Electrochemistry Questions and Answers

4 An electro chemical cell is constructed by immersing a piece of Cu wire in CuSO solution and Zn strip in ZnSO4 solution The emf of cell increases when small amount of concentrated NH3 is added to Given Ecu u 0 34V E 0 76V 10 Zn 2 Zn 1 CUSO Solution 3 Both 1 and 2 2 ZnSO Solution 4 Can t be predicted

Nernst equation is curve is 1 2 3 E E LAY E E E E A Ant 0 059 n EA A 0 0 A 1 log A EAA 0 0 A 1 log A log A 0 0 A 1 A A log A ENA 0 A 1

c 0 91 96 The E values for Cr Mn Fe and Co are 0 41 M3 M2 los sirvi 1 57 0 77 and 1 97V respectively For which one of these metals the change in oxidation state from 2 to 3 mis is easiest a Co c Fe b Mn d Cr 1 00

The standard electrode potential for the two electrode A A and B B are respectively 0 5 V and 0 75 V The emf of the given cell A A a 1 B a 1 B will be O 1 25 V 1 25 V 0 25 V 0 25 V

I 0 5 g of fuming H SO4 oleum is diluted with water This solution is completely neutralised by 26 7 mL of 0 4 N NaOH The percentage of free SO3 in the sample is 1 30 6 2 40 6 3 20 6 4 50 2 MnO 4HCl MnCl 2H O Ch the equivalent wt of HCI will be M Mol wt of HCl 1 M 2 M 2 3 2M 4 M 4 3 Number of moles of MnO 4 required to oxidise one mole of ferrous oxalate completely in acidic medium will be 1 0 6 mole 2 0 4 mole 3 7 5 moles 4 0 2 mole Bro Br 1 0652y Br 1 595 Then the species undergoing disproportionation is BrO 1 2 BrO 5 4 Consider the change in oxidation state of Bromine8 corresponding to different emf values as shown in the diagram below 1 82 V 1 5 V BrO Br 3 4 HBrO HBrO On the basis of the following E 0 values the strongest oxidizing agent is Fe CN Fe Fe e E 0 77 V 1 Fe CN 2 Fe 3 Fe 4 Fe CN 6 In the conversion H SO4 H S O8which process occurs Fe CN e E 0 35 V 1 Oxidation 2 Reduction 3 Oxidation as well as reduction 4 Neither oxidation nor reduction 7 In the reaction 2 Cut Cu Cu the equivalent weight of Cut is M is the mol wt of Cut 1 M M 2 4 1 3 4 2M Valency factor V for following redox reaction is respectively a As2 S AsO 0 b 1 1 10 c H3 PO PH3 H PO3 1 28 3 2 28 3 6 4 7 4 4 3 9 9 The oxidation number of phosphorus in Ba H PO 2 is 1 3 Page

3 4th 49 Bet and a proton are accelerated by the same potential 49 Be 3 fay CREER 4 3rd their de Broglie wavelengths have the ratio 1 1 2 2 1 4 3 1 1 4 1 3 3 Libe and 1 1 2 2 1 4 3 1 1 4 1 3

The elevation in boiling point of a solution of 20 g of a 52 un facta 20g fait face fay del binary electrolyte molecular mass 150 in 200 g of water HIGH GA 150 200 g is A T The value of K for water is 1 347b 4 4AT 3 2 ATB 3 4Tb 2 4 44Tb Thou 23 lot x 5 X 15x200 L dia BAT 4 K 2 4AT 3 AT 4 AT Class XIII Sparta RT OTb kb ko

4 2 If 0 50 L of a 0 60 M SnSO solution is electrolyzed for a period of 30 0 min using a current of 4 60 A If inert electrodes are used what is the fina concentration of Sn2 remaining in the solution at wt of Sn 119 1 0 342 M 3 0 389 M 2 9 6 M 4 0 514 M

0 34 63 Silver is removed electrolytically from 200 mL of a d 0 76 0 34 1 10 V ampere 0 1 N solution of AgNO3 by a current of 0 1 How long will it take to remove half of the silver from the solution b 16 sec a 10 sec d 9650 sec c 100 sec ions the mass of Al The atomic mass of Al is 27 When a current of 5 faraday 3 tion of Al

