CBSE Questions for Class 12 Engineering Chemistry Electrochemistry Quiz 9 - MCQExams.com

Consider the following equations for a cell reaction
$$A + B \rightleftharpoons  C+D$$  $$ E^0=x\,volt,k_{eq}=k_1$$
$$2A+2B \rightleftharpoons  2C+2D $$ $$E^0=y\, volt,k_{eq}=K_2$$ then: 
  • $$x=y,K_1=k_2$$
  • $$x=2y,K_1=2k_2$$
  • $$x=y,K^2_1=k_2$$
  • $$x^2=y,K^2_1=k_2$$
$$H_{2}(g)$$ and $$O_{2}(g)$$, can be produced by the electrolysis of water. What total volume (in $$L$$) of $$O$$ and $$H_{2}$$ are produced at $$STP$$ when a current of $$30\ A$$ is passed through a $$K_{2}SO_{4}(aq)$$ solution for $$193\ min.$$?
  • 20.16
  • 40.32
  • 60.48
  • 80.64
6.5 g $$Mg$$ deposits on electrolysis of $$MgCl_2$$ (fused) then what will be the volume of chlorine gas at STP discharged at electrode?
  • 6.067 L
  • 3.033 L
  • 9.1 L
  • 12.133 L
An electrolytic cell is composed of $$Cu$$ and $$Zn$$. A current of $$9.65\ A$$ is drawn from a cell for $$1$$ hour. Then the loss in mass at anode and gain in mass at cathode, respectively could be:
  • $$11.77\ g, 11.43\ g$$
  • $$11.77\ g, 10\ g$$
  • $$22.86\ g, 23.54\ g$$
  • $$23.54\ g, 22.86\ g$$
For the cell prepared from electrode $$A$$ and $$B$$, electrode $$A:$$ $$\displaystyle\frac{Cr_2O^{2-}_7}{Cr^{3+}}$$, $$E^0_{red}=+1.33$$V and electrode $$B:$$ $$\displaystyle\frac{Fe^{3+}}{Fe^{2+}}$$, $$E^0_{red}=0.77$$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
  • Current flows from B to A in external circuit.
A gas $$X$$ at $$1\ atm$$ is bubbled through a solution containing a mixture of $$1\ M$$ $${ Y }^{ - }$$ and $$1\ M$$ $${ Z }^{ - }$$ ions at $$25^{\circ} C$$. If the reduction potential of $$Z > Y > X$$, then _____________.
  • Y will oxidize X and not Z
  • Y will oxidize Z and not X
  • Y will oxidize both X and Z
  • Y will reduce both X and Z
Standard reduction potentials of the half reactions are given below
$$\displaystyle F_{2(g)} + 2e^- \rightarrow 2F^{-}_{(aq)}$$;       $$E^o = +2.85V$$
$$\displaystyle Cl_{2(g)} + 2e^- \rightarrow 2Cl^{-}_{(aq)}$$;       $$E^o = +1.36V$$
$$\displaystyle Br_{2(l)} + 2e^- \rightarrow 2Br^{-}_{(aq)}$$;       $$E^o = +1.06V$$
$$\displaystyle I_{2(s)} + 2e^- \rightarrow 2I^{-}_{(aq)}$$;       $$E^o = +0.53V$$
The strongest oxidising and reducing agents respectively are:
  • $$F_2$$ and $$I^-$$
  • $$Br_2$$ and $$Cl^-$$
  • $$Cl_2$$ and $$Br^-$$
  • $$Cl_2$$ and $$I_2$$
Four faradays of electricity were passed through $${AgNO}_3$$, $${CdSO}_4$$, $${AICI}_3$$ and $${PbCI}_4$$ kept in four vessels using insert electrodes. The ratio of moles of Ag, Cd, AI and Pb deposited will be ?
  • 12 : 4 : 6 : 3
  • 1 : 2 : 3 : 4
  • 12 : 6 : 4 : 3
  • 4 : 3 : 2 : 1
The time required for a current of 3 ampere to decompose electrolytically 18 g of $$H_{2}O$$ is:
  • 18 hour
  • 36 hour
  • 9 hour
  • 18 second
Question No.60
Indicate the wrong statement according to Valence bond theory:
  • A sigma bond is stronger then $$\pi$$ - bond
  • p-orbitals always have only sidewise overlapping
