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Redox and electrode processes - class-XI

Questions covering Daniel/Daniell cell electrochemistry including electrode potentials, EMF calculations, redox reactions, electron flow, and Faraday's laws of electrolysis.

20 Questions Published
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Questions

Question 1 Multiple Choice (Single Answer)

The life span of a Daniel cell may increased by:

  1. large Cu electrode
  2. lowering of CuSO$ _{4}$ concentration
  3. lowering of ZnSO$ _{4}$ concentration
  4. large zinc electrode
Question 2 Multiple Choice (Single Answer)

Estimate the cell potential of a Daniel cell having $1.0 M - Zn^{2+}$ and originally having $ 1.0 M - Cu^{2+}$ after sufficient ammonia has been added to the cathode compartment to make the $ NH _{3}$ concentration 2.0 M. Given: $ _{zn^{2+}|Zn}^{0} = 0.76 V, E _{Cu^{2+}|Cu}^{0} = + 0.34 V, K _{f}$ for $ Cu (NH _{3}) _{4}^{2+} = 1 \times 10^{12}.$

  1. 1.10 V
  2. 0.704 V
  3. 0.396 V
  4. 1.496 V
Question 3 Multiple Choice (Multiple Answers)

The passage of electricity in the Daniel cell when Zn and Cu electrodes are connected 

  1. from Cu to Zn inside the cell
  2. from Cu to Zn outside the cell
  3. from Zn to Cu inside the cell
  4. from Zn to Cu outside the cell
Question 4 Multiple Choice (Single Answer)

In a Daniel cell when $Cu$ and $Zn$ electrodes are connected current flows from:

  1. $Cu$ to $Zn$ within the cell
  2. $Cu$ to $Zn$ outside the cell
  3. $Zn$ to $Cu$ outside the cell
  4. all of the above
Question 5 Multiple Choice (Single Answer)

In the electrochemical cell $H _{2}(g),1atm|H^{+}(1M)||Cu^{2+}(1M)|Cu(s)$, which one of the following statements is true? 

  1. H$ _{2}$ is cathode, Cu is anode
  2. Oxidation occurs at Cu electrode
  3. Reduction occurs at H$ _{2}$ electrode
  4. H$ _{2}$ is anode, Cu is Cathode
Question 6 Multiple Choice (Single Answer)

The standard EMF of a Daniel cell at 298 K is $E _{1}$. When the concentration of $ZnSO _{4}$ is 1.0 M and that of $CuSO _{4}$ is 0.01 M, the EMF becomes $E _{2}$ at 298 K. The correct relationship between $E _{1}$ and $E _{2}$ is

  1. $E _{1} = E _{2}$
  2. $E _{2}=0$
  3. $E _{1} > E _{2}$
  4. $E _{1} < E _{2}$
Question 7 Multiple Choice (Single Answer)

If a current of 1.0 A is drawn from the Daniel cell for 96.5 min, the cathode will gain in weight by (Cu = 63.5, Zn = 65.4)

  1. 1.905 g
  2. 1.962 g
  3. 3.81 g
  4. 3.924 g
Question 8 Multiple Choice (Single Answer)

If a battery of $1.6V$ is connected to Daniel cell, current flows:

  1. into the cell
  2. out of the cell
  3. neither in nor out of the cell
  4. both ways
Question 9 Multiple Choice (Single Answer)

Electrochemical Battery

An electrochemical battery is a device powered by oxidation and reduction reactions that are physically separated. So that the electrons must travel through a wire from the reducing agent to the oxidizing agent. 

The reducing agent loses electrons and is oxidized in a reaction that takes place at an electrode is called the anode. The oxidizing agent gains electrons and is reduced in a reaction that takes at an electrode is called the cathode.  

To maintain a net zero charge in each compartment, there is a limited flow of ions through a salt bridge. 
For example, in a car battery the reducing agent is oxidized by the following reaction, which involves a lead ( $Pb$ ) anode and sulfuric acid ( $H _2SO _4$). Lead sulfate ( $PbSO _4$ ), protons ( $H$ ), and electrons ( $e^-$) are produced.

