Tag: applications of redox reaction

Questions Related to applications of redox reaction

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

chemistry oxidation- reduction reactions redox reactions and electrode processes redox and electrode processes applications of redox reaction

  1. By increasing $[Cu^{+2}]$

  2. By increasing $[Zn^{+2}]$

  3. By decreasing $[Cu^{+2}]$

  4. By decreasing $[Zn^{+2}]$

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Correct Option: A

In a Daniell cell:

chemistry oxidation- reduction reactions redox reactions and electrode processes redox and electrode processes applications of redox reaction

  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

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Correct Option: A
Explanation:

A galvanic cell is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell. It generally consists of two different metals connected by a salt bridge, or individual half-cells separated by a porous membrane. Daniel cell is a galvanic cell.

Daniel cell has Zn as anode and Cu as cathode. The reactions of Daniel cell are,

At anode(Oxidation),

$Zn(s)\rightarrow Zn^{2+}(aq)+2e^{-}$

At cathode(Reduction),

$Cu^{2+}(aq)+2e^{-}\rightarrow Cu(s)$

Hence overall reaction is,

$Zn(s)+Cu^{2+}(aq)\rightarrow Zn^{2+}(aq)+Cu(s)$

Here the chemical energy is liberated when the redox reaction takes place in the cell and it is converted into electrical energy.

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

chemistry oxidation- reduction reactions redox reactions and electrode processes redox and electrode processes applications of redox reaction

  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

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Correct Option: A,B,C
Explanation:

The correct expressions for the standard cell potentials of a galvanic cell are as given below.
$E _{cell} = E _{OP _{anode}} + E _{OP _{cathode}}$
$E _{cell} = E _{OP _{LHS}} + E _{OP _{RHS}}$
$E _{cell} =$lower oxidation potential $-$ higher oxidation potential.
Thus, only option D is correct and options A to C are incorrect.

Identify the true statement regarding Daniel cell:

chemistry oxidation- reduction reactions redox reactions and electrode processes redox and electrode processes applications of redox reaction

  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

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Correct Option: D
Explanation:

Daniell cell is  perform the spontaneous redox reaction between zinc and cupric ions to produce an electric current. It consists of two half-cells. The  left half cell contains a zinc metal electrode dipped in $ZnSO _4$ solution.The half right half cell consists of copper metal electrode in a solution $CuSO _4$. The half-cells are joined by a salt bridge that prevents the mixing of the solution.
In Daniel cell flow of current takes place from copper electrode to zinc electrode.
Hence option D is correct.

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

chemistry oxidation- reduction reactions redox reactions and electrode processes redox and electrode processes applications of redox reaction

  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

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Correct Option: B
Explanation:

Redox reactions are reactions in which both oxidation and reduction takes place together. In a Galvanic cell oxidation occurs at anode and reduction occurs at cathode. Here $Cu$ is an anode and $Ag$ is a cathode. As in Oxidation, the electrons get released to form aqueous ions in the solution and hence reduces the mass of the electrode as the electrons are released from the electrode. Here,$Cu$ electrode loses mass. Similarly,the released electrons are gained by silver ions i.e $Ag^ { +} $ and the electrode mass of $Ag$ gets increased. Hence, B is the wrong option.

The number of equivalents of $Na _{2}S _{2}O _{3}$ required for the volumetric estimation of one equivalent of $Cu^{2+}$ is:

redox and stoichiometry applications of redox reaction oxidation- reduction reactions redox reactions chemistry

  1. $1/3$

  2. $1$

  3. $3/2$

  4. $2/3$

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Correct Option: B
Explanation:

Number of equivalents of reacting species in a chemical reaction are same.

A volume of $100 ml$ of $ H _{2}O _{2}$ is oxidized by 100 ml of $ 1 M \ KMnO _{4}$ in acidic medium $ (MnO _{4}^{-}$ reduced to $ Mn^{2+}).$ A volume of $100 ml$ of same $H _{2}O _{2}$ is oxidized by $'V'$ ml of $1 M \ KMnO _{4}$ in basic medium ($ MnO _{4}^{-}$ reduced to $ MnO _{2}).$ The value of $'V'$ is

redox and stoichiometry applications of redox reaction oxidation- reduction reactions redox reactions chemistry

  1. $500$

  2. $100$

  3. $33.33$

  4. $166.67$

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Correct Option: D
Explanation:

In acidic medium, 

$ N _{1}V _{1} = N _{2}V _{2} $

$ n _1\times M _{1}\times V _{1} = n _2\times M _{2}\times V _{2} $

$ 5\times 1\times 100 =  2\times M _{2} \times 100$ 

$ M _{2} = 2.5\,M $

Now in basic medium,

$ N _{1}V _{1} = N _{2}V _{2} $

$ 2\times 2.5 \times 100=  3\times 1\times V $

$ \therefore V = \dfrac{200\times 2.5}{3} $

$V = 166.66\,ml $

A solid $PQ$ has rock salt type structure in which $Q$ atoms are the corners of the unit cell. If the body-centered atoms in all the unit cells are missing, the resulting stoichiometry will be

redox and stoichiometry applications of redox reaction oxidation- reduction reactions redox reactions chemistry

  1. $PQ$

  2. $P{Q} _{2}$

  3. ${ P } _{ 3 }{ Q } _{ 4 }$

  4. ${ P } _{ 4 }{ Q } _{ 3 }$

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Correct Option: C

In a solid $AB$ of $NaCl$ structure, A atoms occupy the corners of the cubic unit cell. If all the corner atoms are removed then the formula of the unit cell will be

redox and stoichiometry applications of redox reaction oxidation- reduction reactions redox reactions chemistry

  1. $A _{4}B _{4}$

  2. $B$

  3. $A _{3}B _{4}$

  4. $AB$

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Correct Option: C

Number of electrons involved in the electrodeposition of 63.5 g of Cu from solution of $ CuSO _{4} $ is:

redox and stoichiometry applications of redox reaction oxidation- reduction reactions redox reactions chemistry

  1. $ 6.022\times 10^{23} $

  2. $ 3.011\times 10^{23} $

  3. $ 12.044\times 10^{23} $

  4. $ 6.022\times 10^{23} $

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Correct Option: C
Explanation:
$ Cu^{2+}+2e^-\rightarrow Cu $ 

1 mole Cu = 63.5 g
 
For deposition of 1 mole of Cu, 2 moles of $e^-$ is required.

$ \therefore$ Number of electrons $ =12.044\times 10^{23} $      
                                    
Hence, option C is correct.