CBSE Questions for Class 12 Engineering Chemistry Electrochemistry Quiz 11 - MCQExams.com

In a galvanic cell:
  • chemical reaction produces electrical energy
  • electrical energy produces chemical reaction
  • reduction occurs at anode
  • oxidation occurs at cathode
For the cell prepared from electrode A and B, electrode A : $$\dfrac { { Cr }_{ 2 }{ O }_{ 7 }^{ 2- } }{ { Cr }^{ 3+ } } $$, $${ E }_{ red }^{ 0 }$$ = +1.33 V and electrode B : $$\dfrac { {Fe}^{ 3+ } }{ { Fe }^{2+}}$$ ,  $${ E }_{ red }^{ 0 }$$ = 0.77 V, which of the following statement is  not correct ?
  • The electrons will flow from B to A (in the outer circuit) when connections are made
  • The standard e.m.f. of the cell will be 0.56 V
  • A will be positive electrode
  • None of the above
Which of the following statements is wrong about galvanic cells?
  • Cathode is the positive electrode
  • Cathode is the negative electrode
  • Electrons flow from anode to cathode in the external circuit
  • Reduction occurs at cathode
Galvanisation is a method of protecting iron from rusting by coating with a thin layer of
  • Gallium
  • Aluminium
  • Zinc
  • Silver
If copper is kept open in air, it slowly loses its shining brown surface and gains a green coating. It is due to the formation of
  • $$CuSO_4$$
  • $$CuCO_3$$
  • $$Cu(NO_3)_2$$
  • $$CuO$$
The mass of ions deposited during a given interval of time in the process of electrolysis depends on 
  • The current
  • The resistance
  • The temperature
  • The electric power
If 96500 coulombs of electricity liberates one gram equivalent of anysubstance, the time taken for a current of 0.15 amperes to deposite20mg of copper from a solution of copper sulphate is (Chemicalequivalent of copper = 32)
  • 5 min 20 sec
  • 6 min 42 sec
  • 4 min 40 sec
  • 5 min 50 sec
In electrolysis, if the duration of the passage of current is doubled, the mass liberated is 
  • Doubled
  • Halved
  • Increased
  • Remains the same
In the process of electrolysis, the current is carried out inside the electrolyte by
  • Electrons
  • Atoms
  • Positive and negative ions
  • All the above
The compound $$75$$ decomposed into its constituents under the effect of electric current is called:
  • Electrolysis
  • Hydrolysis
  • Electroplating
  • Corrosion
To deposit one gm equivalent of an element at an electrode, the quantity of electricity needed is 
  • One ampere
  • $$96000 $$ amperes
  • $$96500 $$ farads
  • $$96500$$ coulombs
E.C.E. of Cu and Ag are$$7\times 10^{-6}$$ and $$1.2\times 10^{-6}$$ certain current deposits 14 gm of Cu. Amount of Ag deposited is
  • 1.2 gm
  • 1.6 gm
  • 2.4 gm
  • 1.8 gm
The chemical equivalent of copper and zinc are 32 and 108 respectively. When copper and silver voltameter are connected in series and electric current is passed through for sometimes, 1.6 g of copper is deposited. Then, the mass of silver deposited will be
  • 3.5 g
  • 2.8 g
  • 5.4 g
  • None of these
Water can not be conducting by adding small amount of any of the following except 
  • Sodium chloride
  • Copper sulphate
  • Ammonium chloride
  • Sugar

The electrochemical cell stops working after some time because:
  • electrode potentials of both electrodes becomes zero
  • electrode potentials of both electrodes becomes equal
  • temperature of the cell increases
  • the reaction starts proceeding in opposite direction
In producing chlorine through electrolysis $$100$$ watt power at 125 V is being consumed. How much chlorine per minute is liberated ? Electrochemical Equivalent of chlorine is $$0.367$$ $$\times$$ 10$$^{-6}$$ kg/coulomb:
  • $$21.3$$ mg
  • $$17.6$$ mg
  • $$24.3$$ mg
  • $$13.6$$ mg

