(A) (a) The conductivity of $0.1\text{ mol L}^{-1}$ solution of $\text{NaCl}$ is $1.06 \times 10^{-2}\text{ S cm}^{-1}$. Calculate its molar conductivity and degree of dissociation.
$\lambda^\circ_{\text{Na}^+} = 50.1\text{ S cm}^2\text{ mol}^{-1}$
$\lambda^\circ_{\text{Cl}^-} = 76.5\text{ S cm}^2\t...
CBSE CLASS 12 • CHEMISTRY • CHAPTER 02
Electrochemistry
184 distinct questions across 224 board paper set appearances (2022–2026).
Electrochemistry is the study of the relationship between chemical energy and electrical energy. Many spontaneously occurring chemical reactions liberate electrical energy. In electrolysis, electrical energy is converted directly into chemical energy. The product of an electrolytic reaction depends ...
A galvanic cell functions like an electrolytic cell when :
(A) $E_{\text{cell}} = E_{\text{ext}}$
(B) $E_{\text{cell}} > E_{\text{ext}}$
(C) $E_{\text{ext}} > E_{\text{cell}}$
(D) $E_{\text{cell}} = 0$
Based on the data given above, give plausible reason for the variation of conductivity and molar conductivity with concentration.
(a) (i) For a galvanic cell, the following half reactions are given. Decide, which will remain as reduction reaction and which will be reversed to become an oxidation reaction. Give reason for your answer.
(I) $\text{Cr}^{3+} + 3\text{e}^- \rightarrow \text{Cr}(\text{s}); \text{E}^\circ = -\,0\cdot7...
(a) (i) What type of battery is the lead storage battery? Write the anode and the cathode reactions and the overall reaction occurring in a lead storage battery when current is drawn from it.
(ii) Calculate the time to deposit $1.5\text{ g}$ of silver at cathode when a current of $1.5\text{ A}$ was ...
(a) Give reasons :
(i) Mercury cell delivers a constant potential during its life time.
(ii) In the experimental determination of electrolytic conductance, Direct Current (DC) is not used.
OR
(b) Define fuel cell with an example. What advantages do the fuel cells have over primary and secondary batt...
Which of the following cell was used in Apollo space programme ?
(a) Mercury cell
(b) Daniel cell
(c) $\text{H}_2 - \text{O}_2$ Fuel cell
(d) Dry cell
Solutions of two electrolytes X and Y are diluted. Molar conductivity of X increases 25 times whereas that of Y increases 1.5 times. Which one is a stronger electrolyte ?
(a) X
(b) Y
(c) Both X and Y
(d) None of the above
A galvanic cell can behave as an electrolytic cell when :
(a) $E_{\text{cell}} = E_{\text{ext}}$
(b) $E_{\text{cell}} > E_{\text{ext}}$
(c) $E_{\text{cell}} = 0$
(d) $E_{\text{ext}} > E_{\text{cell}}$
(c) When does electrochemical cell behaves like an electrolytic cell?
(a) Answer the following :
(i) Why is the Equilibrium Constant ($K_c$) related to $E^\circ_{\text{cell}}$ and not to $E_{\text{cell}}$ ?
(ii) Two metals 'A' and 'B' have standard electrode potential values of $-0.24\text{ V}$ and $+0.80\text{ V}$ respectively. Which of these will liberate hydrogen...
State Kohlrausch's law of independent migration of ions. With the help of a curve, explain why it is not easy to determine $\Lambda^\circ_{\text{m}}$ for weak electrolytes by extrapolating the concentration – molar conductivity curve, as it is for strong electrolytes.
Which of the following statements is true about a galvanic cell consisting of $\text{Cu}$ and $\text{H}_2$ electrodes ?
(A) Oxidation occurs at copper electrode
(B) Reduction occurs at $\text{H}_2$ electrode
(C) $\text{H}_2$ is cathode and $\text{Cu}$ is anode
(D) $\text{H}_2$ is anode and $\text{Cu...
Define fuel cell. Give two advantages of fuel cell over ordinary cell.
Match the type of cell given in Column I with their use given in Column II.
| Column I | Column II |
|---|---|
| i. Lead storage cell | a. Wall clock |
| ii. Mercury cell | b. Apollo Space Programme |
| iii. Dry cell | c. Wrist watch |
| iv. Fuel cell | d. Inverter |
(A) i-a, ii-b, iii-c, iv-d $\q...
A conductivity cell contains electrodes made up of :
(A) Silver
(B) Copper
(C) Platinum
(D) Zinc
The standard electrode potential for $\text{Sn}^{4+}/\text{Sn}^{2+}$ couple is $+ 0.15 \text{ V}$ and for $\text{Cr}^{3+}/\text{Cr}$ couple is $- 0.73 \text{ V}$. These two couples are connected to make an electrochemical cell. The redox reaction is spontaneous. The cell potential will be :
(A) $+ 0...
The electrical resistance of a column of $0.05 \text{ M NaOH}$ solution of cell constant $50 \text{ cm}^{-1}$ is $4.5 \times 10^3 \text{ ohm}$. Calculate its resistivity, conductivity and molar conductivity.
(a) (i) State Kohlrausch's law of independent migration of ions. Write an expression for the limiting molar conductivity of acetic acid according to Kohlrausch's law. (ii) Calculate the maximum work and $\log K_c$ for the given reaction at $298 \text{ K}$: $\text{Ni (s)} + 2\text{Ag}^+ \text{(aq)} \...
Which of the following is affected by catalyst ?
(a) $\Delta H$
(b) $\Delta G$
(c) $E_a$
(d) $\Delta S$
(a) Define fuel cell and write its two advantages.
OR
(b) Using $E^\circ$ values of X and Y given below, predict which is better for coating the surface of Iron to prevent corrosion and why ?
Given : $E^\circ_{\text{X}^{2+}/\text{X}} = - 2.36 \text{ V}$
$E^\circ_{\text{Y}^{2+}/\text{Y}} = - 0.14 \te...
Kohlrausch gave the following relation for strong electrolyte : $\Lambda = \Lambda_\circ - A\sqrt{C}$. Which of the following equality holds true ? (a) $\Lambda = \Lambda_\circ$ as $C \longrightarrow \sqrt{A}$ (b) $\Lambda = \Lambda_\circ$ as $C \longrightarrow 0$ (c) $\Lambda = \Lambda_\circ$ as $C...
(a) (i) What should be the signs (positive/negative) for $E^\circ_{\text{Cell}}$ and $\Delta G^\circ$ for a spontaneous redox reaction occurring under standard conditions ? (ii) State Faraday's first law of electrolysis. OR (b) Calculate the emf of the following cell at 298 K : $\text{Fe}_{(\text{s}...
Rahul set-up an experiment to find resistance of aqueous $\text{KCl}$ solution for different concentrations at $298\text{ K}$ using a conductivity cell connected to a Wheatstone bridge. He fed the Wheatstone bridge with a.c. power in the audio frequency range $550$ to $5000$ cycles per second. Once ...
In a plot of $\Lambda_m$ against the square root of concentration ($C^{1/2}$) for strong and weak electrolyte, the value of limiting molar conductivity of a weak electrolyte cannot be obtained graphically. Suggest a way to obtain this value. Also state the related law, if any.
Read the passage given below and answer the questions that follow : Oxidation-reduction reactions are commonly known as redox reactions. They involve transfer of electrons from one species to another. In a spontaneous reaction, energy is released which can be used to do useful work. The reaction is ...