At the cathode, the below reaction occurs :

$PbO _2+H _2SO _4+2H^++2e^-\rightarrow$ PbSO_4+2H_2O$
 
At the anode, the below reaction occurs :

$Pb+H_2SO_4 \rightarrow PbSO_4+2H^++2e^-$

Electrons are produced by a chemical reaction that takes place at the:

  1. anode.
  2. cathode.
  3. lead oxide electrode.
  4. oxidizer.
  5. salt bridge.
Question 10 Multiple Choice (Single Answer)
Assertion: In a Daniell cell, electrons flow from zinc electrode to copper electrode outside the cell.
Reason: In Daniell cell, Zn electrode is anode and Cu is cathode.
  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
Question 11 Multiple Choice (Single Answer)

For the cell $Zn(s)|Zn^{2+}(aq)||Cu^{+2}(aq)|Cu(s)$. The cell potential $E _{cell}$ can be increased.

  1. By increasing $[Cu^{+2}]$
  2. By increasing $[Zn^{+2}]$
  3. By decreasing $[Cu^{+2}]$
  4. By decreasing $[Zn^{+2}]$
Question 12 Multiple Choice (Single Answer)

In a Daniell cell:

  1. The chemical energy liberated during the redox reaction is converted to electrical energy
  2. The electrical energy of the cell is converted to chemical energy
  3. The energy of the cell is utilised in conduction of the redox reaction
  4. The potential energy of the cell is converted into electrical energy
Question 13 Multiple Choice (Multiple Answers)

Which one is not correct for e.m.f. of a galvanic cell?

  1. $E _{cell} = E _{OP _{anode}} + E _{RP _{cathode}}$
  2. $E _{cell} = E _{OP _{LHS}} + E _{RP _{RHS}}$
  3. $E _{cell} =$ higher oxidation potential - lower oxidation potential
  4. $E _{cell} =$ lower oxidation potential - higher oxidation potential
Question 14 Multiple Choice (Single Answer)

Identify the true statement regarding Daniel cell:

  1. Zinc ions flows across salt bridge
  2. ${K}^{+}$ ions move from salt bridge to $Cu/{Cu}^{+2}$ half cell
  3. Oxidation takes place at copper electrode
  4. Flow of current takes place from copper electrode to zinc electrode
Question 15 Multiple Choice (Single Answer)

For the galvanic cell, $Cu|Cu^{2+}||Ag^+|Ag$. Which of the following observations is not correct?

  1. Cu acts as anode and Ag acts as cathode
  2. Ag electrode loses mass and Cu electrode gains mass
  3. Reaction at anode, $Cu\rightarrow Cu^{2+}+2e^-$
  4. Copper is more reactive than silver
Question 16 Multiple Choice (Single Answer)

The negative Zn pole of Daniel cell, sending a constant current through a circuit, decreases in mass by 0.13 g in 30 minutes. If the chemical equivalent of Zn and Cu and 32.5 and 31.5 respectively, the increase in the mass of the positive Cu pole in this time is : 

  1. 0.180 g
  2. 0.141 g
  3. 0.126 g
  4. 0.242 g
Question 17 Multiple Choice (Single Answer)

The passage of electricity in the Daniell cell when $Zn$ and $Cu$ electrodes are connected is from:

  1. $Cu$ to $Zn$ in the cell
  2. $Cu$ to $Zn$ outside the cell
  3. $Zn$ to $Cu$ outside the cell
  4. $Zn$ to $Cu$ in the cell
Question 18 Multiple Choice (Single Answer)

Daniel cell operates under nonstandard state conditions. If the equation of the cell reaction is multiplied by 2 then:

  1. $E$ and $E^o$ remain unchanged
  2. $E$ is doubled
  3. $n$ remains unchanged in Nernst equation
  4. $Q$ is halved in Nernst equation
Question 19 Multiple Choice (Single Answer)

For the Daniel cell involving the cell reaction${ Zn } _{ (s) }+{ { Cu }^{ +2 } } _{ (aq) }\rightleftharpoons { { { Zn }^{ +2 } } } _{ (aq) }+{ Cu } _{ (s) }$ the standard free energies of formation of  ${ Zn } _{ (s) }$, ${ Cu } _{ (s) }$, ${ { Cu }^{ +2 } } _{ (aq) }$ and ${ { { Zn }^{ +2 } } } _{ (aq) }$ are 0, 0, 64.4 KJ/Mole and -154.0 KJ/Mole, respectively. Calculate the standard EMF of the cell?

  1. $2.13 Volts$
  2. $1.13 Volts$
  3. $2.26 Volts$
  4. $3.42 Volts$
Question 20 Multiple Choice (Single Answer)

Which of the following statement is TRUE for the electrochemical Daniel cell :

  1. Electron flow from Zinc electrode to Copper electrode.
  2. Current flows from zinc electrode to copper electrode.
  3. Cation moves towards copper electrode.
  4. Cation moves towards zinc electrode.
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