1 c 1 3 d 1 1 55 A hydrogen electrode placed in a buffer solution of CH3COONa and acetic acid in the ratio s x y and y x has electrode potential values E volt and E2 volt respectively at 25 C The pKa values of acetic acid is E and E2 are oxidation potential E E b 0 118 a c 2212 E1 E2 0 118 d E2 E1 0 118 E1 E2 0 118

4 K CO NO 4J 71 Which of the following will exhibit maximum lonic conductivity 1 K Fe CN6 3 Cu NH3 4 Cl 2 Co NH3 6 Cl3 4 NI CO 4 following complex is not correctly matched

A highly concentrated solution of potassium sulphate in water is electrolysed using iner electrodes The products at the cathode and anode are respectively a H 0 b O H c 0 Na d H s o

Mg 2e Mg E 2 37V When zinc dust is added to the solution of MgCl2 a ZnCl2 is formed b zinc dissolves in the solution c no reaction takes place d Mg is precipitated with normal hyd

20 iv The diagram shows a respirometer used to meansure oxygen uptake by woodi Syringe Perforated basket Woodice Filter paper wick X Manometer What is X a Buffer solution to control the pH b Lime water to indicate the presence of carbon dioxide c Potassium hydroxide solution to absorb carbon dioxide d Water to control the humidity

Select the correct statement s regarding following galvanic cell taken at temperature TK Pt H g 1 bar HCI 10 3 M AgCl s Ag s 2 303RT Given that 0 06volt F Eg AgCl Cr 0 18volt Cell potential of this cell is 0 54 volt During discharging H g converts into H aq H g is obtained at cathode during working of this galvanic cell DE Ag Ag is equal to 0 78 volt if Ksp of AgCl is 1 10 10

Write the cell reaction and calculate the e m f of the following cell at 298 K Sn s Sn 0 004 M H 0 020 M H2 g 1 bar Pt s Given E Sn Sn 0 14 V Log 10 1

26 Calculate the solubility product of Co Fe CN in water at 25 C Given conductivity of saturated solutions of Co Fe CN 6 is 2 06 10 6 21 cm and that of water used is 4 1 10 72 cm The ionic molar conductivities of Co and Fe CN are 86 0 52 cm mol and 444 0 2 cm mol respectively 1 7 87 x 10 7 3 7 87 10 8 2 7 87 x 10 6 4 7 87 10 9

The variation of conductance of the mixture is continuously measured for the titration of a 0 5 M Ba OH 2 solution against 0 5 M MgSO4 solution Which of the following graph best represents the variation of conductance Conductance Conductance Conductance tance Vol of MgSO4 Vol of MgSO4 Vol of MgSO

Which of the following is not correct O O O O Gibbs energy is an extensive property Electrode potential or cell potential is an intensive property Electrical work AG If half reaction is multiplied by a numerical factor the corresponding E value is also multiplied by the same factor

51 What would be the magnitude of the EMF of the following cell 0 1 M acetic acid Pt H 0 1 M sodium acetate 0 1 M formic acid 0 1 M sodium fomate Pt H at 25 C The ionization constant of acetic acid K while that of formic acid K 104 1 0 0295 V 2 0 059 V 3 0 059 V 4 0 0295 V 10 5

6 Given EC 0 7 Cr Based on the data given above strongest oxidizing agent will be EC Cr 0 74 1 CI 2 Mn AIEEE 2012 V EMnO Mn 1 51 V 2 3 1 33 V ECC 1 36 V Cr Cr 2 Cr

Determine the cell potential of an electrochemical cell based on the following two half reactions Oxidation Ni s Ni2 aq 2 0 M 2e Reduction VO aq 0 010 M 2H aq 1 0 M e VO2 aq 2 0 M H O 1

CO O CO AH Y 1 X Y 2 X Y 3 Y 2X 4 2X Y Calculate the standard potential of the cell if the standard electrode potential Zn Zn and Ag Ag are 0 763 V and 0 799V respectively 1 0 036V 2 1 56V 3 1 562V 4 0 799V

Mg s Mg2 0 01M Ag 0 001 M Ag s If a current of 0 5 ampere flows through a water solution for 2 hours then how many lectrons would flow through the cell and how many cm of H is produced at 298 K MH 1 g mol Mo 16 g mol F 96500 C