OR
(d) The molar conductivity of a $1.5\text{ M}$ solution of an electrolyte is found to be $138.9\text{ S cm}^2\text{ mol}^{-1}$. Calculate the conductivity of this solution.
Answer the following questions (Any two) : (a) Why is alternating current used instead of direct current for measuring resistance of an electrolytic solution ? (b) State Kohlrausch's law of independent migration of ions. (c) Depict the Galvanic cell in which the following reaction takes place : $\te...
(a) Calculate emf and $\Delta G$ for the following cell at $298 ext{ K}$ :
$ ext{Mg(s)} / ext{Mg}^{2+}(0.01 ext{ M}) // ext{Ag}^+(0.001 ext{ M}) / ext{Ag(s)}$
Given : $ ext{E}^\circ_{ ext{Mg}^{2+}/ ext{Mg}} = -2.37 ext{ V}$, $ ext{E}^\circ_{ ext{Ag}^+/ ext{Ag}} = +0.80 ext{ V}$
$[1 ext{ F} = 9650...
(a) Answer the following :
(i) Why is the Equilibrium Constant \((K_c)\) related to \(E^\circ_{\text{cell}}\) and not to \(E_{\text{cell}}\) ?
(ii) Two metals 'A' and 'B' have standard electrode potential values of \(-0.24 \text{ V}\) and \(+0.80 \text{ V}\) respectively. Which of these will liberat...
(a) Calculate emf and $\Delta \text{G}$ for the following cell at $298 \text{ K}$ :
$\text{Mg(s)} / \text{Mg}^{2+}(0.01 \text{ M}) \; // \; \text{Ag}^+(0.001 \text{ M}) / \text{Ag(s)}$
Given : $\text{E}^{\circ}_{\text{Mg}^{2+}/\text{Mg}} = -2.37 \text{ V}$, $\text{E}^{\circ}_{\text{Ag}^+/\text{Ag}} ...
How the conductivity varies on decreasing concentration for both weak and strong electrolytes ?
(A) It increases for weak electrolyte and decreases for strong electrolyte.
(B) It decreases for weak electrolyte and increases for strong electrolyte.
(C) It increases for both weak and strong electrolyt...
32. (a) Calculate emf and $\Delta G$ for the following cell at $298 ext{ K}$ :
$ ext{Mg(s)} / ext{Mg}^{2+}(0.01 ext{ M}) \parallel ext{Ag}^{+}(0.001 ext{ M}) / ext{Ag(s)}$
Given : $E^{\circ}_{ ext{Mg}^{2+}/ ext{Mg}} = -2.37 ext{ V}$, $E^{\circ}_{ ext{Ag}^{+}/ ext{Ag}} = +0.80 ext{ V}$
[$1 ext{ F}...
(b) For the reaction :
$2\text{Ag}Cl(s) + \text{H}_2(\text{g}) (0.4 \text{atm}) \longrightarrow 2\text{Ag}(s) + 2\text{H}^+(0.1 \text{ M}) + 2Cl^-(0.2 \text{ M})$
Calculate emf of the cell at $25 \text{ }^\circ\text{C}$.
Given : $\Delta G^\circ = - 43500 \text{ J mol}^{-1}$
[$\log 10 = 1$, $1 \text{...
(a) Define a fuel cell with an example. Write two advantages of fuel cells.\n(b) Write one difference between primary batteries and secondary batteries.
(a) (i) Define the following terms :
(I) Conductivity
(II) Molar conductivity
(III) Limiting molar conductivity
(ii) Calculate the standard Gibbs energy for the following reaction :
$\text{Zn(s)} + \text{Cu}^{2+}\text{(aq)} \longrightarrow \text{Zn}^{2+}\text{(aq)} + \text{Cu(s)}$
[Given : $E^0_{\te...
The standard electrode potentials of three metals A, B and C are, respectively, $+ 0\cdot 34\text{ V}$, $- 1\cdot 18\text{ V}$ and $- 0\cdot 25\text{ V}$. The correct order of reducing power of these metals is :
(A) $\text{B} > \text{C} > \text{A}$
(B) $\text{A} > \text{B} > \text{C}$
(C) $\text{C} ...
Define conductivity and molar conductivity for a solution of an electrolyte. Why does the conductivity of a solution decrease with decrease in concentration ?
(a) (i) Write the Nernst equation and calculate the emf of the following cell at $298\text{ K}$ :
$ ext{Mg (s)} \mid \text{Mg}^{2+} (0\cdot001\text{ M}) \parallel \text{Cu}^{2+} (0\cdot0001\text{ M}) \mid \text{Cu (s)}$
Given : $E^\circ_{\text{Mg}^{2+}/\text{Mg}} = -2\cdot36\text{ V}$, $E^\circ_{\te...
OR
(b) (i) The cell in which the following reaction occurs :
$2\text{Fe}^{3+} (\text{aq}) + 2\text{I}^- (\text{aq}) \longrightarrow 2\text{Fe}^{2+} (\text{aq}) + \text{I}_2 (\text{s})$
has $E^\circ_{(\text{cell})} = 0\cdot24\text{ V}$ at $298\text{ K}$. Calculate $\Delta_r G^\circ$ and $\log K_C$ of...
State Kohlrausch's law of independent migration of ions. With the help of a curve, explain why it is not easy to determine $\land^{\circ}_{ ext{m}}$ for weak electrolytes by extrapolating the concentration $-$ molar conductivity curve, as it is for strong electrolytes.
(a) (i) Calculate the electrode potential of a half-cell for zinc electrode dipping in $0.01~\text{M }\text{ZnSO}_4$ solution at $25^\circ\text{C}$.
Given : $E^\circ_{\text{Zn}^{2+}/\text{Zn}} = -0.76~\text{V}$
$[\log 10 = 1]$
(ii) Write anode, cathode and overall reaction involved in dry cell.
(iii...
(a) (i) Calculate the electrode potential of a half-cell for zinc electrode dipping in $0.01 \text{ M } \text{ ZnSO}_4$ solution at $25^\circ\text{C}$.
Given : $\text{E}^{\circ}_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \text{ V}$
$[\log 10 = 1]$
(ii) Write anode, cathode and overall reaction involved in d...
(b) (i) The conductivity of $0.001 \text{ M}$ solution of acetic acid is $3.905 \times 10^{-5} \text{ S cm}^{-1}$. Calculate its molar conductivity and degree of dissociation ($\alpha$).
Given : $\lambda^\circ_{\text{CH}_3\text{COO}^-} = 40.9 \text{ S cm}^2 \text{ mol}^{-1}$
$\lambda^\circ_{\text{H}...
(ii) Write anode, cathode and overall reaction involved in dry cell.
(iii) Equilibrium constant ($K_c$) is related to $E^0_{cell}$, but not to $E_{cell}$. Why?
OR
(b) (i) The conductivity of $0\cdot001\text{ M}$ solution of acetic acid is $3\cdot905 \times 10^{-5}\text{ S cm}^{-1}$. Calculate its mo...
Consider the following cell at $298\text{ K}$ :
$ ext{Mg (s)} \mid \text{Mg}^{2+} \, (1\cdot 0\text{ M}) \parallel \text{Cu}^{2+} \, (1\cdot 0\text{ M}) \mid \text{Cu (s)}$
How can we increase the emf of the cell using the same substances ?