  • s-orbitals never form $$\pi$$ - bonds
  • There can be only one sigma bond between two atoms
Read the passage given below and answer the question:
Chemical reactions involve the interactions of atoms and molecules. A large number of atoms/molecules (approximately $$6.023 \times 10^{23}$$) are present in few grams of any chemical compound varying with their atomic/molecular masses. To handle such large numbers conveniently, the mole concept was introduced. This concept has implications in diverse areas such as analytical chemistry,  biochemistry, electrochemistry, and radiochemistry. the following example illustrates a typical case, involving chemical/electrochemical reaction, which requires a clear understanding of the mole concept.
A 4.0 molar aqueous solution of NaCl is prepared and 500 mL of this solution is electrolyzed. This leads to the evolution of chlorine gas at one of the electrodes (atomic mass: Na = 23, Hg = 200; 1 faraday =96500 coulombs). 
The total charge (coulombs) required for complete electrolysis is:
  • 24125
  • 48250
  • 96500
  • 193000
1000 mL 1 M $$CuSO_4(aq)$$ is electrolysed by 9.65 amp current for 100 sec using $$Pt-$$electrode. Which is incorrect statement?
  • Blue colour intensity decreases during electrolysis
  • Blue colour intensity remains constant if $$Cu-$$electrode used
  • $$pH$$ of solution is 8 after electrolysis
  • At anode $$O_2$$ gas liberated during electrolysis
Spacecraft like the satellites that circle the earth and are used in television transmission have electric batteries that supply power for various purposes. These batteries contain ion-exchange resins instead of a liquid electrolyte solution because:
  • of extreme cold conditions
  • of lack of oxygen
  • a high electric voltage is required
  • of zero gravity
For the cell $$M/ M^{+} || X^{-}/ X, E^{\circ}_{M^{+}/ M} = 0.44$$ and $$E_{X/ X^{-}}^{\circ} = 0.33\ V$$. From the data it can be deduced that $$M + X\rightarrow M^{+} + X^{-}$$ is spontaneous.
  • $$M + X\rightarrow M^{+} + X^{-}$$ is spontaneous
  • $$E_{Cell} = 0.77\ V$$
  • $$E_{Cell} = -0.77\ V$$
  • None
Which of the following metals has been used for building boats because it has resistance to corrosion by sea water?
  • Copper
  • Nickel
  • Fungsten
  • Titanium
Iron nails rust fast when used for fixing plates or strips of aluminium on a building. Similarly, a water pipe made of iron corrodes faster when connected to a pipe of copper. This happens because of the?
  • Greater wetting of iron
  • Easier flow of electrons to iron
  • Higher rusting power of iron
  • Chemical reduction of iron
The standard reduction potential for the half-cell reaction, $$Cl_2+2e^-\rightarrow 2Cl^-$$ will be:
$$Pt^{2+}+2Cl^-\rightarrow Pt+Cl_2, E^o_{cell}=-0.15$$V;
$$Pt^{2+}+2e^-\rightarrow Pt, E^o=1.20$$V
  • $$-1.35$$V
  • $$+1.35$$V
  • $$-1.05$$V
  • $$+1.05$$V
Match the column I with column II and mark the appropriate choice.
Column I
Column II
(A)Electrochemical equivalent(i)Potential difference x Quantity of charge