During conductometric titration of 0.1 M HCl with 1.0 M KOH, which of the following will be observed?
  • Resistance of the solution decreases upto equivalence point and then increases
  • Resistance of the solution increases upto equivalence point and then decreases
  • Conductance increases upto equivalence point and then decreases
  • Conductance decreases upto equivalence point and then becomes almost constant
Given, $$\mathrm{E}_{\mathrm{F}\mathrm{e}^{3+}/\mathrm{F}\mathrm{e}}^{o}= -0.036\mathrm{V},\ \mathrm{E}_{\mathrm{F}\mathrm{e}^{2+}/\mathrm{F}\mathrm{e}}^{o}= -0.439 \mathrm{V}$$. The value of standard electrode potential for the change, $$\mathrm{F}\mathrm{e}^{3+}(\mathrm{a}\mathrm{q})+\mathrm{e}^{-}\rightarrow \mathrm{F}\mathrm{e}^{2+}(\mathrm{a}\mathrm{q})$$ will be:
  • $$-0.403\mathrm{V}$$
  • $$0.385 \mathrm{V}$$
  • $$0.770\mathrm{V}$$
  • $$-0.270\mathrm{V}$$
What is the standard electrode potential for the electrode $$MnO{_{4}}^{-}/MnO_{2}$$ in the solution?
Given: $$E{^{o}}_{MnO{_{4}}^{-}/Mn^{2+}}=1.51V$$ and $$E{^{o}}_{MnO_{2}/Mn^{2+}}=1.23V$$:
  • $$1.70 V$$
  • $$-1.70 V$$
  • $$5.10 V$$
  • $$-5.10 V$$
$$Cu^{+}$$ is not stable and undergoes disproportionation. $$E^{o}$$ for $$Cu^{+}$$ disproportionation is : $$(E^{o}_{Cu^{2+}/Cu^{+}}=+0.153V,\ E{^{o}}_{Cu^{+}/Cu} =0.53V)$$
  • +0.683 V
  • -0.367 V
  • +0.3415 V
  • +0.377 V

A resistance of 50 $$\Omega$$ is registered when two electrodes are suspended into a beaker containing a dilute solution of a strong electrolyte such that exactly half of the them are submerged into solution. If the solution is diluted by adding pure water (negligible conductivity) so as to just completely submerge the electrodes, the new resistance offered by the solution would be:

114916.jpg
  • 50 $$\Omega$$
  • 100 $$\Omega$$
  • 25 $$\Omega$$
  • 200 $$\Omega$$
In a daniel cell, if $$A(E^o = -0.76 \ C)$$ and $$B(E^o = -2.36 \ V)$$ half cells are taken then:
  • $$B$$ acts as anode
  • $$A$$ acts as anode
  • $$B$$ acts as cathode
  • cannot be predicted

Given standard electrode potentials:

$$Fe^{3+}+3e^{-}\rightarrow Fe;E^{0}=-0.036V$$

$$Fe^{2+}+2e^{-}\rightarrow Fe;E^{0}=-0.440V$$

The standard electrode potential $$E^o$$ for $$Fe^{3+}+e^-\rightarrow Fe^{2+}$$ is:
  • 0.476 V
  • 0.404 V
  • 0.40 V
  • +0.772 V
Select the correct statements about the electrolysis.
  • Electric current is used to drive a non spontaneous reaction.
  • $$\Delta G$$ is positive for chemical process during electrolysis.
  • Cations and anions move towards the anode and cathode respectively.
  • Over voltage is generally associated with the anode in the electrolysis of $$NaCl (aq)$$.
The electrode potentials for $$Cu^{2+}_{(aq)} + e^{-} \rightarrow Cu_{(aq)}^{+}$$ and $$Cu_{(aq)}^{+} + e^{-} \rightarrow Cu_{(s)}$$
Are $$+0.15 V$$ and $$+0.50 V$$ respectively.
The value of $$E_{Cu^{2+}/Cu}^{\circ}$$ will be
  • $$0.500 V$$
  • $$0.325 V$$
  • $$0.650 V$$
  • $$0.150 V$$
In Nickel-Silver nitrate cell, silver acts as a :
  • cathode
  • anode
  • salt bridge
  • none of these
Stand electrode potential are;
$$Fe^{+2}$$/Fe                 E = 0.44 
$$Fe^{+3}/Fe^{+2}$$          E = 0.77 
If $$Fe^{+2}, Fe^{+3}$$ and Fe block re kept together, then:
  • $$Fe^{+3}$$ increases
  • $$Fe^{+3}$$ decreases
  • $$\displaystyle \frac{Fe^{+2}}{Fe^{+3}}$$reamins unchanged
  • $$Fe^{+2}$$ decreases
$$Al_2O_3$$ is reduced by electrolysis at low potentials and high currents. If $$4.0 \times 10^4$$ amperes of current is passed through molten $$Al_2O_3$$ for 6 hours, what mass of aluminium is produced? (Assume 100% current efficiency, at. mass of $$Al = 27 g \;mol^{-1})$$
  • $$1.3 \times 10^4\;g$$
  • $$9.0 \times 10^3\;g$$
  • $$8.1 \times 10^4\;g$$
  • $$2.4 \times 10^5\;g$$
Lithium cell comes under category of :
  • non-disposable battery
  • disposable battery
  • lithium battery
  • lead acid battery
Which is true according to the Faraday Law of electrolysis? Here $$m$$ is the mass deposited at an electrode, $$Q$$ is the charge at the electrode and $$I$$ is the current passed.
  • $$m\propto { I }^{ 2 }$$
  • $$m\propto Q$$
  • $$m\propto { Q }^{ 2 }$$
  • $$m$$ does not depend on $$Q$$
The given diagram shows an electrochemical cell in which the respective half cells contain aqueous 1.0 M solutions of the salts $$XCl_2$$ and $$YCl_3$$. Given that, 