(A) By decreasing only the $[\text{Mg}^{2+}]$ to $0\cdot 1\...
33. (a) (i) Calculate $E_{ ext{cell}}^{0}$ for the following reaction which is at equilibrium :
$ ext{Cu (s)} + 2 ext{Ag}^{+} ext{(aq)}
ightleftharpoons ext{Cu}^{2+} ext{(aq)} + 2 ext{Ag (s)}$
Equilibrium constant ($K_c$) for the cell is $10^{15}$.
[Given : $\log 10 = 1$]
(ii) Write anode, catho...
Consider the following cell at $298 \text{ K}$ :
$\text{Mg (s)} \mid \text{Mg}^{2+} (1.0 \text{ M}) \parallel \text{Cu}^{2+} (1.0 \text{ M}) \mid \text{Cu (s)}$
How can we increase the emf of the cell using the same substances ?
(A) By decreasing only the $[\text{Mg}^{2+}]$ to $0.1 \text{ M}$
(B) By...
(a) (i) Calculate $E^{\circ}_{\text{cell}}$ for the following reaction which is at equilibrium :
$\text{Cu (s)} + 2\text{Ag}^+ \text{ (aq)} \rightleftharpoons \text{Cu}^{2+} \text{ (aq)} + 2\text{Ag (s)}$
Equilibrium constant ($K_c$) for the cell is $10^{15}$.
[Given : $\log 10 = 1$]
(ii) Write anod...
Consider the following cell at $298 \text{ K}$ :
$\text{Mg (s)} \mid \text{Mg}^{2+} (1\cdot0 \text{ M}) \parallel \text{Cu}^{2+} (1\cdot0 \text{ M}) \mid \text{Cu (s)}$
How can we increase the emf of the cell using the same substances ?
(A) By decreasing only the $[\text{Mg}^{2+}]$ to $0\cdot1 \text...
(a) (i) Calculate $E_{ ext{cell}}^{\circ}$ for the following reaction which is at equilibrium :
$ ext{Cu (s)} + 2 ext{Ag}^+ ext{(aq)}
ightleftharpoons ext{Cu}^{2+} ext{(aq)} + 2 ext{Ag (s)}$
Equilibrium constant ($K_c$) for the cell is $10^{15}$.
[Given : $\log 10 = 1$]
(ii) Write anode, cathod...
(a) Name the cell which was used in the Apollo space programme for providing electrical power.
(b) Define limiting molar conductivity.
(a) Name any two materials other than hydrogen that can be used as fuel in fuel cells.
(b) Define molar conductivity.
Which of the following statements is true about a galvanic cell consisting of $ ext{Cu}$ and $ ext{H}_2$ electrodes ?
(A) Oxidation occurs at copper electrode
(B) Reduction occurs at $ ext{H}_2$ electrode
(C) $ ext{H}_2$ is cathode and $ ext{Cu}$ is anode
(D) $ ext{H}_2$ is anode and $ ext{Cu}$ is c...
Write the reactions taking place at anode and cathode in a dry cell.
The resistance and conductivity of a conductivity cell containing $0\cdot1\text{ mol L}^{-1}\text{ KCl}$ solution are $100\text{ ohms}$ and $1\cdot29 \times 10^{-2}\text{ S cm}^{-1}$, respectively. If the resistance of the same cell filled with $0\cdot02\text{ mol L}^{-1}\text{ KCl}$ solution is $52...
The electrical resistance of a column of $0\cdot05\text{ M KOH}$ solution of area $0\cdot5\text{ cm}^2$ and length $50\text{ cm}$ is $2\cdot5 \times 10^4\text{ ohm}$. Calculate its molar conductivity.
Write the reactions taking place at anode and cathode in a lead storage battery, when it is in use.
Conductivity of $2.5 \times 10^{-4}\text{ M}$ methanoic acid solution is $5.25 \times 10^{-5}\text{ S cm}^{-1}$.
(a) Calculate its molar conductivity.
(b) Calculate its degree of dissociation.
[Given : $\lambda^0_{(\text{H}^+)} = 349.5\text{ S cm}^2\text{ mol}^{-1}$ and $\lambda^0_{(\text{HCOO}^-)} ...
Write the Nernst equation for the following:
I. $ ext{Ni (s)} + ext{Cu}^{2+} ext{ (aq)}
ightarrow ext{Ni}^{2+} ext{ (aq)} + ext{Cu (s)}$
II. $ ext{Al (s)} + ext{FeSO}_4 ext{ (aq)}
ightarrow ext{Al}_2( ext{SO}_4)_3 ext{ (aq)} + ext{Fe (s)}$
III. $ ext{Mg (s)}/ ext{Mg}^{2+} ext{ (aq)}// ...
Refer to the table given below and draw the molar conductivity vs. concentration curve for solution A and B.
Solution | Red LED | Green LED
---|---|---
A | bright | dim
B | dim | off
(For Visually Challenged students)
Conductivity of Aqueous Solutions
Conductivity meter is a device which is used...
Which of the following cells has a constant voltage throughout its life ?\n(A) Dry cell\n(B) Daniell cell\n(C) Electrolytic cell\n(D) Mercury cell
State Kohlrausch's Law of independent migration of ions. Solutions of two electrolytes 'A' and 'B' are diluted. The limiting molar conductivity of 'B' increases $2\cdot5$ times while that of 'A' increases $25$ times. Which of the two is a strong electrolyte ? Justify your answer.
(a) (i) Calculate emf of the following cell at $25^\circ ext{C}$ :
$\text{Sn} \mid \text{Sn}^{2+} (0\cdot001\text{ M}) \parallel \text{H}^+ (0\cdot01\text{ M}) \mid \text{H}_2(\text{g}) (1\text{ bar}), \text{Pt}(\text{s})$
$E^\circ_{\text{Sn}^{2+}/\text{Sn}} = -0\cdot14\text{ V}, \ E^\circ_{\text{H}...
Kohlrausch gave the following relation for strong electrolytes at low concentration :
$$\Lambda_m = \Lambda_m^0 - A\sqrt{C}$$
Which of the following equality holds true ?
(A) $\Lambda_m = \Lambda_m^0 \text{ as } C \rightarrow \sqrt{A}$
(B) $\Lambda_m = \Lambda_m^0 \text{ as } C \rightarrow 0$
(C) $\...
(a) Why does the cell potential of mercury cell remains constant throughout its life ?
(b) Calculate the degree of dissociation $(\alpha)$ of $ ext{CH}_3 ext{COOH}$ if $\Lambda_ ext{m}$ and $\Lambda_ ext{m}^0$ of $ ext{CH}_3 ext{COOH}$ are $50 ext{ S cm}^2 ext{ mol}^{-1}$ and $400 ext{ S cm}^2 ext{ ...
Using the $E^0$ values of P and Q, predict which one is better for coating the surface of iron [$E^0_{( ext{Fe}^{2+}/ ext{Fe})} = -0.44 ext{ V}$] to prevent corrosion and why ?
$E^0_{( ext{P}^{2+}/ ext{P})} = -2.37 ext{ V}$, $E^0_{( ext{Q}^{2+}/ ext{Q})} = -0.14 ext{ V}$
In an electrochemical cell, the following reaction takes place :
$2\text{Cu}^+(\text{aq}) + \text{Zn (s)} \rightarrow 2\text{Cu (s)} + \text{Zn}^{2+}(\text{aq})$
$E^\circ_{\text{cell}} = 1\cdot28\text{ V}$
As the reaction progresses, what will happen to the overall voltage of the cell ?