O Which of the following is correct AC and represent conductance at C concentration and a infinite dilution respectively ANCI AC AC CI H ANaNO3 HNO Naci Anci C ANaNO3 ANO A ac ACI HNO3 ACH COOH 4 CH3COO 4 H

14 Suppose that the concentrations of NaF and KCI were 0 10 M and 0 15M respectively in this cell Pb s PbF s F aq Cl aq AgCl s Ag s a Using the half reactions 2AgCl s 2e 2Ag s 2CT E 0 222V and PbF s 2e Pb s 2F E 0 350V calculate the cell voltage b Now calculate the cell voltage by using the reactions 2Ag 2e 2Ag s and Pb 2e Pb s Solubility product constants are Ksp PbF 3 6 x 10 and AgCl 1 8 x 10

14 Total charge required for the oxidation of two moles Mn304 into MnO in presence of alkaline medium is 1 5F 2 10F 3 20F 4 None of these

The rechargeable lithium ion battery has been developed in Japan The standard electromotive force of the battery is 3 70 V Assume that the reaction at the cathode and anode are when battery is working Cathode CoO Li 1e LiC00 Anode LiC6 6C Li e Electrodes consist of LiCoO2 and graphite The mass of graphite electrode in completely charged state and that in completely discharged state are X g and Y g while 9 8 g of LiCoO2 and 10 g of graphite are present initially Then 10 X Y is Molar mass of Co and Li are 59 and 7 g mol respectively

Consider the following reduction processes Zn 2e Zn s E 0 76 V Ca 2e Ca s E 2 87 V Mg2 2e Mg s E 2 36 V Ni2 2e Ni s E 0 25 V The reducing power of the metals increases in the order JEE Main 2019 1 Ca Mg Zn Ni 2 Ni Zn Mg Ca 3 Ca Zn Mg Ni

3 2 The formal potential of Fe Fe in a sulphuric acid and phosphoric acid mixture E 0 61 V is much lower than the standard potential E 0 77 V This is due to i formation of the species FeHPO4 ii lowering of potential upon complexation iii formation of the species FeSO4 iv high acidity of the medium a i and ii only c iii only b i ii and iv only d all of these

similar amounts of reactants and products 14 a H O 03 H O 20 b H O Ag 0 2Ag H O 0 Role of hydrogen peroxide in the above reactions is respectively 1 oxidizing in a and reducing in b 2 reducing in a and oxidizing in b 3 reducing in a and b 4 oxidizing in a and b

3 In N the N N bond weakness 4 N becomes paramagnetic 5 The equivalent conduce of 1M benzoic acid is 12 8ohm cm and if the conductanc of benzoate ion and Hion at infinite dilution are 42 and 288 42ohm cm respectively Then its degree of dissociation is 1 0 039 2 3 9 3 0 35 7 Which is true for internal energy of system is 4 39

Two complexes A MW 245 g mol B MW 364 g mol Two solutions was prepared from 0 0615 g A in 100 mL water and the second solution prepared from 0 113 g B in 100 mL water The specifi conductivity of A is 625 s and B is 1650 s What is the number of ions for each complex

The standard reduction potentials of Ag Cu Co and Zn are 0 799 0 337 0 277 0 762V respectively Which of the following cells will have maxiumum cell E M F 1 ZnZn 1M Cu 1M Cu 2 2 Zn Zn 1M Ag IM Ag 3 Cu Cu 1M 4g 1M Ag 4 ZnZn 1M Co 1M Co

5 Magnesium oxalate when heated at temperature above 400 C shows a loss in weight due to evolution of a 0 b H O c CO 6 A compact sample will decompose at a d CO CO temperatura than a longa compla

cell 31 In alkaline solution KMnO reacts as follows 2KMnO 2KOH 2K MnO H O O Therefore its equivalent weight will be 1 31 6 2 52 7 3 79 0 158 0 32 The equivalent weight of FeS in the following Oxidation Numbe agent and Reduc Oxidation num respectively 1 6 6 2 5 6 3 6 5 4 5 5

MX mole x2 7 xlo 2 1x10 mx 965 00 5 0800 C of electricity on passing through the electrolyte solution deposited 2 977 of metal with atomic mass 106 4g mol the charge on the metal cation is a 4 c 2 b 3 d 1 ploctrolysis of H O the molar ratio of H and O2