$$3X_{(s)} + 2Y^{3+}_{(aq)} \rightarrow 3X^{2+}_{(aq)} + 2Y_{(s)},\ E_{cell}> 0$$

Which of the following statement(s) is/are correct?

72200.png
  • The electrode made from metal X has positive polarity.
  • Electrode Y is the anode.
  • The flow of electrons is from Y to X.
  • The reaction at electrode X is an oxidation reaction.
In a voltaic cell, if iron and silver electrodes are connected with each other then current flows:
  • from iron to silver outside the cell
  • from silver to iron within the cell
  • from silver to iron outside the cell
  • current does not flow in this cell
Calculate the useful work of the reaction $$Ag(s) + 1/2 Cl_2 (g)    \rightarrow AgCl(s)$$.
Given $$E_{cl_2 / Cl^-}^0 = + 1.36 V,$$ $$E_{Ag|AgCl|Cl^-}^0 = 0.22 V$$ if $$P_{Cl_2} = 1  \ atm$$ and $$T= 298 K$$.
  • 110 kJ/mol
  • 220 kJ/mol
  • 55 kJ/mol
  • 1000 kJ/mol
The E$$^o$$ in the given diagram is:

114892.jpg
  • 0.523
  • 0.613
  • 0.715
  • 0.825
State True or False.
Batteries are voltaic cells.
  • True
  • False
Battery charging equipment is generally installed:
  • in well ventilated location.
  • in clean and dry place.
  • as near as practical to the battery being charged.
  • in location having all above features.
    A fuel cell develops an electrical potential from the combustion of butane at $$1\space bar$$ and $$298\space K$$.$$\quad C_4H_{10}(g)+6.5O_2(g) \longrightarrow 4CO_2(g)+5H_2O(l); \quad \triangle_rG^{\small\circ} = -2746\space kJ/mol$$
    What is $$E^{\small\circ}$$ of a cell?
  • $$4.74\space V$$
  • $$0.547\space V$$
  • $$4.37\space V$$
  • $$1.09\space V$$
For a reaction in a galvanic cell, the value of $$-\triangle G^{\small\circ}$$ at certain temperature is not necessarily equal to:
  • $$nFE^{\small\circ}$$
  • $$RT\space ln\space K$$
  • $$T\triangle S^{\small\circ} - \triangle H^{\small\circ}$$
  • $$\text zero$$
The indication of the state of charge of a battery is best given by:
  • specific gravity of electrolyte
  • temperature of electrolyte
  • colour of electrolyte.
  • level of electrolyte.
Internal resistance of a battery cell decreases with :
  • an increase in area of the plates inside the electrolyte
  • an increase in distance between the two electrodes
  • a decrease in size of the electrodes
  • an increase of age of the battery
Standard electrode potential of two half-reactions are given below:
$$ Fe^{2+}\rightleftharpoons Fe; \quad                      E^{\small\circ} = -0.44\space V$$
$$ Fe^{3+}\rightleftharpoons Fe^{2+}; \quad              E^{\small\circ} = +0.77\space V$$