(A) Voltage ...
Calculate the cell voltage of the voltaic cell which is set up by joining following half-cells at $25^\circ\text{C}$ :
$\text{Al/Al}^{3+} (0.001\text{ M})$ and $\text{Ni/Ni}^{2+} (0.1\text{ M})$
Given : $\text{E}^\circ_{\text{Ni}^{2+}/\text{Ni}} = - 0\cdot25\text{ V}$, $\text{E}^\circ_{\text{Al}^{3+...
In an electrochemical cell, the following reaction takes place :
$2\text{Ag}^+ \text{ (aq)} + \text{Mg (s)} \rightarrow 2\text{Ag (s)} + \text{Mg}^{2+} \text{ (aq)}$
$E^\circ_{\text{cell}} = 2\cdot96 \text{ V}$
As the reaction progresses, what will happen to the overall voltage of the cell ?
(A) Vol...
Calculate the cell voltage of the voltaic cell which is set up by joining the following half-cells at $25^\circ\text{C}$ :
$\text{Al} / \text{Al}^{3+} (0.001\text{ M})$ and $\text{Ni} / \text{Ni}^{2+} (0.001\text{ M})$
Given : $\text{E}^\circ_{\text{Ni}^{2+}/\text{Ni}} = -0.25\text{ V}$
$\text{E}^\c...
In an electrochemical cell, the following reaction takes place :
$2\text{Cu}^{+}(\text{aq}) + \text{Zn}(\text{s}) \rightarrow 2\text{Cu}(\text{s}) + \text{Zn}^{2+}(\text{aq})$
$E^{\circ}_{\text{cell}} = 1\cdot 28\text{ V}$
As the reaction progresses, what will happen to the overall voltage of the ce...
Calculate the cell voltage of the voltaic cell which is set up by joining the following half-cells at $25^\circ\text{C}$.
$\text{Al} / \text{Al}^{3+} (0\cdot002 \text{ M})$ and $\text{Ni} / \text{Ni}^{2+} (0\cdot002 \text{ M})$
Given : $\text{E}^\circ_{\text{Ni}^{2+}/\text{Ni}} = -\,0\cdot25 \text{ ...
(b) (i) State Kohlrausch's law. Give any two applications of it.
Match the type of cell given in Column I with their use given in Column II.\n\nColumn I\n\ni. Lead storage cell\nii. Mercury cell\niii. Dry cell\niv. Fuel cell\n\nColumn II\n\na. Wall clock\nb. Apollo Space Programme\nc. Wrist watch\nd. Inverter\n\n(A) i-a, ii-b, iii-c, iv-d\n(B) i-d, ii-c, iii-a, i...
OR
(b) (i) State Kohlrausch's law. Give any two applications of it.
Which of the following cell converts the energy of combustion of fuel into electrical energy ?
(A) Mercury cell
(B) Fuel cell
(C) Dry cell
(D) Lead storage cell
Give reasons for the following :
(a) The $\text{pH}$ of aqueous $\text{NaCl}$ increases when it is electrolysed.
(b) Unlike dry cell, mercury cell has a constant cell potential through its lifetime.
(c) Conductivity of solution decreases with dilution.
(a) (i) Calculate $E_{\text{cell}}$ of a galvanic cell in which the following reaction takes place at $25^\circ\text{C}$ :
$\text{Zn(s)} + \text{Pb}^{2+}(0\cdot02\text{ M}) \longrightarrow \text{Zn}^{2+}(0\cdot1\text{ M}) + \text{Pb(s)}$
[Given : $E^\circ_{\text{Zn}^{2+}/\text{Zn}} = -\,0\cdot76\tex...
A galvanic cell can behave like an electrolytic cell when
(A) $E_{ ext{cell}} = E_{ ext{ext}}$
(B) $E_{ ext{ext}} > E_{ ext{cell}}$
(C) $E_{ ext{cell}} > E_{ ext{ext}}$
(D) $E_{ ext{cell}} = 0$
Give reasons for the following :\n(a) The $\text{pH}$ of aqueous $\text{NaCl}$ increases when it is electrolysed.\n(b) Unlike dry cell, mercury cell has a constant cell potential through its lifetime.\n(c) Conductivity of solution decreases with dilution.
(a) (i) Calculate $E_{ ext{cell}}$ of a galvanic cell in which the following reaction takes place at $25^{\circ}\text{C}$ :
$\text{Zn(s)} + \text{Pb}^{2+}(0\cdot02\text{ M}) \longrightarrow \text{Zn}^{2+}(0\cdot1\text{ M}) + \text{Pb(s)}$
[Given : $E^{\circ}_{\text{Zn}^{2+}/\text{Zn}} = - 0\cdot76\t...
Give reasons for the following :
(a) The pH of aqueous $ ext{NaCl}$ increases when it is electrolysed.
(b) Unlike dry cell, mercury cell has a constant cell potential through its lifetime.
(c) Conductivity of solution decreases with dilution.
(a) (i) Calculate $E_{ ext{cell}}$ of a galvanic cell in which the following reaction takes place at $25^{\circ}\text{C}$ :
$\text{Zn(s)} + \text{Pb}^{2+}(0.02 \text{ M}) \longrightarrow \text{Zn}^{2+}(0.1 \text{ M}) + \text{Pb(s)}$
[Given : $E_{\text{Zn}^{2+}/\text{Zn}}^{\circ} = - 0.76 \text{ V}$,...
Answer the following questions :
The conductivity of $0\cdot20 ext{ M}$ solution of $ ext{KCl}$ is $2\cdot48 imes 10^{-2} ext{ S cm}^{-1}$. Calculate its molar conductivity and degree of dissociation $(\alpha)$.
$[\text{Given} : \lambda^\circ_{( ext{K}^+)} = 73\cdot5 ext{ S cm}^2 ext{ mol}^{-1}$
$\...
What type of cell is mercury cell ? Why is it more advantageous than dry cell ?
Kohlrausch gave the following relation for strong electrolytes :
$\Lambda_{\text{m}} = \Lambda_{\text{m}}^{\circ} - \text{A}\sqrt{C}$
Which of the following equality holds true ?
(A) $\Lambda_{\text{m}} = \Lambda_{\text{m}}^{\circ}$ as $C \longrightarrow 1$
(B) $\Lambda_{\text{m}} = \Lambda_{\text{m...
(b) Answer the following questions :
(i) The conductivity of $0\cdot20 ext{ M}$ solution of $ ext{KCl}$ is $2\cdot48 imes 10^{-2} ext{ S cm}^{-1}$. Calculate its molar conductivity and degree of dissociation ($\alpha$).
[Given : $\lambda^{\circ}_{( ext{K}^+)} = 73\cdot5 ext{ S cm}^2 ext{ mol}^{-1}$...
(ii) Calculate $\Delta_r G^{\circ}$ of the following cell :
$\text{Mg}(s) + \text{Cu}^{2+}(aq) \longrightarrow \text{Mg}^{2+}(aq) + \text{Cu}(s)$
$[\text{Given} : E^{\circ}_{\text{Mg}^{2+}/\text{Mg}} = - 2.37~\text{V}, \quad E^{\circ}_{\text{Cu}^{2+}/\text{Cu}} = + 0.34~\text{V}$
$1\text{ F} = 96500...
