Electrochemical Series

Q.

Given the standard electrode potentials,
$K^{+}/K=-2.93V,A{g}^{+}/Ag=0.80V,H{g}^{2+}/Hg$
$=0.79V$
$M{g}^{2+}/Mg=-2.37V.C{r}^{3+}/Cr=-0.74V$
Arrange these metals in their increasing order of reducing power.

Q.

Arrange the following metals in the order in which they displace each other from the solution of their salts.

Al, Cu, Fe, Mg and Zn.

Q. The standard reduction potential for the half-cell reaction, $C{l}_2+2e^{-}\to 2C{l}^{-}$ if:
$P{t}^{2+}+2C{l}^{-}\to Pt+C{l}_2,E_{\text{cell}}^o=-0.15V$
$P{t}^{2+}+2e^{-}\to Pt,E^o=1.20V$

1. $-1.35\text{V}$
2. $+1.35\text{V}$
3. $-1.05\text{V}$
4. $+1.05\text{V}$

Q.

The standard reduction potentials at ${25}^0$ C of $L{i}^{+}$ /Li , $B{a}^{2+}$ /Ba , $N{a}^{+}$ /Na and $M{g}^{2+}$ /Mg are -3.05 , -2.73 , -2.71 and -2.37 volt respectively. Which one of the following is the strongest oxidizing agent?

1. Na⁺

2. Li⁺

3. Mg²⁺

4. Ba²⁺

Q. Standard electrode potentials of three metals $X,Y$ and $Z$ are $–1.2V,+0.5V$ and $–3.0V$ respectively. The reducing power of these metals will be:

1. $Y>Z>X$
2. $Y>X>Z$
3. $Z>X>Y$
4. $X>Y>Z$

Q. Consider the cell at ${25}^{o}C$
$Zn|Z{n}^{2+}\left(aq\right),\left(1M\right)||F{e}^{3+}\left(aq\right),F{e}^{2+}\left(aq\right)|Pt\left(s\right)$
The fraction of total iron present as $F{e}^{3+}$ ion at the cell potential of $1.500V$ is $x\times {10}^{-2}$. The value of $x$ is :
(Nearest integer)
Given:
$E_{F{e}^{3+}/F{e}^{2+}}^0=0.77V{E}_{Z{n}^{2+}/Zn}^0=-0.76V$

Q. Which of the following metal cannot be used for cathodic protection of $Fe$?

1. Zinc
2. Aluminium
3. Magnesium
4. Copper

Q.

The standard reduction potential data at ${25}^{\circ }C$ is given below.

$E^{\circ }\left(F{e}^{3+}/F{e}^{2+}\right)=0.77V;E^{\circ }\left(F{e}^{2+}/Fe\right)=-0.44V;E^{\circ }\left(C{u}^{2+}/Cu\right)=0.34V;E^{\circ }\left(C{u}^{+}/Cu\right)=+0.52V;E^{\circ }\left(O_2\right(g)+4H^{+}+4e^{-})\to 2H_{2}O=+1.23V;E^{\circ }\left(O_2\right(g)+2H_{2}O+4e^{-})\to 4O{H}^{-}=+0.40V{E}^{\circ }\left(C{r}^{3+}/Cr\right)=-0.74V;E^{\circ }\left(C{r}^{2+}/Cr\right)=+0.91V$

Match $E^{\circ }$ of the rebox pair in Column I with the values given in Column II and select the correct answer using the code given below the lists.

