ by electrolysis of aqueous $NaCl$ solution. The electrolysis of fused $KOH$ will give potassium metal.

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

A solution containing one mole per lite of each $Cu(NO {3}) _{2}; AgNO _{3}; Hg _{2}(NO _{3}) _{2}$ and $Mg(NO _{3}) _{2}$ is being electrolysed by using inert electrodes. The values of standard electrode potentials (reduction potentials) are $Ag/ Ag^{+} = 0.80\ volt, 2Hg/ H _{2}^{2+} = 0.79\ volt, Cu/ Cu^{2+} = + 0.24\ volt, Mg/ Mg^{2+} = -2.37\ volt$. With increasing voltage, the sequence of deposition of metals on the cathode will be___________.

  1. $Ag, Hg, Cu$
  2. $Cu, Hg, Ag$
  3. $Ag, Hg, Cu, Mg$
  4. $Mg, Cu, Hg, Ag$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Higher the standard reduction potential, higher will be the tendency to undergo reduction so, more fast will be its deposition on electrode (cathode) .

$E^o _{Ag/Ag^+}=0.80V\ E^o _{2Hg/Hg _2^{2+}}=0.79V\quad \downarrow (Reduction\quad potential\quad decreases)\ E^o _{Cu/Cu^{2+}}=0.24V$    
Order of deposition= $Ag> Hg> Cu$

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

The emf of a cell containing sodium/ copper electrodes is $3.05\ V$, if the electrode potential of copper electrode is $+0.34\ V$, the electrode potential of sodium is:

  1. $-2.71\ V$
  2. $+ 2.71\ V$
  3. $-3.71\ V$
  4. $+3.71\ V$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
$E _{cell}^{\circ}=E _{cathode}^{\circ}-E _{anode}^{\circ}$
$\Rightarrow3.05=0.34-(-2.71)$
$=3.05$
$\therefore$ Electrode potential of Sodium is $-2.71V$