A conductivity cell usually consists of two :
(A) Copper electrodes (B) Platinum electrodes
(C) Zinc electrodes (D) Iron electrodes
(b) Answer the following questions :
(i) The conductivity of $0.20\text{ M}$ solution of $\text{KCl}$ is $2.48 \times 10^{-2}\text{ S cm}^{-1}$. Calculate its molar conductivity and degree of dissociation $(\alpha)$.
[Given : $\lambda^\circ_{(\text{K}^+)} = 73.5\text{ S cm}^2\text{ mol}^{-1}$
$\l...
The standard electrode potential of 'A', 'B' and 'C' are $+ 0.68\text{ V}$, $- 2.54\text{ V}$ and $- 0.50\text{ V}$ respectively. The order of their reducing power is :
(A) $ ext{A} > ext{B} > ext{C}$
(B) $ ext{A} > ext{C} > ext{B}$
(C) $ ext{B} > ext{C} > ext{A}$
(D) $ ext{C} > ext{B} > ext...
The standard electrode potential of 'A', 'B' and 'C' are $+ 0.68\text{ V}$, $- 2.54\text{ V}$ and $- 0.50\text{ V}$ respectively. The order of their reducing power is :
(A) $\text{A} > \text{B} > \text{C}$
(B) $\text{A} > \text{C} > \text{B}$
(C) $\text{B} > \text{C} > \text{A}$
(D) $\text{C} > \tex...
The standard electrode potentials of 'P', 'Q' and 'R' are $-0.50\text{ V}$, $+0.68\text{ V}$ and $-2.54\text{ V}$ respectively. The order of their reducing power is :
(A) $\text{R} > \text{P} > \text{Q}$
(B) $\text{Q} > \text{P} > \text{R}$
(C) $\text{Q} > \text{R} > \text{P}$
(D) $\text{P} < \text{...
Assertion (A): For strong electrolytes, there is a slow increase in molar conductivity with dilution and can be represented by the equation
$\Lambda_m^\circ = \Lambda_m - A \ c^{1/2}$
Reason (R): The value of the constant ‘A’ for $\text{NaCl}$, $\text{CaCl}_2$, and $\text{MgSO}_4$ in a given solvent...
The equilibrium constant of cell reaction :
$\text{Sn}^{4+}(\text{aq}) + \text{Al}(\text{s}) \rightarrow \text{Al}^{3+} + \text{Sn}^{2+} (\text{aq})$ is $4.617 \times 10^{184}$, at 25°C
a. Calculate the standard emf of the cell.
(Given: $\log 4.617 \times 10^{184} = 184.6644$)
b. What will be the $\...
Which of the following cell was used in Apollo space programme ?
(A) Dry cell
(B) Ni-Cd cell
(C) $\text{H}_2 - \text{O}_2$ fuel cell
(D) Mercury cell
Consider the following standard electrode potential values :
$\text{Fe}^{3+} + 1\text{e}^- \rightarrow \text{Fe}^{2+}; \text{E}^{\circ} = + 0\cdot77 \text{ V}$
$\text{MnO}_4^- + 8\text{H}^+ + 5\text{e}^- \rightarrow \text{Mn}^{2+} + 4\text{H}_2\text{O}; \text{E}^{\circ} = + 1\cdot51 \text{ V}$
Wh...
Conductivity of $2 \times 10^{-3} \text{ M}$ methanoic acid is $8 \times 10^{-5} \text{ S cm}^{-1}$. Calculate its molar conductivity and degree of dissociation if $\Lambda^0_m$ for methanoic acid is $404 \text{ S cm}^2 \text{ mol}^{-1}$.
Oxidation-reduction reactions are commonly known as redox reactions. In galvanic cell, the chemical energy of a spontaneous redox reaction is converted into electrical energy, whereas in an electrolytic cell, electrical energy is used to carry out a non-spontaneous redox reaction. The standard elect...
(b) When does a galvanic cell behave like an electrolytic cell ?
(c) (i) Define the following terms :
(1) Redox reaction
(2) Galvanic cell
(c) (ii) Write cell reaction and Nernst equation for the following cell at $25^\circ\text{C}$ :
$\text{Ni (s)} | \text{Ni}^{2+} \text{(aq)} || \text{Ag}^+ \text{(aq)} | \text{Ag (s)}$
The conductivity of $0\cdot2\text{ M}$ solution of $\text{KCl}$ is $2\cdot48 \times 10^{-2}\text{ S cm}^{-1}$. Calculate its molar conductivity and degree of dissociation $(\alpha)$.
Given :
$\lambda^0_{\text{K}^+} = 73\cdot5\text{ S cm}^2\text{ mol}^{-1}$
$\lambda^0_{\text{Cl}^-} = 76\cdot5\text{ S...
(b) (i) Calculate the $\Delta_{r}G^{o}$ and $\log K_{c}$ for the following cell reaction :
Fe (s) + Ag^{+} (aq) $\rightleftharpoons$ Fe^{2+} (aq) + Ag (s)
Given : E^{o}_{Fe^{2+}/Fe} = -0.44 V, E^{o}_{Ag^{+}/Ag} = +0.80 V,
1 F = 96500 C mol^{-1}
(ii) Write any two advantages of the fuel cells over ...
Which of the following is a secondary cell ?
(A) Dry cell
(B) Lead storage cell
(C) Mercury cell
(D) Daniell cell
The conductivity of $0\cdot2$ M solution of KCl is $2\cdot48 \times 10^{-2}$ $\text{S cm}^{-1}$. Calculate its molar conductivity and degree of dissociation ($\alpha$). Given : $\lambda^{0}_{K^{+}} = 73\cdot5$ $\text{S cm}^{2} \text{mol}^{-1}$ $\lambda^{0}_{Cl^{-}} = 76\cdot5$ $\text{S cm}^{2} \text...
OR (b) (i) Calculate the $\Delta_r\text{G}^o$ and $\log \text{K}_c$ for the following cell reaction : $\text{Fe (s) + Ag}^+ \text{(aq)} \rightleftharpoons \text{Fe}^{2+} \text{(aq) + Ag (s)}$ Given : $\text{E}^o_{\text{Fe}^{2+}/\text{Fe}} = -0.44 \text{ V, E}^o_{\text{Ag}^+/\text{Ag}} = +0.80 \text{...
Which of the following cells is used in hearing aids ?
(A) Dry cell
(B) Mercury cell
(C) Nickel-cadmium cell
(D) Fuel cell
The conductivity of 0.2 M solution of KCl is $2.48 \times 10^{-2} \text{ S cm}^{-1}$. Calculate its molar conductivity and degree of dissociation ($\alpha$).
Given :
$\lambda^{0}_{K^{+}} = 73.5 \text{ S cm}^{2} \text{ mol}^{-1}$
$\lambda^{0}_{Cl^{-}} = 76.5 \text{ S cm}^{2} \text{ mol}^{-1}$
(ii) Write any two advantages of the fuel cells over primary and secondary batteries ?
The electrical resistance of a column of 0.05 M KOH solution of cell constant 60 cm$^{-1}$ is 5.4 $\times$ 10$^{3}$ ohm. Calculate its resistivity, conductivity and molar conductivity.