Two electrolytic cells connected in series containing dil H SO4 and dil HCI are electrolysed using platinum electrodes The ratio of volume of gases evolved at the respective anodes is 1 1 1 3 2 3 2 1 2 4 3 4

The mass of a unit cell of CsCl corresponds to 1 8Cs and Cl 2 1Cs and 6CF neet prep 1 1 2 3 1 2 6 3 2 6 3 6 3 0 0 98 Passage of three faraday of charge through aqueous solution of AgNO3 CuSO4 Al NO3 3 and NaCl will deposit moles of metals at the cathode in the molar ratio of High Yielding Test Series Part Test 5 Page Contact Number 9667591930 8527521718 1 Frankel Defect 2 Interstitial Defect 3 F Centres 4 Schottky Defect

Which of the following is most powerful oxidizing agent 1 Cl 2e 2CI E 1 36V 2 Nat eNa E 2 71V 3 MnO 2H O 2e MnO 40H E 0 6V 4 H O 2H 2e 2H O E 1

The voltage of a cell whose half cells are given below is Mg 2e Mg s E 2 37V Cu 2e Cu s E 0 34V Standard EMF of the cell is OU O 1 261 210 7V AY 031

32 B Deduce from the following E values of half cells what combination of two half cells would result in a cell with the largest potential i A eA ii B e iii C 2e iv D 2e E 0 68 V a ii and iii b ii and iv d i and iv c i and iii For the cell prepared from electrode A and B EL 11 33 V and Elect C 133 D E 0 24V 96602 E 1 25 V E 1 25 V 379

11 When iron is added to CuSO4 solution copper is precipitated It is due to 1 Oxidation of Cu 2 2 Reduction of Cu 2 3 Hydrolysis of CuSO4 4 lonization of CuSO4 Oxidation 1 3 1 Which oxidised

Which of the following statements is false A Molar conductance of a strong electrolyte in water decreases as the electrolyte increases B Molar conductance of a weak electrolyte in water decreases as the electrolyte increases at low concentrations C At low concentrations the specific conductance for a strong electolyte in water increases as the electrolyte concentration increases D The specific conductance for a strong electrolyte in water always increases as the electrolyte concentration increases

Under standard conditions hydrogen gas reacts with Au aq aq ions to produce Au s The net cell potential for the reaction is V record answer to two decimal places ie 1 22 and include the sign in your answer do not include units in your final answer

A fuel cell involves combustion of the butane at at latm and 298 K 13 CH10 O4CO 5H 0 x 1 AG 2746kJ mole The value of Eis nearly A 0 8 V B IV C 1 2 V D 1 4

Metal can be prevented from rusting by Question Type Single Correct Type 1 Connecting iron to more electropositive metal a case of cathodic protection 2 Connecting iron to more electro positive metal a case of anodic protection 3 Connecting iron to less electropositive metal a case of anodic protection 4 Connecting iron to less electropositive metal a case of cathodic protection

1000 ml 2 M CuSO4 is electrolysed by a current of 9 65 amp for 2 hours Which is are correct After After electrolysis remaining concentration of Cu 2 is 1 64 M using Cu electrode After electrolysis remaining concentration of Cut2 is 1 64 M using Pt electrode 3 When remaining concentration of Cut2 is 1 822 then volume of solution is reduced by 10 using Pt electrode 17 17 15 gm copper deposit when current efficiency is 75 using copper electrode

Consider the following electrochemical cell at 298K Ag s Agl s 1 aq C aq Hg C Hg Pt s Given Ec creC H 0 26V E 0 8V K Agl 10 and The overall reaction occurring in the above all is 1 Hg Cl s Ag s I aq Hg f Cl aq Agl s 2 Ag aq aq Agl s 3 Hg aq 1 CC aq Hg Cl s 4 Cell reaction is not possible RT 0 06 2 303RT F

One coulomb of charge is passed through a solution of AgNO and CuSO connected in series and the concentration of two solutions are in the ratio 1 2 The ratio of weight of Ag and Cu deposited on Pt electrode is 1 107 9 63 54 3 107 9 31 77 2 4 54 31 77 54 63 54