Electrochemical Series

Q. Given, $E_{C{r}^{(}3+)/Cr}^0=-0.74V;E_{Mn{O}_4^{-}/M{n}^{2+}}^0=1.51V$
$E_{C{r}_2{O}_7^{2-}/C{r}^{3+}}^0=1.33V;E_{Cl/C{l}^{-}}^0=1.36V$
Based on the data given above strongest oxidising agent will be

1. $C{l}^{-}$
2. $C{r}^{3+}$
3. $M{n}^{2+}$
4. $Mn{O}_4^{-}$

Q.

Which is the Strongest Reducing Agent?

1. $\mathrm{Zn}\left(\mathrm{s}\right)$

2. $\mathrm{Cr}\left(\mathrm{s}\right)$

3. ${\mathrm{H}}_2\left(\mathrm{g}\right)$

4. ${\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)$

Q. Arrange $Zn$, $Pb$ and $Al$ in the decreasing order of their reducing powers under standard conditions.
Given: $E_{Z{n}^{2+}|Zn}^0=-0.76V,E_{P{b}^{2+}|Pb}^0=-0.13V$
$E_{A{l}^{3+}|Al}^0=-1.66V$

1. $Zn>Al>Pb$
   
2. $Al>Zn>Pb$
3. $A1>Pb>Zn$
4. $Zn>Al>Pb$

Q. Which of the following of metals, when coupled, will give maximum EMF for a voltaic cell?
Given:
$A{u}^{+}\left(aq\right)+e^{-}\to Au\left(s\right);E^0=1.69V$
$C{u}^{2+}\left(aq\right)+2e^{-}\to Cu\left(s\right);E^0=0.34V$
$P{b}^{2+}\left(aq\right)+2e^{-}\to Pb\left(s\right);E^0=-0.13V$
$F{e}^{2+}\left(aq\right)+2e^{-}\to Fe\left(s\right);E^0=-0.44V$
$C{a}^{2+}\left(aq\right)+2e^{-}\to Ca\left(s\right);E^0=-2.87V$

1. $Fe\text{and}Au$
2. $Pb\text{and}Au$
3. $Cu\text{and}Au$
4. $Ca\text{and}Cu$

Q.

Redox reactions play a pivotal role in chemistry and biology. The values of standard redox potential $\left(E_{\ominus }\right)$ of two half cell reactions decided which way the reaction is expected to proceed. A simple example is a Daniell cell in which zinc goes into solution and copper gets deposited. Given below are a set of half cell reactions (acidic medium) along with their $E_{\ominus }$ (V with respect to normal hydrogen electrode) values. Using this data, obtain correct explanations for the following question
$I_2+2e^{-}\to 2I^{\ominus };E^{\ominus }=0.54$
$C{l}_2+2e^{-}\to 2C{l}^{\ominus };E^{\ominus }=1.36$
$M{n}^{3+}+e^{-}\to M{n}^{2+};E^{\ominus }=1.50$
$F{e}^{3+}+e^{-}\to F{e}^{2+};E^{\ominus }=0.77$
$O_2+4H^{⨁}+4e^{-}\to 2H_{2}O;E^{\ominus }=1.23$

While $F{e}^{3+}$ is stable, $M{n}^{3+}$ is not stable in acid solution because

1. $O_{2}oxidizesM{n}^{2+}toM{n}^{3+}$

2. $O_{2}oxidizesbothM{n}^{2+}toM{n}^{3+}andF{e}^{2+}toF{e}^{3+}$

3. $F{e}^{3+}oxidizes{H}_{2}Oto{O}_2$

4. $M{n}^{3+}oxidizes{H}_{2}Oto{O}_2$

Q.

Ivana the Innovative decided to make a new electrochemical series taking the $Z{n}^{2+}/Zn$ electrode as the base standard, considering its reduction potential as 0 and calculating all others relative to it.
Statement 1 - It is possible to do such a thing.
Statement 2 - We need to calculate relative values because absolute values cannot be determined.

1. Both 1 and 2 are true

2. Both 1 and 2 are false

3. 1 is false and 2 is true

4. 2 is false and 1 is true

Q. The standard reduction potentials at 298 K for the following half reactions are given:

Which is the strongest reducing agent?
$Z{n}^{2+}(aq.)+2e\rightleftharpoons Zn\left(s\right);-0.762$
$C{r}^{3+}\left(aq\right)+3e\rightleftharpoons Cr\left(s\right);-0.740$
$2H^{+}\left(aq\right)+2e\rightleftharpoons H_2\left(g\right);0.00$
$F{e}^{3+}\left(aq\right)+e\rightleftharpoons F{e}^{2+}\left(aq\right);0.770$

1. $Zn\left(s\right)$
2. $Cr\left(s\right)$
3. $H_2\left(g\right)$
4. $F{e}^{2+}\left(aq\right)$

Q.