(B)Faraday(ii)Mass of substance deposited by one coulomb of charge
(C)Ampere(iii)Charge carried by one mole of electrons
(D)Electrical energy(iv)One coulomb of electric charge passed through one second
  • (A)$$\rightarrow$$(ii), (B)$$\rightarrow$$ (i), (C)$$\rightarrow$$ (iii), (D)$$\rightarrow$$ (iv)
  • (A)$$\rightarrow$$ (ii), (B)$$\rightarrow$$ (iii), (C)$$\rightarrow$$ (iv), (D)$$\rightarrow$$ (i)
  • (A)$$\rightarrow$$ (iii), (B)$$\rightarrow$$ (iv), (C)$$\rightarrow$$ (i), (D)$$\rightarrow$$ (ii)
  • (A)$$\rightarrow$$ (iv), (B)$$\rightarrow$$ (i), (C)$$\rightarrow$$ (ii), (D)$$\rightarrow$$ (iii)
How much electricity in terms of Faraday is required to produce $$100$$g of Ca from molten $$CaCl_2$$?
  • $$1$$ F
  • $$2$$ F
  • $$3$$ F
  • $$5$$ F
Electrical conductance through metals is called metallic or electronic conductance and is due to the movement of electrons. The electronic conductance depends on:
  • the nature and structure of the metal
  • the number of valence electrons per atom
  • change in temperature
  • all of these
Which of the following is the correct cell representation for the given cell reaction?
$$Zn+H_2SO_4\rightarrow ZnSO_4+H_2$$
  • $$Zn|Zn^{2+}||H^+|H_2$$
  • $$Zn|Zn^{2+}||H^+, H_2|Pt$$
  • $$Zn|ZnSO_4||H_2SO_4|Zn$$
  • $$Zn|H_2SO_4||ZnSO_4|H_2$$
A galvanic cell has electrical potential of $$1.1$$ V. If an opposing potential of $$1.1$$ V is applied to this cell, what will happen to the cell reaction and current flowing through the cell?
  • The concentration of reactants becomes unity and current flows from cathode to anode
  • The cell does not function as a galvanic cell and zinc is deposited on zinc plate
  • The reaction stops and no current flows through the cell
  • The reaction continuous but current flows in opposite direction
A current of $$1.40$$ ampere is passed through $$500$$mL of $$0.180$$M solution of zinc sulphate for $$200$$ seconds. The molarity of $$Zn^{2+}$$ ions after deposition of zinc is:
  • $$0.154$$M
  • $$0.177$$M
  • $$2$$M
  • $$0.180$$M
How long would it take to deposit $$50$$g of $$Al$$ from an electrolytic cell containing $$Al_2O_3$$ using a current of $$105$$ ampere?
  • $$1.54$$ h
  • $$1.42$$ h
  • $$1.32$$ h
  • $$2.15$$ h
If a current of $$1.5$$ ampere flows through a metallic wire for $$3$$ hours, then how many electrons would flow through the wire?
  • $$2.25\times 10^{22}$$ electrons
  • $$1.13\times 10^{23}$$ electrons
  • $$1.01\times 10^{23}$$ electrons
  • $$4.5\times 10^{23}$$ electrons
When water is added to an aqueous solution of an electrolyte, what is the change in specific conductivity of the electrolyte?
  • Conductivity decreases
  • Conductivity increases
  • Conductivity remains same
  • Conductivity does not depend on number of ions
How many coulombs of electricity is required to reduce $$1$$ mole of $$Cr_2O^{2-}_7$$ in acidic medium?
  • $$4\times 96500$$ C
  • $$6\times 96500$$ C
  • $$2\times 96500$$ C
  • $$1\times 96500$$ C
The given figure shows the corrosion of iron in atmosphere.