State Kohlrausch's law of independent migration of ions. Molar conductivity at infinite dilution for $\text{NH}_4\text{Cl}$, $\text{NaOH}$ and $\text{NaCl}$ solution at $298 \text{ K}$ are $110$, $100$ and $105 \text{ S cm}^2 \text{ mol}^{-1}$ respectively. Calculate the molar conductivity of $\text...
Calculate $\Delta G^{\circ}$ of the following cell at $25^{\circ}\text{C}$ :
$\text{Zn (s) | Zn}^{2+}\text{(aq) || Cu}^{2+}\text{(aq) | Cu (s)}$
Given : $E^{\circ}_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \text{ V}$
$E^{\circ}_{\text{Cu}^{2+}/\text{Cu}} = +0.34 \text{ V}$
$1 \text{ F} = 96500 \text{ C mol...
The standard electrode potential for $\text{Ni}^{2+}/\text{Ni}$ couple is $-0.25 \text{ V}$ and for $\text{Ag}^{+}/\text{Ag}$ couple is $0.80 \text{ V}$. These two couples are connected to make an electrochemical cell. The redox reaction is spontaneous. The cell potential will be :
(A) $+1.05 \text{...
(b) (i) State Kohlrausch's law of independent migration of ions. Molar conductivity at infinite dilution for $\text{NH}_4\text{Cl}$, $\text{NaOH}$ and $\text{NaCl}$ solution at $298 \text{ K}$ are $110$, $100$ and $105 \text{ S cm}^2 \text{ mol}^{-1}$ respectively. Calculate the molar conductivity o...
(ii) Calulate $\Delta G^{\circ}$ of the following cell at $25^{\circ}\text{C}$ : $\text{Zn (s)} | \text{Zn}^{2+}\text{(aq)} || \text{Cu}^{2+}\text{(aq)} | \text{Cu (s)}$ Given : $E^{\circ}_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \text{ V}$ $E^{\circ}_{\text{Cu}^{2+}/\text{Cu}} = +0.34 \text{ V}$ $1 \text...
Define conductivity and molar conductivity for the solution of an electrolyte. Discuss their variation with concentration.
(a) (i) Depict the galvanic cell in which the reaction $\text{Zn (s)} + 2\text{Ag}^+ \text{(aq)} \rightarrow \text{Zn}^{2+} \text{(aq)} + 2\text{Ag (s)}$ takes place. Further show : (1) which of the electrodes is negatively charged ? (2) the carriers of the current in the cell. (ii) Define fuel cell...
OR (b) (i) State the following : (1) Kohlrausch law (2) Faraday's first law of electrolysis (ii) Define the following : (1) Corrosion (2) Primary batteries and secondary batteries. Give one example in each case.
(a) (i) State Kohlrausch's law of independent migration of ions. Write an expression for the molar conductivity of acetic acid at infinite dilution according to Kohlrausch's law.
(ii) Calculate the maximum work and $\log \text{K}_\text{c}$ for the given reaction at $298 \text{ K}$ :
$\text{Ni (s)} +...
$\Delta G$ and $E^{\circ}_{\text{cell}}$ for a spontaneous reaction will be :
(a) positive, negative
(b) negative, negative
(c) negative, positive
(d) positive, positive
(a) Can we construct an electrochemical cell with two half-cells composed of $\text{ZnSO}_4$ solution and zinc electrodes? Explain your answer.
(b) Calculate the $\lambda^0_m$ for $\text{Cl}^-$ ion from the data given below:
$\lambda^0_m \text{MgCl}_2 = 258.6 \text{ S cm}^2 \text{mol}^{-1}$ and $\la...
The lead-acid battery represents the oldest rechargeable battery technology. Lead acid batteries can be found in a wide variety of applications including small-scale power storage such as UPS systems, ignition power sources for automobiles, along with large, grid-scale power systems. The spongy lead...
Attempt any five of the following:
(a) Which of the following ions will have a magnetic moment value of $1.73$ BM.
$\text{Sc}^{3+}, \text{Ti}^{3+}, \text{Ti}^{2+}, \text{Cu}^{2+}, \text{Zn}^{2+}$
(b) In order to protect iron from corrosion, which one will you prefer as a sacrificial electrode, Ni o...
Which of the following solutions of $\text{KCl}$ will have the highest value of molar conductivity ?
(a) 0.01 M
(b) 1 M
(c) 0.5 M
(d) 0.1 M
(a) Conductivity of $2 \times 10^{-3}$ M methanoic acid is $8 \times 10^{-5}$ S $\text{cm}^{-1}$. Calculate its molar conductivity and degree of dissociation if $\wedge^{\circ}_{m}$ for methanoic acid is $404$ S $\text{cm}^{2}\text{mol}^{-1}$. (b) Calculate the $\Delta_{r}G^{\circ}$ and $\log K_{c}$...
Assertion (A) : Molar conductivity decreases with increase in concentration.
Reason (R) : When concentration approaches zero, the molar conductivity is known as limiting molar conductivity.
(b) Define fuel cell with an example. What advantages do the fuel cells have over primary and secondary batteries ?
Which of the following cells has a constant voltage throughout its life?
(a) Dry cell
(b) Electrolytic cell
(c) Mercury cell
(d) Daniell cell
(a) Write anode, cathode and overall reaction of lead storage battery. OR (b) Define fuel cell with an example. Write two advantages of fuel cell compared to other ordinary cells.
(a) (i) Calculate $E^0_{\text{cell}}$ for the following reaction at $298 \text{ K} : 2\text{Al (s)} + 3\text{Cu}^{2+} (0.01 \text{ M}) \longrightarrow 2\text{Al}^{3+} (0.01 \text{ M}) + 3\text{Cu (s)}$. Given : $E_{\text{cell}} = 1.98 \text{ V}$, $\log 10 = 1$. (ii) Using the $E^0$ values of A and B...
OR (b) (i) The conductivity of $0.001 \text{ M}$ solution of $\text{CH}_3\text{COOH}$ is $3.905 \times 10^{-5} \text{ S cm}^{-1}$. Calculate its degree of dissociation ($\alpha$). Given : $\lambda^0_{\text{CH}_3\text{COO}^-} = 40.9 \text{ S cm}^2 \text{ mol}^{-1}$, $\lambda^0_{\text{H}^+} = 349.6 \t...
Kohlrausch gave the following relation for strong electrolyte :
$\Lambda = \Lambda_\circ - A\sqrt{\text{C}}$
Which of the following equality holds true ?
(a) $\Lambda = \Lambda_\circ$ as $\text{C} \longrightarrow \sqrt{\text{A}}$
(b) $\Lambda = \Lambda_\circ$ as $\text{C} \longrightarrow 0$
(c) $\La...
(a) Calculate the emf of the following cell at $25^\circ\text{C}$:
$\text{Zn (s) | Zn}^{2+} (0.1 \text{ M) || H}^+ (0.01 \text{ M) | H}_2 \text{ (g) (1 bar), Pt (s)}$
[Given: $E^\circ_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \text{ V}, E^\circ_{\text{H}^+/\text{H}_2} = 0.00 \text{ V}, \log 10 = 1]$
(b) St...
(a) Calculate the emf of the following cell at $25^\circ\text{C}$ : $\text{Zn (s) | Zn}^{2+} (0.1 \text{ M) || H}^+ (0.01 \text{ M) | H}_2 \text{ (g) (1 bar), Pt (s)}$ [Given : $\text{E}^\circ_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \text{ V, E}^\circ_{\text{H}^+/\text{H}_2} = 0.00 \text{ V, log 10} = 1$...
