Test: Thermodynamics of Electrochemistry
24 Questions MCQ Test Chemistry for JEE | Test: Thermodynamics of Electrochemistry
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Only One Option Correct Type
This section contains 15 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONLY ONE is correct
Q.
Temperature coefficient of EMF of a cell in terms of entropy change is
is called temperature coefficient of EMF of a cell. Thus,
temperature coefficient of 
The standard reduction potential at 298 K of the reaction,
2H2O + 2e- 
H2 + 2OH- is 0.8277 V
Thus,thermodynamic equilibrium constant for the reaction.
2H2O 
H3O+ + OH- at 298 K is
H2 + 2OH- is 0.8277 V H3O+ + OH- at 298 K is 
Given ,
Thus ,equilibrium constant for the reaction in terms of log k is
2Fe3+ + 3I- 
2Fe2+ + I-3
2Fe2+ + I-3 
Given ,
Thus ,(log Keq) for the reaction Cu2+ +In2+ 
Cu+ + In3+ is
An excess of liquid mercury is added to an acidified solution of 1.0 x 10-3 M Fe3+ .Thus 
is if 5% of Fe3+ remains at equilibrium at 298 K
When equilibrium is set up
EMF of the following cell is 0.2905 V
Zn/Zn2+ (a = 0.1M)|| Fe2+ (a = 0.01M)| Fe
The equilibrium constant for the cell reaction is
[IIT JEE 2004]
The half-cell reactions for rusting of iron are
ΔG° (in kJ) for the reaction is
[IIT JEE 2005]
In rusting of iron, Fe2+ is formed. Thus
The Gibbs free energy for the decomposition of Al2O3 at 800 K is as follows :
2Al2O3 → 4Al + 3O2 , ΔrG = 2898kJ mol-1
The potential difference needed for electrolytic reduction of Al2O3 is at least
n= electrons exchanged = 12 in the given reaction
Given , 
The value of standard electrode potential for the half-reaction is
Fe3+(aq) + e- → Fe2+(aq)
Since, different number of electrons are involved hence
For the reaction, 2H2(g) + O2(g) → 2H2O(l), E0cell = 1.23 V at 298 K
and ΔH0f (H2O) = - 285.8 kJ mol-1 Thus, ΔS° (standard entropy change ) is
n = 4 (four electrons are involved) as
For the reaction ,
Thus , for the reaction
Electron involved are different, hence
Signs are taken as per required reaction
III is obtained as (I) - (II)
Consider the following equations for a cell reaction.
A+B 
C+ D, E0 = x volt, Keq = K1
2A +2B 
2C+ 2D, E0 = y volt, Keq = K2
Then,
When a chemical reaction is m ultiplied/divided EMF of the changed equation remains constant but equilibrium constant is raised to power of that change.
Which of the following statements about the spontaneous reaction occurring in a galvanic cell is always true?
For a spontaneous reaction,
ΔG < 0
Also, ΔG = -nFEcell
∴ -ve = -nFEcell
∴ Ecell > 0
Also, Ecell = 
if equilibrium is reached, Ecell = 0
and Q = Keq
∴ 
To make
Ecell >0
Ecell > Q
For a (Ag-Zn) button cell ,the net reaction is
Zn(s) + Ag2O(s) → ZnO(s) + 2Ag(s)
ΔG0f(Ag2O) = -11.21kJmol-1, ΔG0 f(ZnO) = - 318.3 kJ mol-1
Hence, E°cell of the button cell is
ΔG0f(element, as Zn, Ag) = 0
Thus, ΔG0 (Button cell)
=ΔG0 f (ZnO) - ΔG0 f (Ag2O)
=-318.30 - (-11.21)
=-307.09 kJ mol-1
ΔG0 = -nFE0cell (n=2)
∴ 
for the given reaction
E0cell = 2.73 V
n(electrons exchanged) = 12
(4 Al → Al3+ + 12e-)
F=96500 C mol-1
ΔG0 (element) = 0
∴ ΔG0 (reaction) = -nFE0cell
= -12 x 96500 x 2.73
=3161340 J = 3161.34 kJ
thus,
Matching List Type
Choices for the correct combination of elements from Column I and Column II are given as options (a), (b), (c) and (d), out of which one is correct
Q.
The standard reduction potential data at 298 K is given below:
Match E° of a redox pair in Column I with the values given in Column II and select the corect answer using the codes given below:
In all cases, we use
Equal number of electrons are involved.
The standard potential of the following cell is 0.23 V at 288 K and 0.21 V at 308 K.
Match the parameters in Column I with their values in Column II and select the answer from the codes given below the list.
(i) Temperature coefficient of EMF
Comprehension Type
This section contains a passage describing theory, experiments, data, etc. Two questions related to the paragraph have been given. Each question has only one correct answer out of the given 4 options (a), (b), (c) and (d)
Passage I
The concentration of potassium ions inside a biological cell is at least twenty times higher than the outside. The resulting potential difference across the cell is important in several process such as transmission of nerve impulses and maintaining the ion balance. A simple model for such a concentration cell involving a metal M is
M(s) | M+ (aq, 0.05M), || M+(aq) 1M|M(s) | Ecell | = 77mV
Q.
For the above cell,
Passage I
The concentration of potassium ions inside a biological cell is at least twenty times higher than the outside. The resulting potential difference across the cell is important in several process such as transmission of nerve impulses and maintaining the ion balance. A simple model for such a concentration cell involving a metal M is
M(s) | M+ (aq, 0.05M), || M+(aq) 1M|M(s) | Ecell | = 77mV
Q.
If 0.05 M solution of M+ is replaced by 0.0025 M solution of M+,then |Ecell | would be
Passage II
Given,
ΔG0f(AgCl) = -109kJmol-1, ΔG0f(Cl-) = -129kJmol-1
ΔG0f(Ag+) = 77kJmol-1,
Thus E°cell of the cell reaction is
Ag+(aq) + Cl-(aq) → AgCl(s) is
Passage II
Given,
ΔG0f(AgCl) = -109kJmol-1, ΔG0f(Cl-) = -129kJmol-1
ΔG0f(Ag+) = 77kJmol-1,
Q.
Ksp of AgCl is thus,
For equilibrium, AgCl(s) 
Ag+ + Cl- E0 = -0.59V
-0.59 = 0.0591logKsp
∴ log Ksp = -10
∴ Ksp = 10-10
One Integer Value Correct Type
This section contains 3 questions, when worked out will result in an integer value from 0 to 9 (both inclusive)
Q.
A platinum electrode is immersed in a solution containing 0.1 M Fe2+ and 0.1 M Fe3+.It iscoupled with SHE.Concentration Fe3+ of increased to 0.1 M without change in [Fe2+], then the change in EMF (in centivolt) is
Using Cr2O72- aqueous, solution
E0red = 1.33V and ΔG0 = -770.07 kJmol-1
What is the valency of the ion formed after reduction?
Equilibriumconstant of the cell reaction,
Cu + 2Fe3+ 
2Fe2+ + cu2+ is y x 1014
What is the value of y?
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