Fill in the blanks by choosing an appropriate option.
At a particular spot of an object made of iron, $$\underline{(i)}$$ of iron to ferrous ion takes place and that spot behaves as $$\underline{(ii)}$$. Electrons released at $$\underline{(i)}$$ spot move through the metal and go to another spot on the metal and reduce oxygen in presence of $$H^+$$. This spot behave as $$\underline{(iii)}$$. The ferrous ions are further oxidised by atmospheric oxygen to ferric ions which come out as rust, $$\underline{(iv)}$$ and with further production of $$\underline{(v)}$$ ions.

934136_700f5d3299b046f2b319292c8ef4c411.png
  • (i)- Oxidation, (ii)- Anode, (iii)-Cathode, (iv)- $$Fe_2O_3.xH_2O$$, (v)-Hydrogen
  • (i)- Reduction, (ii)-Cathode, (iii)-Anode, (iv)-$$Fe_3O_4$$, (v)-Hydrogen
  • (i)-Oxidation, (ii)-Cathode, (iii)-Anode, (iv)-$$Fe_2O_3xH_2O$$, (v)-Hydrogen
  • (i)-Oxidation, (ii)-Anode, (iii)-Cathode, (iv)-$$Fe_2O_3\cdot H_2O$$, (v)-Ferrous
The electrode potential is the tendency of metal:
  • to gain electrons
  • to lose electrons
  • to either lose or gain electrons
  • none of these
Which of the following reactions does not take place during rusting?
  • $$H_2CO_3\rightleftharpoons 2H^++CO^{2-}_3$$
  • $$4Fe^{2+}+O_{2(dry)}\rightarrow Fe_2O_3$$
  • $$4Fe^{2+}+O_2+4H_2O\rightarrow 2Fe_2O_3+8H^+$$
  • $$Fe_2O_3+xH_2O\rightarrow Fe_2O_3\cdot xH_2O$$
Which metal is usefull for protection of iron by corrosion?
  • Aluminium
  • Sodium
  • Zinc
  • Copper
During electrolysis of a solution of $$AgNO_3$$, $$9650$$ coulombs of charge is passed through the solution. What will be the mass of silver deposited on the cathode?
  • $$108$$g
  • $$10.8$$g
  • $$1.08$$g
  • $$216$$g
Which of the statements about solutions of electrolysis is not correct?
  • Conductivity of solution depends upon size of ions
  • Conductivity depends upon viscosity of solution
  • Conductivity does not depend upon solvation of ions present in solution
  • Conductivity of solution increases with temperature
How many electrons are there in one coulomb of electricity?
  • $$

    6.023 \times 10^{23}

    $$
  • $$

    1.64 \times 10^{ 24}

    $$
  • $$

    6.24 \times 10^{ 18}

    $$
  • $$

    6.24 \times 10^{  24}

    $$
Which of the following metal do no evolve $${ H }_{ 2 }$$ gas from dil. acid?
  • $$A\left( { E }_{ { A }^{ + }/A }^{ o }=0.25V \right) $$
  • $$B\left( { E }_{ B/{ B }^{ + } }^{ 0 }=+0.22V \right) $$
  • $$C\left( { E }_{ { C }^{ + }/C }^{ 0 }=0.30V \right) $$
  • $$D\left( { E }_{ D/{ D }^{ + } }^{ 0 }=+0.44V \right) $$
For an electrochemical reaction occuring in a galvanic cell.
$$2{ Fe }_{ \left( aq \right)  }^{ +3 }+{ Zn }_{ \left( s \right)  }\rightarrow { Zn }_{ \left( aq \right)  }^{ +2 }+2{ Fe }_{ \left( aq \right)  }^{ +2 }$$
if concentration of $${ Fe }^{ +2 }$$ is increased.
  • $${E}_{cell}$$ will remain unchanged
  • $${E}_{cell}$$ will decrease
  • $$pH$$ of the solution will change
  • less non P-V work will be obtained

