Chemistry - Electrochemistry
Exam Duration: 45 Mins Total Questions : 30
Electrochemical reaction at the anode is oxidation.Which one of the following is not an anodic reaction?
- (a)
\(Cl\longrightarrow Cl+e\)
- (b)
\(Fe^{3+}+e^-\longrightarrow Fe^{2+}\)
- (c)
\(Cu\longrightarrow cu^{2+} +2e\)
- (d)
\(Zn=Zn^{2+} 2e^-\)
Suppose one mole of electrons is passed through three electrolytes in series,containing silver,zinc and ferric ions.Assuming that the cathodic reaction in such cell reduces the cations to the metal,moles of each metal obtained is
- (a)
1 mol Ag,1 mol Zn,1 mol Fe
- (b)
0.5 mol Ag,0.5 mol Zn,1 mol Fe
- (c)
1 mol Ag,0.5 mol Zn,0.33 mol Fe
- (d)
0.5 mol Ag,1 mol Zn,0.33 mol Fe
A current liberates 0.504g of hydrogen in 2 hours.How many grams of copper can be liberated by the same current flowing for the same time in cuprous cyanide solution?
- (a)
12.7
- (b)
15.9
- (c)
31.8
- (d)
63.6
2.5 faraday of electricity are passed through a solution of CuSO4 .The number of gram equivalent of Cu deposited on the anode would be
- (a)
0
- (b)
2
- (c)
1.25
- (d)
1.24
Which of the following process would take place at the anode during the electrolysis of concentrated solution of copper chloride using platinum cathode and carbon anode?
- (a)
\(2Cl^{-}- 2e^{-}\longrightarrow Cl_2\)
- (b)
\(Cu^{2+} +2e^{-}\longrightarrow Cu\)
- (c)
\(4H^{+}+4e^{-}\longrightarrow 2H_2\)
- (d)
\(4OH^{-}-4e^{-}\longrightarrow 2H_2O +O_2\)
Which one of the following does not take place at cathode?
- (a)
\(??Cl^{-}\longrightarrow Cl+e^-\)
- (b)
\(??H^{+}+e^{-}\longrightarrow H\)
- (c)
\(??Ag^{+}+e^{-}\longrightarrow Ag\)
- (d)
\(??Cu^{2+}+2e^{-}\longrightarrow Cu\)
Which one of the following reactions is cathodic?
- (a)
\(Zn\longrightarrow Zn^{2+}+2e\)
- (b)
\(Br\longrightarrow 1/2Br_{2}+e\)
- (c)
\(2H_2O+2e\longrightarrow H_2 +OH^{-}\)
- (d)
\(SO_4{2-}+H_2O\longrightarrow H_2SO_4+1/2o_2+2e\)
The following are balanced half-reaction equations.Which one of them represents reduction process?
- (a)
\(Fe^{2+}\longrightarrow Fe^{3+}+e\)
- (b)
\(Mn_4^{-}+8H^++5e\longrightarrow M^{2+}+4H_2o\)
- (c)
\(H_2S\longrightarrow S+2H^{+}+2e\)
- (d)
\(OH^{-}\longrightarrow 2H_2O+O_2+4e\)
A solution containing one mole \(l^{-1}\) each of \(Cu(NO_3)_2,AgNO_3,Hg_2(NO_3)_2 \) and \(Mg(NO_3)_2\) is electrolysed using inert electrodes.\(E^o\) in volt are: with increasing voltage,the sequence of deposition of metals on the cathode will be
- (a)
Ag,Hg,Cu,Mg
- (b)
Mg,Cu,Hg,Ag
- (c)
Ag,Hg,Cu
- (d)
Cu,Hg,Ag
From the following data
2Hg \(\longrightarrow\) Hg22+ +2e; E0=-0.763 volt.....(i)
Hg\(\longrightarrow\) Hg2++2e; E0=-0.851 volt....(ii)
The E0 values for the half cell
2Hg2++2e \(\longrightarrow\) Hg22+ is
- (a)
1.614 volt
- (b)
-0.088 volt
- (c)
0.088 volt
- (d)
-1.614 volt
The time required in seconds to coat a metal surface of 80cm2 with a 0.005mm thick layer by passing a current of 3 ampere is
- (a)
100s
- (b)
125s
- (c)
1200s
- (d)
150s
A certain current liberated 0.504g of hydrogen in 2 hours.The approximate amount of copper deposited in grams by the same current flowing for the same time in a CuSO4 solution:
- (a)
10 g
- (b)
12 g
- (c)
14 g
- (d)
16 g
The quantity of electricity required required to reduce 12.3g of nitrobenzene to aniline asuming 50% current efficiency is
- (a)
57900 C
- (b)
28950 C
- (c)
115800 C
- (d)
231600 C
The cell constant is product of resistance and
- (a)
molar conductance
- (b)
specific conductance
- (c)
equivalent conductance
- (d)
None
The unit of electrochemical equivalent is
- (a)
coulomb g-1
- (b)
g-ampere
- (c)