The cathode reaction during the charging of a lead storage battery leads to the :
(a) formation of $\text{PbSO}_4$
(b) reduction of $\text{Pb}^{2+}$ to $\text{Pb}^{4+}$
(c) formation of $\text{PbO}_2$ and $\text{Pb}$
(d) deposition of $\text{Pb}$ at the anode
(a) Define fuel cell and write its two advantages.
(b) Using $E^\circ$ values of X and Y given below, predict which is better for coating the surface of Iron to prevent corrosion and why ?
Given : $E^\circ_{ ext{X}^{2+}/ ext{X}} = -2.36 \text{ V}$
$E^\circ_{ ext{Y}^{2+}/ ext{Y}} = -0.14 \text{ V}$
$E^\circ_{ ext{Fe}^{2+}/ ext{Fe}} = -0.44 \text{ V}$
(a) Calculate the emf of the following cell at $25^\circ\text{C}$ : $\text{Zn (s) } | \text{ Zn}^{2+} (0.1 \text{ M) } || \text{ H}^+ (0.01 \text{ M) } | \text{ H}_2 \text{ (g) } (1 \text{ bar), Pt (s)}$ [Given : $\text{E}^\circ_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \text{ V, E}^\circ_{\text{H}^+/\text...
(a) (i) Calculate the emf of the following cell at 298 K : Al (s) | Al$^{3+}$ (0.001 M) || Ni$^{2+}$ (0.1 M) | Ni (s) [Given : E$^{\circ}_{Al^{3+} / Al} = -1.66 V, E^{\circ}_{Ni^{2+} / Ni} = -0.25 V, \log 10 = 1] (ii) With the help of a graph explain why it is not possible to determine $\Lambda^{\ci...
(a) (i) Calculate the emf of the following cell at $298\text{ K}$: $\text{Al (s) | Al}^{3+} (0.001\text{ M) || Ni}^{2+} (0.1\text{ M) | Ni (s)}$. [Given: $\text{E}^{\circ}_{\text{Al}^{3+}/\text{Al}} = -1.66\text{ V, E}^{\circ}_{\text{Ni}^{2+}/\text{Ni}} = -0.25\text{ V, log 10} = 1$] (ii) With the h...
Assertion (A) : Limiting molar conductivity ($\Lambda_m^\circ$) is obtained by the extrapolation of the $\Lambda_m$ versus $C^{1/2}$ curve of strong electrolyte.
Reason (R) : $\Lambda_m^\circ$ for weak electrolytes is obtained by using Kohlrausch's law.
(a) (i) Calculate the emf of the following cell at $298 \text{ K}$ :
$\text{Al (s) | Al}^{3+} (0.001 \text{ M) || Ni}^{2+} (0.1 \text{ M) | Ni (s)}$
$\text{[Given : E}^{\circ}_{\text{Al}^{3+}/\text{Al}} = -1.66 \text{ V, E}^{\circ}_{\text{Ni}^{2+}/\text{Ni}} = -0.25 \text{ V, log } 10 = 1]$
(ii) Wit...
OR
(b) (i) The molar conductivities of $\text{NH}_{4}^{+}$ and $\text{Cl}^{-}$ ion are $73.8 \text{ S cm}^{2} \text{ mol}^{-1}$ and $76.2 \text{ S cm}^{2} \text{ mol}^{-1}$ respectively. The conductivity of $0.1 \text{ M NH}_{4}\text{Cl}$ is $1.29 \times 10^{-2} \text{ S cm}^{-1}$. Calculate its mol...
Rahul set-up an experiment to find resistance of aqueous $\text{KCl}$ solution for different concentrations at 298 K using a conductivity cell connected to a Wheatstone bridge. He fed the Wheatstone bridge with a.c. power in the audio frequency range 550 to 5000 cycles per second. Once the resistanc...
Consider the following standard electrode potential values :
$\text{Fe}^{3+}_{(aq)} + \text{e}^- \rightarrow \text{Fe}^{2+}_{(aq)}$ $\text{E}^\circ = + 0.77 \text{ V}$
$\text{MnO}_4^-_{(aq)} + 8\text{H}^+ + 5\text{e}^- \rightarrow \text{Mn}^{2+}_{(aq)} + 4 \text{H}_2\text{O}_{(l)}$ $\text{E}^\circ =...
Consider the following standard electrode potential values :
$\text{Sn}^{2+}_{(aq)} + 2e^- \to \text{Sn}_{(s)} \quad E^\circ = -0.14 \text{ V}$
$\text{Fe}^{3+}_{(aq)} + e^- \to \text{Fe}^{2+}_{(aq)} \quad E^\circ = +0.77 \text{ V}$
What is the cell reaction and potential for the spontaneous reaction...
The unit of molar conductivity is
(a) $\text{S cm}^{-2} \text{mol}^{-1}$
(b) $\text{S cm}^2 \text{mol}^{-1}$
(c) $\text{S}^{-1} \text{cm}^2 \text{mol}^{-1}$
(d) $\text{S cm}^2 \text{mol}$
(a) (i) A cell and its emf is given below :
$\text{Pt (s) | H}_2\text{ (g, 1 bar) | H}^+\text{ (aq, 1M) || Cu}^{2+}\text{ (aq, 1M) | Cu (s)}$
$ ext{emf of the cell} = + 0.34\text{ V}$.
Write the reduction half-reaction at cathode.
(ii) How is standard Gibbs energy for a reaction related to equilibri...
OR (b) (i) State Kohlrausch's law of independent migration of ions.
(ii) How much electricity in terms of Faraday is required to produce $40\text{ g}$ of $\text{Al}$ from molten $\text{Al}_2\text{O}_3$?
(Given : atomic mass of $\text{Al} = 27\text{ u}$)
(iii) Calculate $\log K_c$ for the following r...
(a) Why is mercury cell better than dry cell?
(b) Why is fuel cell preferred over other cells?
(a) (i) A cell and its emf is given below :
$ ext{Pt (s)} \mid ext{H}_2 ext{(g, 1 bar)} \mid ext{H}^+ ext{(aq, 1 M)} \parallel ext{Cu}^{2+} ext{(aq, 1M)} \mid ext{Cu (s)}$
emf of the cell $= + 0.34 ext{ V}$.
Write the reduction half-reaction at cathode.
(ii) How is standard Gibbs energy for ...
OR
(b) (i) State Kohlrausch's law of independent migration of ions.
(ii) How much electricity in terms of Faraday is required to produce $40 ext{ g}$ of $ ext{Al}$ from molten $ ext{Al}_2 ext{O}_3$ ?
(Given : atomic mass of $ ext{Al} = 27 ext{ u}$)
(iii) Calculate $\log ext{K}_c$ for the followin...
(a) Why is lead storage battery regarded as a secondary cell?
(b) Give two examples of the fuels used in the fuel cell.
(a) (i) A cell and its emf is given below :
$\text{Pt (s) | H}_2\text{ (g, 1 bar) | H}^+\text{ (aq, 1M) || Cu}^{2+}\text{ (aq, 1M) | Cu (s)}$
emf of the cell $= + 0\cdot34\text{ V}$.
Write the reduction half-reaction at cathode.
(ii) How is standard Gibbs energy for a reaction related to equilibrium...