$\begin{array}{cc}ColumnI& ColumnII\\ P.E^{\circ }\left(F{e}^{3+}/Fe\right)& 1.-0.18V\\ Q.E^{\circ }(4H_{2}O\rightleftharpoons 4H^{+}+4O{H}^{-})& 2.-0.4V\\ R.E^{\circ }(C{u}^{2+}+Cu\to 2C{u}^{+})& 3.-0.04V\\ S.E^{\circ }\left(C{r}^{3+}/C{r}^{2+}\right)& 4.-0.83V\end{array}$

1. P - (4) Q - (1) R - (2) S - (3)

2. P - (1) Q - (2) R - (3) S - (4)

3. P - (3) Q - (4) R - (1) S - (2)

4. P - (2) Q - (3) R - (4) S - (1)

Q. In electrolysis of $NaCl$ when $Pt$ electrode is taken then $H_2$​ is liberated at the cathode while with $Hg$ cathode it forms sodium amalgam, because:

1. $Hg$ is more inert than $Pt$
2. More voltage is required to reduce $H^{+}$ at $Hg$ than at $Pt$
3. $Na$ is dissolved in $Hg$ while it does not dissolve in $Pt$
4. Concentration of $H^{+}$ ions is larger when $Pt$ electrode is taken
   

Q. why does lower E⁰ value is preferred at anode and higher at cathode?

Q. Given below some standard reduction potentials:
$S{n}^{2+}+2e^{-}\to Sn,E^{\circ }=-0.14V$
$H{g}_2^{2+}+2e^{-}\to 2Hg$, $E^{\circ }=0.79V$
Which of the following statement is correct?

1. $Hg$ can reduce $S{n}^{2+}$ to $Sn$
2. $S{n}^{2+}$ can oxidize $Hg$ to $H{g}_2^{2+}$
3. $H{g}_2^{2+}$ can oxidze $Sn$ to $S{n}^{2+}$
4. Between $H{g}_2^{2+}$ and $S{n}^{2+}$, $S{n}^{2+}$ is stronger oxidising agent than $H{g}_2^{2+}$

Q. Suggest a scheme of classification of the following redox reaction:

$A)$ $N_2\left(g\right)+O_2\left(g\right)⟶2NO\left(g\right)$

$B)$ $2Pb\left(N{O}_3{)}_2\right(s)⟶2PbO(s)+4N{O}_2(g)+O_2(g)$

$C)$ $NaH\left(s\right)+H_{2}O\left(l\right)⟶NaOH\left(aq\right)+H_2\left(g\right)$

$D\left)2N{O}_2\right(g)+2O{H}^{-}(aq)⟶N{O}_2^{-}(aq)+N{O}_3^{-}(aq)+H_{2}O(l)$

Q.

Assertion : Copper reacts with hydrochloric acid and liberates hydrogen from the solution of dilute hydrochloric acid.

Reason : Hydrogen is present below copper in the electrochemical series.

1. If both assertion and reason are true and the reason is the correct explanation of the assertion.
2. If both assertion and reason are true but reason is not the correct explanation of the assertion.
3. If assertion is true but reason is false.
4. If the assertion and reason both are false.

Q.

$E^{\ominus }$ values of some redox couples are given below. On the basis of these values choose the coorect option.
$E^{\ominus }$ values :

$\frac{B{r}_2}{B{r}^{-}}=+1.90\frac{A{g}^{+}}{Ag\left(s\right)}=+0.80\frac{C{u}^{2+}}{Cu\left(s\right)}=+0.34\frac{I_2\left(S\right)}{I^{-}}=+0.54;$

(a) Cu will reduce $B{r}^{-}$
(b) Cu will reduce $Ag$
(c) Cu will reduce $I^{-}$
(d) Cu will reduce $B{r}_2$

Q.

Write two basic requirements for refining of a metal by Mond process and by Van Arkel Method.

Q.

What is a redox reaction? Give two examples of redox reaction. Is it possible that a displacement reaction can be a redox reaction? Give examples of two redox reactions from your daily life.

Q.

The more positive the value of $E^{\ominus }$, the greater is the tendency of the species to get reduced. Using the standard electrode potential of redox couples given below find out which of the following is the strongest oxidising agent.

E\ominus values :

$\frac{F{e}^{3+}}{F{e}^{2+}}=+0.77\frac{I_2\left(S\right)}{I^{-}}=+0.54;\frac{C{u}^{2+}}{Cu}=+0.34;\frac{A{g}^{+}}{Ag}=0.80V$

(a) $F{e}^{3+}$
(b) $I_2\left(s\right)$
(c) $C{u}^{2+}$
(d) $A{g}^{+}$

Q.