g ampere-1
- (d)
g coulomb-1
To reduce Ag+ ions of 3.12 g silver sulphate,the amount of copper required would be
- (a)
0.318 g
- (b)
0.635 g
- (c)
1.0 g
- (d)
NONE OF THE ABOVE
The standard reduction potential E0 Zn2+/Zn is -0.76 v and E0 Fe2+/Fe=-0.45 v Daniel cell is
- (a)
+1.10v
- (b)
-1.10v
- (c)
-0.76
- (d)
-0.42
The standard reduction potentials of Sn2+/Sn,Zn2+/Zn,Fe2+/Fe are respectively -0.14 v,-0.76v and -0.44 v. pick out the correct statement
- (a)
Corrosion of tin can be prevented by coating with Zinc
- (b)
Corrosion of zinc can be prevented by coating with tin
- (c)
Corrosion of zinc can be prevented by coating with Fe
- (d)
Corrosion of iron can be prevented by coating with tin
On passing 0.1 Faraday of current through a copper sulphate solution(2.0molar),the amount of copper deposited at the cathode:
- (a)
2.0 mol
- (b)
1.0 mol
- (c)
0.05 mol
- (d)
0.25 mol
What will be the emf for the given cell? Pt|H2(P1)|H+ (aq) || H2(P2) Pt
- (a)
\(\frac{RT}{F} log \frac{P_1}{p_2}\)
- (b)
\(\frac{RT}{2F} log \frac{P_1}{p_2}\)
- (c)
\(\frac{RT}{P} log \frac{P_1}{p_2}\)
- (d)
NONE OF THESE
In a lead storage battery the reaction that occurs at anode during discharge is
- (a)
\(Pb+SO_4^{2-}\longrightarrow PbSO_4+2e\)
- (b)
\(PbO_2+4H+SO_4^{2-}2e\longrightarrow PbSO_4+2H_2O\)
- (c)
\(PbSO_4+2e\longrightarrow Pb+SO_4^{2-}\)
- (d)
\(PbSO_4+2H_2O\longrightarrow PbO_2+SO_4^{2-}+4H^{+}+2e\)
Given:\(\lambda^{\infty}_+(\frac{1}{2}Fe^{3+})=68 ohm^{-1} cm^2 mol^{-1}\) \(\lambda^{\infty}_+(\frac{1}{2}SO^{2-}_4)=80 ohm^{-1} cm^2 mol^{-1}\) the \(\lambda ^{\infty}_m\) of \(Fe_2(SO_3)_3 \) would be
- (a)
408 ohm-1 cm2 mol-1
- (b)
480ohm-1 cm2 mol-1
- (c)
888 ohm-1 cm2 mol-1
- (d)
None of the above
An electrolyte is a substance which
- (a)
conducts electricity
- (b)
decomposes on heating
- (c)
is basic in nature
- (d)
when dissolved in water, dissociates into ions
Faraday's law of electrolysis are related to
- (a)
atomic number of the cation
- (b)
atomic number of the anion
- (c)
equivalent mass of the electrolyte
- (d)
velocity of the cation
An electrochemical cell can behave like an electrolytic cell when
- (a)
Ecell = 0
- (b)
Ecell > Eext
- (c)
Eext > Ecell
- (d)
E cell = Eext
\({ E }_{ \left( { Ni }^{ 2+ }/Ni \right) }^{ \circ }=-0.25V,\)
\({ E }_{ (A{ u }^{ 3+ }/Au) }^{ \circ }=1.50V.\)
The emf of the voltaic cell, \(\frac { Ni }{ { Ni }^{ 2+ } } \) (1.0M) || Au3+(1.0 M) | Au is
- (a)
1.25 V
- (b)
-1.75 V
- (c)
1.75 V
- (d)
2.0 V
Electrode potential for Mg electrode varies according to the equation
\({ E }_{ Mg^{ 2+ }/Mg }={ E }_{ Mg^{ 2+ }/Mg }-\frac { 0.059 }{ 2 } \quad log\frac { 1 }{ \left[ { Mg }^{ 2+ } \right] } \).
The graph of \({ E }_{ Mg^{ 2+ }/Mg }\ vs\ log\left[ { Mg }^{ 2+ } \right] \) is
- (a)
- (b)
- (c)
- (d)
Given, \({ E }_{ { Cr }^{ 3+ }/{ Cr } }^{ \circ }=0.72V,\ { E }_{ { Fe }^{ 2+ }/Fe }^{ \circ }=0.42V\) The potential for the cell Cr | Cr3+(0.1M) || Fe2+(0.01M) | Fe is
- (a)
0.26 V
- (b)
0.399 V
- (c)
-0.339 V
- (d)
-0.26 V
What is the value of log Ksp for AgI? \(\left( 2.303\frac { RT }{ F } =0.059\ V \right) \)
- (a)
-8.12
- (b)
+8.612
- (c)
-37.83
- (d)
-16.13
Aluminium oxide may be electrolysed at \({ 1000 }^{ \circ }C\)to furnish aluminium metal (atomic mass = 27 u; 1 Faraday=966500 C). The cathode reaction is AI3+ + 3e- \(\longrightarrow \) Al0 . To prepare 5.12kg of aluminium metal by this method, would require
- (a)
5.49 \(\times\) 101 C of electricity
- (b)
5.49 \(\times\) 104 C of electricity
- (c)
1.83 \(\times\) 107 C of electricity
- (d)
5.49 \(\times\) 107 C of electricity