For the reduction of $N{O}_3^{\ominus }$ ion in an aqueous solution, $E^{\ominus }$ is +0.96 V, the values of $E^{\ominus }$ for some metal ions are given below:
$\left(i\right)V^{2+}\left(aq\right)+2e^{-}\to V;E^{\ominus }=-1.19V$
$\left(ii\right)F{e}^{3+}\left(aq\right)+3e^{-}\to Fe;E^{\ominus }=-0.04V$
$\left(iii\right)A{u}^{3+}\left(aq\right)+3e^{-}\to Au;E^{\ominus }=+1.40V$
$\left(iv\right)H{g}^{2+}\left(aq\right)+2e^{-}\to Hg;E^{\ominus }=+0.86V$

The pair(s) of metals that is/are oxidized by $N{O}_3^{\ominus }$ in aqueous solution is/are
(IIT-JEE, 2010)

1. $Fe$ and $Au$

2. $Hg$ and $Fe$

3. $V$ and $Hg$

4. $Fe$ and $V$

Q. An aqueous solution containing one mole per litre of each $Cu(N{O}_3{)}_2,AgN{O}_3,H{g}_2(N{O}_3{)}_2$ and $Mg(N{O}_3{)}_2$, is being electrolysed by using inert electrodes. The values of standard electrode potentials in volts (reduction potentials) are $Ag/A{g}^{+}=+0.80,2Hg/H{g}_2^{2+}=+0.79,Cu/C{u}^{2+}=+0.34,Mg/M{g}^{2+}=-2.37$ with increasing voltage, the sequence of deposition of metals on the cathode will be

1. $Ag,Hg,Cu,Mg$
2. $Mg,Cu,Hg,Ag$
3. $Ag,Hg,Cu$
4. $Cu,Hg,Ag$

Q. Electrochemical series gives the order of reduction potentials of elements and ions in an increasing/decreasing trend.

1. True
2. False

Q. Carbon-based reduction is NOT used for the extraction of:

1. Tin from $Sn{O}_2$
2. Iron from $F{e}_2{O}_3$
3. Aluminium from $A{l}_2{O}_3$
4. Magnesium from $MgC{O}_3.CaC{O}_3$

Q. You want to store a freshly made solution of copper sulphate. You have 4 options with you. Which of these is preferable to ensure that the solution remains intact?
Reduction potentials:
$Z{n}^{2+}/Zn=-0.76$
$M{g}^{2+}/Mg=-2.37$
$C{u}^{2+}/Cu=0.34$
$A{g}^{+}/Ag=0.8$
$S{n}^{2+}/Sn=0.16$

1. Zinc vessel
2. Magnesium vessel
3. Tin vessel
4. Silver vessel

Q. What will be the effect on emf of given cell when the concentration of $A{g}^{+}$ at cathode is decreased to $0.1M$?
$Ag\left(s\right)|A{g}^{+}(aq,0.001M)||A{g}^{+}(aq,1M)|Ag\left(s\right)$

1. Emf of the cell gets reduced from $0.177$ to $0.118V$
2. Emf of the cell increased from $0.117$ to $3.31V$
3. Emf of the cell gets reduced from $0.214$ to $0V$
4. Emf of the cell increased from $0.118$ to $0.214V$

Q. The metal that cannot be produced on reduction of it's oxide by aluminium is:-

1. K
2. Mn
3. Cr
4. Fe

Q. Carbon-based reduction is NOT used for the extraction of:

1. Tin from $Sn{O}_2$
2. Iron from $F{e}_2{O}_3$
3. Aluminium from $A{l}_2{O}_3$
4. Magnesium from $MgC{O}_3.CaC{O}_3$

Q. You want to store a freshly made solution of copper sulphate. You have 4 options with you. Which of these is preferable to ensure that the solution remains intact?
Reduction potentials:
$Z{n}^{2+}/Zn=-0.76$
$M{g}^{2+}/Mg=-2.37$
$C{u}^{2+}/Cu=0.34$
$A{g}^{+}/Ag=0.8$
$S{n}^{2+}/Sn=0.16$

1. Zinc vessel
2. Magnesium vessel
3. Tin vessel
4. Silver vessel

Q. The metal that cannot be produced on reduction of it's oxide by aluminium is:-

1. K
2. Mn
3. Cr
4. Fe

Q.
For the reduction of $N{O}_3^{-}$ ion in an aqueous solution $E^{\circ }$ is +0.96 V. Values of $E^{\circ }$ for some metal ions are given below:
$V^{2+}\left(aq\right)+2e^{-}\to V;E^0=-1.19V$
$F{e}^{3-}\left(aq\right)+3e^{-}\to Fe;E^{\circ }=-0.04V$
$A{u}^{3+}\left(aq\right)+3e^{-}\to Au;E^{\circ }=+1.40V$
$H{g}^{2+}\left(aq\right)+2e^{-}\to Hg;E^0=+0.86V$
The pair(s) of metals that is/are oxidised by $N{O}_3^{-}$ in aqueous solution is (are)

1. V and Hg
2. Hg and Fe
3. Fe and Au
4. Fe and V

Q.
For the reduction of $N{O}_3^{-}$ ion in an aqueous solution $E^{\circ }$ is +0.96 V. Values of $E^{\circ }$ for some metal ions are given below:
$V^{2+}\left(aq\right)+2e^{-}\to V;E^0=-1.19V$
$F{e}^{3-}\left(aq\right)+3e^{-}\to Fe;E^{\circ }=-0.04V$
$A{u}^{3+}\left(aq\right)+3e^{-}\to Au;E^{\circ }=+1.40V$
$H{g}^{2+}\left(aq\right)+2e^{-}\to Hg;E^0=+0.86V$
The pair(s) of metals that is/are oxidised by $N{O}_3^{-}$ in aqueous solution is (are)

1. V and Hg
2. Hg and Fe
3. Fe and Au
4. Fe and V