Arrange the following metals in the order in which they displace each other from the solution of their salts. Al, Cu, Fe, Mg and Zn.

Q.

What are chemical reactions taking place inside a lead accumulator when it supplied electric current to an external resistance?

Q.

Using the standard electrode potential, find out the pair between which redox reaction is not feasible.

$E\ominus$values :

$\frac{F{e}^{3+}}{F{e}^{2+}}=+0.77\frac{I_2}{I^{-}}=+0.54;\frac{C{u}^{2+}}{Cu}=+0.34\frac{A{g}^{+}}{Ag}=+0.80V$

(a) $F{e}^{3+}$ and $I^{-}$
(b) $A{g}^{+}$ and Cu
(c) $F{e}^{3+}$ and Cu
(d) Ag and $F{e}^{3+}$

Q. When two half cells of electrode potential $E_1$ and $E_2$ combine to form a cell of electrode potential $E_3$ then choose the correct relation :
Here
$n_1,n_2\&n_3\text{are no. of electrons exhanged in first, second and combined half cells}$

1. $E_3=E_1-E_2$
2. $E_3=E_1+E_2$
3. $E_3=\frac{n_1{E}_1+n_2{E}_2}{n_3}$
4. $E_3=\frac{E_1+E_2}{n_1{n}_2{n}_3}$

Q. What is wrongly stated about electrochemical series

1. It is the representation of element in order of increasing or decreasing standard electrode reduction potential
2. It does not compare the relative reactivity of metals
3. It compares relative strengths of oxidizing agents
4. $H_2$ is centrally placed element

Q. Assertion: Copper sulphate can be stored in a zinc vessel.
Reason: Zinc is less reactive than copper.

Q.

Which of the following options are correct?

1. Zr and Ti are purified by van Arkel method.

2. Cast iron is obtained by remelting pig iron with scrap iron and coke using hot air blast.

3. Nickel is purified by zone refining.

4. In extraction of silver, silver is extracted as cationic complex.

Q. Using the standard potential values given below, decide which of the statements I, II, III, IV are correct. Choose the right answer from (a), (b), (c) and (d).
$F{e}^{2+}+2e^{-}\to Fe,E^{\circ }=-0.44V$
$C{u}^{2+}+2e^{-}\to Cu,E^{\circ }=+0.34V$
$A{g}^{+}+e^{-}\to Ag,E^{\circ }=+0.80V$
I. Copper can displace iron from $FeS{O}_4$ solution.
II. Iron can displace copper from $CuS{O}_4$ solution.
III. Silver can displace Cu from $CuS{O}_4$ solution.
IV. Iron can displace silver from $AgN{O}_3$ solution.

1. I and II
2. II and III
3. II and IV
4. I and IV

Q.

Which of the following reactions is an example of auto reduction?

1. 
2. 
3. 
4. 

Q.

Can you store copper sulphate solutions in a zinc pot?

Q. $\mathrm{The}\mathrm{reduction}\mathrm{potential}\mathrm{of}X\mathrm{is}\mathrm{greater}\mathrm{than}Y\mathrm{and}\mathrm{lower}\mathrm{than}Z.\mathrm{The}\mathrm{reduction}\mathrm{potential}\mathrm{of}W\mathrm{is}\mathrm{lower}\mathrm{than}Y.\mathrm{The}\mathrm{INCREASING}\mathrm{strengths}\mathrm{of}\mathrm{reducing}\mathrm{agents}\mathrm{is}:$

1. X
2. Y
3. Z
4. W

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

1. $V\text{and}Hg$
2. $Fe\text{and}Hg$
3. $Fe\text{and}Au$
4. $Fe\text{and}V$

Q.

Identify type of reaction:

$\mathrm{Cu}\left(\mathrm{s}\right)+\mathrm{S}\left(\mathrm{s}\right)\stackrel{\mathrm{heat}}{\to }\mathrm{CuS}\left(\mathrm{s}\right)$