(i) State Kohlrausch's law of independent migration of ions. (ii) How much electricity in terms of Faraday is required to produce 40 g of Al from molten $\text{Al}_2\text{O}_3$ ? (Given : atomic mass of Al = 27 u) (iii) Calculate $\log K_c$ for the following reaction at 298 K : $\text{Zn (s) + Cu}^{...
Which of the following cells is not rechargeable ?
(a) Dry cell
(b) Lead storage battery
(c) Ni-Cd battery
(d) Fuel cell
(b) Explain the variation of molar conductivity with concentration for strong electrolyte and weak electrolyte with the help of diagram.
(a) Write anode, cathode and overall reaction of fuel cell.
OR
(b) (i) State Faraday's first law of electrolysis.
(ii) Why does the conductivity of a solution decrease with dilution ?
Write the Nernst equation for the following cell reaction :
Zn(s) + Cu^{2+} (aq) → Zn^{2+} (aq) + Cu(s)
How will the E_{\text{cell}} be affected when concentration of
(i) Cu^{2+} ions is increased and
(ii) Zn^{2+} ions is increased ?
In the plot of molar conductivity ($\land_m$) Vs. square root of concentration ($\sqrt{C}$), following curves are obtained for two electrolytes X and Y : Answer the following : (i) Predict the nature of electrolyte X and Y. (ii) What happens on extrapolation of $\land_m$ to concentration approaching...
(i) State Kohlrausch's law of independent migration of ions.
(ii) Calculate the degree of dissociation ($\alpha$) of $\text{CH}_3\text{COOH}$ if $\land_m$ and $\land^\circ_m$ of $\text{CH}_3\text{COOH}$ are $48\text{ S cm}^2\text{ mol}^{-1}$ and $400\text{ S cm}^2\text{ mol}^{-1}$ respectively.
Define molar conductivity for the solution of an electrolyte. How does it vary with concentration?
The molar conductivity of $\text{CH}_3\text{COOH}$ at infinite dilution is $390 \text{ Scm}^2/\text{mol}$. Using the graph and given information, the molar conductivity of $\text{CH}_3\text{COOK}$ will be:
a. $100 \text{ Scm}^2/\text{mol}$
b. $115 \text{ Scm}^2/\text{mol}$
c. $150 \text{ Scm}^2/\tex...
*FOR VISUALLY CHALLENGED LEARNERS
*5. What is the molar conductance at infinite dilution for sodium chloride if the molar conductance at infinite dilution of $\text{Na}^+$ and $\text{Cl}^-$ ions are $51.12 \times 10^{-4} \text{ Scm}^2/\text{mol}$ and $73.54 \times 10^{-4} \text{ Scm}^2/\text{mol}$ r...
Corrosion is an electrochemical phenomenon. The oxygen in moist air reacts as follows: $\text{O}_2(\text{g}) + 2\text{H}_2\text{O}(\text{l}) + 4\text{e}^- \rightarrow 4\text{OH}^- (\text{aq})$. Write down the possible reactions for corrosion of zinc occurring at anode, cathode, and overall reaction ...
b. Write the reaction occurring at anode and cathode and the products of electrolysis of aq KCl.
c. What is the pH of HCl solution when the hydrogen gas electrode shows a potential of -0.59 V at standard temperature and pressure?
OR
a. Molar conductivity of substance “A” is $5.9 \times 10^3$ S/m and...
The resistance and conductivity of a conductivity cell containing $0.001\text{ M KCl}$ solution at $298\text{ K}$ are $1200\text{ }\Omega$ and $1.5 \times 10^{-4}\text{ S cm}^{-1}$. Calculate its cell constant and molar conductivity.
(i) Why on dilution the $\land_{\text{m}}$ of $\text{CH}_3\text{COOH}$ increases very fast, while that of $\text{CH}_3\text{COONa}$ increases gradually ?
(ii) What happens if external potential applied becomes greater than $E^{\circ}_{\text{cell}}$ of electrochemical cell ?
Write the Nernst equation and calculate emf of the following cell at 298 K :
Cr | Cr^{3+} (0.1 M) || Fe^{2+} (0.01 M) | Fe
Given : E^{\ominus}_{Cr^{3+}/Cr} = -0.75 V
E^{\ominus}_{Fe^{2+}/Fe} = -0.45 V
(log 10 = 1)
Write the Nernst equation and calculate the emf of the following cell at $298\text{ K}$ :
$$\text{Zn} \mid \text{Zn}^{2+} (0\cdot001\text{ M}) \parallel \text{H}^{+} (0\cdot01\text{ M}) \mid \text{H}_2\text{ (g)} (1\text{ bar}) \mid \text{Pt (s)}$$
Given : $E^\ominus_{\text{Zn}^{2+}/\text{Zn}} = -0\...
Write the Nernst equation and calculate the emf of the following cell at 298 K :
$\text{Zn} | \text{Zn}^{2+} (0.1 \text{ M}) || \text{Cd}^{2+} (0.01) | \text{Cd}$
Given : $E^{\ominus}_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \text{ V}$
$E^{\ominus}_{\text{Cd}^{2+}/\text{Cd}} = -0.40 \text{ V}$
$(\log 10 =...
Read the passage given below and answer the questions that follow : $1+1+1+2=5$
Oxidation-reduction reactions are commonly known as redox reactions. They involve transfer of electrons from one species to another. In a spontaneous reaction, energy is released which can be used to do useful work. The ...
OR
The molar conductivity of a 1.5 M solution of an electrolyte is found to be $138.9 \text{ S cm}^2 \text{ mol}^{-1}$. Calculate the conductivity of this solution.
The conductivity of $0.001 \text{ mol L}^{-1}$ solution of acetic acid is $3.905 \times 10^{-5} \text{ S cm}^{-1}$. Calculate its molar conductivity. If $\wedge^0_m$ for acetic acid is $390.5 \text{ S cm}^2 \text{ mol}^{-1}$, then calculate its degree of dissociation ($\alpha$).
Answer the following questions (Any two) :
(a) Define Molar Conductivity ($\wedge_m$).
(b) Write the unit of $\wedge_m$.
(c) How does $\wedge_m$ vary with concentration ?
The conductivity of $0\cdot001 \text{ mol L}^{-1}$ solution of acetic acid is $3\cdot905 \times 10^{-5} \text{ S cm}^{-1}$. Calculate its molar conductivity. If $\Lambda^0_m$ for acetic acid is $390\cdot5 \text{ S cm}^2 \text{ mol}^{-1}$, then calculate its degree of dissociation ($\alpha$).
The conductivity of $2\cdot5 \times 10^{-4}\text{ M}$ methanoic acid is $5\cdot25 \times 10^{-5}\text{ S cm}^{-1}$ and its $\Lambda^\circ_{\text{m}}$ has a value $400\text{ S cm}^2\text{ mol}^{-1}$. Calculate its molar conductivity and degree of dissociation.
Define electrochemical cell. What happens if external potential applied becomes greater than $E^\circ_{\text{cell}}$?
Read the passage given below and answer the questions that follow :
An electrochemical cell consists of two metallic electrodes dipping in electrolytic solutions. Electrochemical cells are of two types. In galvanic cell, the chemical energy of spontaneous redox reaction is converted into electrical ...
What happens when external potential applied is greater than $E^\circ_{\text{cell}}$ of electrochemical cell?
How do conductivity and molar conductivity vary with concentration?