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NEET Chemistry MCQ
Redox Reactions And Electro Chemistry Mcq
Quiz 11
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Q.1
Chlorine can not displace [ MP PMT 1996]
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a)Fluorine from NaF
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b) Iodine from NaI
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c)Bromine from NaBr
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d)None of these
Explanation
Chlorine is less reactive than FluorineAnswer: (a)
Q.2
Mark the false statement [ MP PET 1998]
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a) A salt bridge is used to eliminate liquid junction potential
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b) The Gibbs free energy change, ΔG is related with electromotive force E as ΔG=-2FE
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c)Nernst equation for single electrode potential is
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d)The efficiency of a hydrogen-oxygen fuel cell is 23%
Explanation
Correct statement is Answer: (c)
Q.3
E° for the cell, Zn|Zn2+(aq) || Cu2+(aq)\Cuis 1.10 V at 25°C. The equilibrium constant for the cell reactionZn + Cu2+(aq) ⇒ Cu + Zn2+(aq)is of order of ..[CBSE PMT 1997]
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a) 10-37
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b) 1037
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c)10-17
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d)1017
Explanation
A equilibrium E=0 thus Answer:(b)
Q.4
In electrolysis of NaCl when Pt electrode is taken then H2 is liberated at cathode while with Hg cathode, it forms sodium amalgam. This is because [ CBSE PMT 2002]
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a) Hg is more inert than Pt
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b) More voltage is required to reduce H+ at Hg than at Pt
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c) na is dissolved in Hg while it does not dissolve in Pt
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d) Conc. of H+ ions is larger when Pt electrode is taken
Explanation
Answer: (b)
Q.5
In the reaction: Cu(s) + 2Ag+(aq) → Cu2+(aq) + Ag(s) the reduction half cell reaction is
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a)Cu + 2e- → Cu2+
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b) Cu -2e → Cu2+
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c) Ag+ + e- → Ag
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d)Ag -e → ag+
Explanation
Answer: (c)
Q.6
What will be the emf for given cell [AIEEE 2002]
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a)
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b)
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c)
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d)none of these
Explanation
R.H.S. 2H+ + 2e- → H2(P2)L.H.S. H2(P2) → 2H+ + 2e- Overall reaction H2(P1) → H2(P2)Answer: (b)
Q.7
Which of the following is a strong electrolyte? [ Pb CET 1994]
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a) Ca(NO3)2
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b) HCN
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c)H2SO3
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d)NH4OH
Explanation
Ca(NO3)2 is salt , strong electrolyte Answer:(a)
Q.8
The standard EMF of Danielle cell is 1.1 V. The maximum electrical work obtained from the Danielle cell is [MP PMT 2002]
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a) 212.3 kJ
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b) 175.4 kJ
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c) 106.15 kJ
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d) 53.07 kJ
Explanation
For Danielle cell n=2 Now Work=nFE Work=2 × 96500 × 1.1=212.3 kJ Answer: (a)
Q.9
The oxidation potentials of A and B are +2.37 and +1.66V respectively. In chemical reactions ..[Pb CET 1997]
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a) A will be replaced by B
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b) A will replace B
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c)A will not replace by B
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d)A and b will not replace each other
Explanation
Higher the oxidation potential more reactivityAnswer: (b)
Q.10
On the basis of information available from the reaction (4/3)Al + O2 → (2/3)Al2O3, ΔG=-827 kJmol-1of O2 the minimum emf required to carry out an electrolysis of Al2O3 is [ F=96500 C mol-) [ CBSE PMT 2003]
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a) 2.14 V
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b) 4.28 V
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c)6.42 V
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d)8.56 V
Explanation
For electrolysis of Al2O3(2/3)Al2O3 → (4/3)Al + O2Oxidation state of O2 in Al2O3 is -2 and reduce to 0 In left hand side of above equation number of 'O' are 6 Thus (2/3)× 6 ×(-2)=4 electrons are accepted by Oxygen or n=4Now ΔG=-nFE-827,000=-4 × 96500 × VV=2.14 VAnswer: (a)
Q.11
Zn(s) + Cl2 (1atm) → Zn2+ + 2Cl-The E° of the cell is 2.12V. to increase E ..[ DPMT 2003]