If $$Fe^{2+},\space Fe^{3+}$$ and $$Fe$$ are kept together :
  • the concentration of $$Fe^{3+}$$ increases
  • the concentration of $$Fe^{3+}$$ decreases
  • the mass of $$Fe$$ increases
  • the concentration of $$Fe^{2+}$$ decreases
Chromium metal can be plated out from an acidic solution containing $$CrO_{3}$$, according to the following equation.

       $$CrO_{3}(aq)+6H^{+} +6e^- \rightarrow Cr(s)+3H_{2}O$$
   
 How many grams of chromium will be plated out by $$24000$$ coulombs?
  • $$0.78\ g$$
  • $$0.45\ g$$
  • $$1.2\ g$$
  • None of these
Quinhydrone half cell is not reversible to:
  • H$$^+$$
  • quinone
  • quinol
  • OH$$^-$$
One Faraday is the amount of current:
  • that liberates 1 g equivalent of a metal from its solutiion
  • 96515 coulomb
  • that liberates 31.78 g of Cu
  • that liberates 1/2 g-atom of Cu
Select the correct statements about galvanic cells.
  • Electrons are fed into anode by the oxidation reaction that takes place at the electrode.
  • The anode pushes these electrons into the external circuit and thus, acts as a source of negative charge.
  • The cathode acts as an electron sink and thus, called positive electrode.
  • The algebraic sum of E$$_{OP}$$ of anode and E$$_{OP}$$ of cathode gives the +ve value for spontaneous process.
The $$E^o_{cell} $$ for $$Cu | Cu^{2+}$$ in volt is:
  • $$0.35$$
  • $$-0.35$$
  • $$+0.325$$
  • $$-0.325$$
$$Cu^{\oplus}\, +\, e^-\, \rightarrow\, Cu,\, E^{\ominus}\, =\, x_1$$ volt
$$Cu^{2+}\, +\, 2e^-\, \rightarrow\, Cu,\, E^{\ominus}\, =\, x_2$$ volt, then for
$$Cu^{2+}\, +\, e^-\, \rightarrow\, Cu,\, E^{\ominus}$$ (volt) will be:
  • $$x_1\, -\, 2x_2$$
  • $$x_1\, +\, 2x_2$$
  • $$x_1\, -\, x_2$$
  • $$2x_1\, -\, x_1$$
Given the standard potential of the following at $$25^{\circ}C$$. $$MnO_{2}\, \rightarrow\, Mn^{3+}$$; $$E^{\ominus}\, =\, 0.95\, V$$
$$Mn^{3+}\, \rightarrow\, Mn^{2+}$$; $$E^{\ominus}\, =\, 1.51\, V$$
The standard potential of $$MnO_{2}\, \rightarrow\, Mn^{2+}$$ is:
  • $$-0.56 V$$
  • $$-2.46 V$$
  • $$-1.23 V$$
  • $$1.23 V$$
Which of the following is used as electrodes in batteries?
  • Diamond
  • Graphite
  • Activated charcoal
  • Carbon black
For the reaction :
$$4Al(s)\, +\, 3O_{2}(g)\, +\, 6H_{2}O\, +\, 4\, \overset{\ominus}{O}H\, \rightarrow\, 4[Al(OH)_{4}]^{\oplus}$$
$$E^{\ominus}_{cell}\, =\, 2.73\, V$$
If $$\Delta_{f}G^{\ominus}\, [\overset{\oplus}{O}H]\, =\, -\, 157\, kJ\, mol^{-1}$$;
$$\Delta_{f}G^{\ominus}\, (H_{2}O)\, =\, -\, 237.2\, kJ\, mol^{-1}$$.
The value of $$\Delta_{f}G^{\ominus}\, [Al(OH)_{4}]^{\ominus}$$ is:
[free energy of formation of $$(Al(OH)_{4}^{\ominus}]$$.
  • $$\Delta_{f}G^{\ominus}[Al(OH)_{4}]^{\ominus}\, =\, + 3.50\, \times\, 10^{3}\, kJ\, mol^{-1}$$
  • $$\Delta_{f}G^{\ominus}[Al(OH)_{4}]^{\ominus}\, =\, + 2.40\, \times\, 10^{3}\, kJ\, mol^{-1}$$
  • $$\Delta_{f}G^{\ominus}[Al(OH)_{4}]^{\ominus}\, =\, - 1.30\, \times\, 10^{3}\, kJ\, mol^{-1}$$
  • $$None \:\:of \:\:these $$
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