CBSE Questions for Class 12 Engineering Chemistry Electrochemistry Quiz 4 - MCQExams.com

For which of these redox pairs, the reduction potential vary with pH
  • $$AmO_2^{2+} / AmO_2^{+}$$
  • $$AmO_2^{2+} / Am^{4+}$$
  • $$MnO_4^-/ Mn^{2+}$$
  • $$Zn^{2+} / Zn$$
The passage of electricity in the Daniell cell when $$Zn$$ and $$Cu$$ electrodes are connected:
  • from $$Cu$$ to $$Zn$$ inside the cell
  • from $$Cu$$ to $$Zn$$ outside the cell
  • from $$Zn$$ to $$Cu$$ outside the cell
  • none of the above
Molten $$AlCl_3$$ is electrolysed with the current of $$0.5 $$ empere to produced 27 g $$Al$$. Number of Farady used are :
  • $$3$$
  • $$5$$
  • $$6$$
  • None of these
An apparatus used for the measurement of the quantity of electricity passed is known as a:
  • calorimeter
  • cathetometer
  • coulometer
  • colorimeter
In electrolysis experiment, after some times, the battery connection is reversed. Then 
  • The electrolysis will stop
  • the rate of liberation of material at electrodes will increase
  • the rate of liberation will decrease
  • rate of liberation will remain unchanged
  • more heat will be produced at the electrodes
The charge carriers in metallic conductors and in electrolytes are respectively:
  • both ions
  • both electrons
  • electrons and ions
  • ions and electrons
Which of the following statements is/are incorrect ?
  • Rust is $$Fe_{2}O_{3}$$
  • Zn - Cu cell is called Daniell cell.
  • Saline water slows down rusting.
  • Pure metals undergo corrosion faster than impure metals.
Iron can be prevented from rusting by:
  • connecting iron to more electropositive metal a case of cathodic protection.
  • connecting iron to more electropositive metal a case of anodic protection.
  • connecting iron to less electropositive metal a case of anodic protection.
  • connecting iron to less electropositive metal a case of cathodic protection.
Electrolysis of aqueous solutions  of which of the following substances results in only the decomposition of water ? 
  • Potassium chloride
  • Zinc sulphate
  • Potassium hydroxide
  • Sodium phosphate
In the atmosphere of industrial smog, copper corrodes to form:
  • Basic copper carbonate
  • Copper sulphide
  • Basic copper sulphate
  • Copper oxide

How many coulombs are required for the oxidation of 1 mol of $$H_2O \ to \ O_2$$?
  • $$93000 C$$
  • $$1.93\, \times\, 10^5 C$$
  • $$9.65\, \times\, 10^4 C$$
  • $$19.3\, \times\, 10^2 C$$
$$E^{\ominus}\, for\, Cr^{3+}\, +\, 3e^-\, \rightarrow\, Cr\,\space and \space Cr^{3+}\, +\, e^-\, \rightarrow\, Cr^{2+}$$ are $$-0.74 V$$ and $$-0.40 V$$, respectively. $$E^{\ominus}$$ for the reaction is: $$Cr^{+2}\, +\, 2e^-\, \rightarrow\, Cr$$
  • $$-0.91 V$$
  • $$+0.91 V$$
  • -$$1.14 V$$
  • $$+0.34 V$$
Electrolysis can be used to determine atomic masses. A current of $$0.550$$  A deposits $$0.55 $$ g of a certain metal in $$100$$ minutes. Calculate the atomic mass of the metal is $$ n = 3$$ :
  • $$100$$
  • $$45.0$$
  • $$48.25$$
  • $$144.75$$
A magnet is pulled away from a conducting coil in a circuit. The direction of the induced emf in the coil can be found from...........