The approximate time duration in hours to electroplate $$30\space g$$ of calcium from molten calcium chloride using a current of $$5 \space A$$ is (At. mass of $$Ca = 40g/mol$$)
  • 80
  • 10
  • 16
  • 8
Consider the following equations for a cell reaction :
$$A  + B \rightarrow C + D \,; E^o = x \,volt, \Delta G = \Delta G_1$$
$$2A  +2 B \rightarrow 2C +2D \,; E^o = x \,volt, \Delta G = \Delta G_2$$
  • $$x = y, \Delta G_1 = \Delta G_2$$
  • $$x > y, \Delta G_1 > \Delta G_2$$
  • $$x = y, \Delta G_2 = 2\Delta G_1$$
  • $$x < y, \Delta G_2 = 2\Delta G_1$$
In which of the following conditions is the potential for the following half-cell reaction maximum?
$$2H^+ + 2e^{-} \longrightarrow H_2$$
  • $$1.0 \,M \,HCl$$
  • A solution having $$pH = 4$$
  • Pure water
  • $$1.0 \,M \,NaOH$$
Given that $$E^o_{Ag^+/Ag} = + 0.8V$$ and $$ E^o_{Ni^{+2}/Ni} = 0.25 V$$. Which of the following statement is true with regard to this?
  • $$Ag^+$$ is an oxidizing agent while $$Ni^{2+}$$ is a reducing agent
  • $$Ag^{2+}$$ can be reduced by silver metal
  • $$Ag^+$$ is a better oxidizing agent than $$Ni^{+2}$$ and $$Ni$$ is a better reducing agent that $$Ag$$
  • $$Ni^{2+}$$ is a better oxidizing agent than $$Ag^+$$ and $$Ag$$ is better reducing agent that $$Ni$$
Which of the following statements about the spontaneous reaction occurring in a galvanic cell is always true?
  • $$E^o_{cell} > 0, \Delta G^o < 0$$, and $$Q < K$$
  • $$E^o_{cell} > 0, \Delta G^o < 0$$, and $$Q > K$$
  • $$E^o_{cell} > 0, \Delta G^o > 0$$, and $$Q > K$$
  • $$E_{cell} > 0, \Delta G^o < 0$$, and $$Q < K$$
 Amount of charge is required to convert 17 gm $$H_2O_2$$ into $$O_2$$:-
  • 1 F
  • 2 F
  • 6 F
  • None of these
How many electrons flow when a current of 5 amperes passed through a solution for 193 seconds?
  • $$6.022\times { 10 }^{ 23 }$$
  • $$6.022\times { 10 }^{ 22 }$$
  • $$6.022\times { 10 }^{ 25 }$$
  • $$6.022\times { 10 }^{ 21 }$$
If equal quantities of electricity are passed through three voltmeter containing $$FeSO_4$$, $$Fe_2(SO_4)_3$$ and $$Fe(NO_3)_2$$, then which of the following is not true?
  • Amount of iron deposited in $$FeSO_4$$ and $$Fe_2(SO_4)_3$$ is equal
  • Amount of iron deposited in $$Fe(NO_3)_3$$ is $$\dfrac{2}{3}$$ of the amount of iron deposited in $$FeSO_4$$
  • Amount of iron deposited in $$Fe_2(SO_4)_3$$ and $$Fe(NO_3)_3$$ are equal
  • Same gas will evolve in all three cases at anode
Consider the reaction : $$Cr_2O^{2-}_{7} + 14H^+ + 6e^- \rightarrow 2Cr^{3+} + 7H_2O$$. 

What is the quantity of electricity in coulombs needed to reduce 1 mole of $$Cr_2O^{2-}_{7}$$ ?
  • $$579000\ C$$
  • $$679000\ C$$
  • $$879000\ C$$
  • $$979000\ C$$
In which one of the following one faraday of electricity will liberate 1/2 gram atom of the metal ?
  • $$AlCl_3$$
  • $$CuSO_4$$
  • $$FeCl_3$$
  • $$NaCl$$
The passage of a constant current through a solution of dilute $$H_2SO_4$$ with 'Pt' electrode liberated $$336cm^2$$ of a mixture of $$H_2$$ and $$O_2$$ at S.T.P. The quantity of electricity that was passed is:
  • 96500 C
  • 1965 C
  • 1930 C
  • 0.01 Faraday
The time required to produce 2F of electricity with a current of 2.5 amperes is:
  • 21.44 h
  • 1200 min
  • 50000 s
  • 1.5 h
The equilibrium constant for the following reaction at $$25^o$$C is $$2.9\times 10^9$$. Calculate standard voltage of the cell. 
$$Cl_{2(g)}+Br^-_{(aq)}\rightleftharpoons 2Cl^-_{(aq)}$$
  • $$0.18$$V
  • $$0.22$$V
  • $$0.26$$V
  • $$0.28$$V
A solution of $$Ni(NO_3)_2$$ is electrolyzed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode?
  • 1.622 gm
  • 1.722 gm
  • 1.822 gm
  • 1.922 gm
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