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a) Zn2+ concentration should be increased
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b) Zn2+
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c)Cl- concentration should be increased
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d)partial pressure of Cl2 should be decreased
Explanation
from equation Thus if Zn2+ Answer:(b)
Q.12
Which one of the following cells can convert chemical energy of H2 and O2 directly into electrical energy? [ MP PMT 1998]
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a) Mercury cell
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b) Danielle cell
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c) Fuel cell
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d) lead storage cell
Explanation
Answer: (c)
Q.13
Pure water does not conduct electricity because it .. [ manipal PMT 1995]
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a)has low boiling point
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b) is almost unionised
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c)is neutral
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d)is readily decomposed
Explanation
Answer: (b)
Q.14
The standard reduction potential for two reaction are given belowAgCl(s) + e- → Ag(s) + Cl-(aq), E°=0.22VAg+(aq) + e- → Ag(s) , E°=0.80Vthe solubility product of AgCl under standard condition of temperature (298K) is given by ..[kerala MEE 2003]
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a) 1.6 ×10-
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b) 1.5 ×10-10
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c)3.2 ×10-8
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d)3.2 ×10-10
Explanation
Subtracting second equation from first we getAgCl(s) → Ag+(aq) + Cl-(aq) , E°=-0.50V From Nernst equation As AgCl is solid its concentration is 1 and equilibrium E=0 Thus E°=0.0591 log[Ag+][Cl-] E°=0.0591 log Ksp -0.5=0.0591 log Ksp log Ksp=-9.8139 Or Ksp1.535 ×10-10Answer: (b)
Q.15
What is the potential of half-cell consisting of zinc electrode in 0.01m ZnSO4 solution at 25°C [ Eoxo=0.763V) [ manipal PMT 2001]
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a) 0.8221 V
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b) 8.221 V
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c) 0.5282V
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d)9.282V
Explanation
Zn2+ + 2e- → Zn Answer:(a)
Q.16
The equivalent conductance at infinite dilution of a weak acid such as HF [ Pb PMT 1998]
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a) Can be determined by extrapolation of measurements on dilute solutions of HCl, HBr and HI
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b) Can be determined by measurement on every dilute HF solutions
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c) Can best be determined from measurements on dilute solutions of NaF, NaCl and HCl
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d) Is an undefined quantity
Explanation
Option 'c' according to Kohlrausch's law Answer: (c)
Q.17
Reaction that takes place at graphite anode in dry cell is ..[MP PET 1996]
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a)Zn2+ + 2e- → Zn(s)
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b) Zn(s) → Zn2+ +2e-
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c)Mn2+ +2e- → Mn(s)
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d)Mn(s) → Mn+ + e- +1.5V
Explanation
Answer: (b)
Q.18
An gives H2 gas with H2SO4 and HCl but not with HNO3 because [ CBSE PMT2002]
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a) Zn acts as oxidizing agent when reacts with HNO3
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b) HNO3 is weak acid than H2SO4 and HCl
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c)In electrochemical series Zn is above hydrogen
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d)NO3- is reduced in preference to hydronium ion
Explanation
Answer: (d)
Q.19
Calculate the standard free energy change for reaction, 2Ag + 2H+ → H2 + 2Ag+ E° for Ag+ + e- → Ag is 0.80V [ ISM Dhanbad 1994]
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a) +154.4 kJ
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b) +308.8 kJ
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c)-154.4 kJ
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d)-308.8 kJ
Explanation
Given potential of Ag is reduction potential, Hydrogen electrode is cathode(0Volt) and Ag is Anode(0.8Volt) Cell potential = E cell=reduction potential of (cathode - Anode) Cell potential E0 = 0-0.8 = -0.8Volts ΔG=-nFe°ΔG - -2 ×96500 ×(-0.80)=154.4kJ Answer:(a)
Q.20
For the cell reaction,Cu2+ [C1(aq)] + Zn(s) → Zn2+ [C2(aq)] + Cu(s)of an electrochemical cell, the change in free energy, ΔG at a given temperature is a function of ..[CBSE PMT 1998]
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a) ln(C1)
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b) ln(C2/C1)
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c) ln(C1 + C2)
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d) ln(C2)
Explanation
from the equations Hence ΔG is the function of ln(C2/C1) Answer: (b)
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