  • Faraday's law of electromagnetic induction
  • Joule's law
  • Lenz's law
  • Fleming's left hand rule
Which of the following statement is correct-
  • $$E_{cell} $$ & $$\Delta_r G$$ of cell reaction are extensive properties
  • $$E_{cell} $$ & $$\Delta_r G$$ of cell reaction are intensive properties
  • $$E_{cell}$$ is an intensive property while $$\Delta_rG$$ of cell reaction is an extensive property
  • $$E_{cell}$$ is an intensive property while $$\Delta_rG$$ of cell reaction is an intensive property
Same quantity of current is passed through molten NaCl and molten $$Al_{2}O_{3}$$. If 4.6 g of Na was deposited in one cell, the mass of Al deposited in other cell is:-
  • 0.9 g
  • 1.8 g
  • 2.7 g
  • 3.6 g
Charge produced in butane $$-O_{2}$$ Fuel cell if $$2\ mol$$ butane is consumed, will be
  • $$23 F$$
  • $$49 F$$
  • $$26 F$$
  • $$52 F$$
The standard reduction potentials of $$Cu^{2+}\, |\, Cu$$ and $$Cu^{2+}\, |\, Cu^{\bigoplus}$$ are 0.337 V and 0.153 V, respectively. The standard electrode potential of $$Cu^{\bigoplus}\, |\, Cu$$ half cell is:
  • 0.184 V
  • 0.827 V
  • 0.521 V
  • 0.490 V
In an electrolytic cell current flows:
  • from cathode to anode in outer circuit
  • from anode to cathode outside the cell
  • from cathode to anode inside the cell
  • none of the above
On the basis of the electrochemical theory of aqueous corrosion, the reaction occurring at the cathode is :
  • $$O_{2(g)}+4H_{(aq)}^{+}+4e^{-}\rightarrow 2H_{2}O_{(l)}$$
  • $$Fe_{(s)}\rightarrow Fe_{(aq)}^{2+}+2e^{-}$$
  • $$Fe_{(aq)}^{2+}\rightarrow Fe_{(aq)}^{3+}+e^{-}$$
  • $$H_{2(g)}+2OH_{(aq)}^{-}\rightarrow 2H_{2}O_{(l)}+2e^{-}$$
Write true or false for the following statements : 
A solution of an ionic compound in water contains ions , which move to the opposite electrodes when electricity is passed through the solution. 
  • True
  • False
Write true or false for the following statements : 
At ordinary temperature, the surface of metals such as magnesium, aluminium, zinc, lead, etc., are covered with a thin layer of oxide which protects the metals from the further oxidation. 
  • True
  • False
Calcium oxide reacts vigorously with water to produce:
  • Calcium hydroxide releasing a large amount of heat.
  • Calcium hydroxide absorbing a large amount of heat.
  • Calcium oxide and hydrogen with a release of large amount of heat.
  • Calcium oxide any hydrogen with a absorption of large amount of heat
Write true or false for the following statements:
Due to corrosion iron gets a brown coating, copper gets a green coating and silver gets a black coating.
  • True
  • False
Calculate $$\Delta G$$ for the following cell reaction.
$$Zn_{(s)}+ Ag_2O_{(s)} + H_2O_{(l)} \rightarrow Zn^{2+} _{(aq)} + 2Ag_{(s)} +2OH{^-}{_{(aq)}}$$

$${ E }_{ { { Ag }^{ + } }/{ Ag }  }^{ 0 }=+0.80V$$   and   $${ E }_{ { { Zn }^{ +2 } }/{ Zn }  }^{ 0 }=-0.76V$$
  • $$-305\ {kJ}/{mol}$$
  • $$-301\ {kJ}/{mol}$$
  • $$305\ {kJ}/{mol}$$
  • $$301\ {kJ}/{mol}$$
What is not Avogadro's number ?
  • The number of atoms in 11.2 L of $$\displaystyle { O }_{ 2 }$$ at STP
  • The number of atoms in 1 mole of $$\displaystyle He$$ at STP
  • The number of electrons in 96,500 coulombs
  • The number of $$\displaystyle { SO }_{ 4 }^{ 2- }$$ ions in 1 L of 0.5 M sulphuric acid
  • None of the above
When $$0.1$$ mol $$MnO_4^{2-}$$ is oxidised the quantity of electricity required to completely $$MnO_4^{2-}$$ to $$MnO_4{^-}$$ is:
  • $$96500\ C$$
  • $$2\times 96500\ C$$
  • $$9650\ C$$
  • $$96.50\ C$$
1C electricity deposits:
  • 10.8 g of Ag
  • electrochemical equivalent of Ag
  • half of electrochemical equivalent of Ag
  • 96500 g of Ag
An electrode connected to the positive terminal of a battery is called anode.
  • True
  • False
Anode in the galvanic cell is :
  • Negative electrode
  • Positive electrode
  • Neutral electrode
  • None of the above
Current in an electrolyte is carried by
  • only electrons
  • only - ve ions
  • only + ve ions
  • both + ve and - ve ions
Electric energy is produced by the :
  • separation of charges
  • separation of protons
  • separation of holes
  • separation of plates
When the lead accumulator is charged, it acts as:
  • an electrolytic cell
  • a galvanic cell
  • a Daniel cell
  • none of the above
According to the electrochemical concept, corrosion occurs at :
  • anodic area of metal
  • cathodic area of metal
  • both cathodic and anodic areas of metal
  • neither cathodic area nor anodic areas of metal
As dilution of the solution increases then the conductivity of solution ___________.
  • increases
  • decreases
  • remain unchanged
  • none of the above
A constant voltage is applied between the two ends of a uniform metallic wire. Some heat is developed in it. The heat developed is double if:
  • both the length and radius of wire are halved
  • both length and radius of wire are doubled
  • the radius of wire is doubled
  • the length of the wire is doubled
Splitting up of the water molecule by an electric current is an example of electrolysis.
  • True
  • False
For reducing one mole of $$Cr_{2} O_{7}^{2-}$$ to $$Cr^{3+}$$, the charge required is:
  • $$3\times 96500\ coulomb$$
  • $$6\times 96500\ coulomb$$
  • $$0.3\ Faradays$$
  • $$0.6\ Faradays$$
When the power delivered by a $$100$$ volt battery is $$40$$ watts, the equivalent resistance of the circuit is:
  • $$100\;ohms$$
  • $$250\;ohms$$
  • $$300\;ohms$$
  • $$350\;ohms$$
The internal resistance of a lead acid battery can be reduced by
  • Using strips of wood or celluloid as separators between electrodes
  • Using grids of hard lead-antinomy alloy
  • Using a specific manner of assembly of electrodes with wood or celluloid separators in between
  • Both option A and B
The charge required for the reduction of $$1\ mol$$ of $${MnO_{4}}^{-}$$ to $$MnO_{2}$$ is:
  • $$1\ F$$
  • $$3\ F$$
  • $$5\ F$$
  • $$6\ F$$
Three copper wires of lengths and cross sectional areas are $$(\ell,\,A),\,(2\,\ell,\,A/2)$$ and $$(\ell/2,\,2A)$$. Resistance is minimum in:
  • wire of cross-sectional area $$A/2$$
  • wire of cross-sectional area A
  • wire of cross-sectional area $$2A$$
  • same in all the three cases
The $$ZnCl$$ used in a dry cell is which helps to maintain the moistness of paste contained in the cell between anode and cathode is
  • Highly hydroscopic
  • Weak hydroscopic
  • Strongly hydrophobic
  • Weak hydrophobic
Faraday law of electrolysis indirectly shows
  • Quantisation of charge
  • Quantisation of angular momentum
  • Quantisation of current
  • Quantisation of viscosity
When a corroded metal object is rubbed by a sand paper then:
  • outer metal surface is removed
  • metal becomes thin
  • outer corroded layer will be removed
  • all of the above
The standard reduction potential for $$Mg^{2+}/Mg$$ is $$-2.37V$$ and for $$Cu^{2+}/Cu$$ is $$0.337$$. The $$E^o_{cell}$$ for the following reaction is $$Mg+Cu^{2+}\rightarrow Mg^{2+}+Cu$$
  • $$+2.03V$$
  • $$-2.03V$$
  • $$-2.7V$$
  • $$+2.7V$$
Electrolytes which allow large current to pass through them are known as :
  • weak electrolytes
  • strong electrolytes
  • non-electrolytes
  • none of the above
_____________ ionizes in a fused or in aqueous solution state and furnish positive ions other than $$H^+$$ and negative ions other than $$OH^-$$.
  • Mineral acids
  • Bases
  • Ionic salts
  • Compounds
A metal is released in the electrolysis of a salt. It gets deposited on the :
  • sides of the container
  • half of positive terminal and half of negative terminal
  • negative terminal
  • positive terminal
______ ionizes in fused or in aqueous solution state and furnish ions in solution.
  • Mineral acids
  • Bases
  • Ionic salts
  • Compounds
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