Electrochemistry Questions and Answers

Electrode potential of the half cell Pt s Hg 1 Hg Cl s Cl aq can be increased by b Decreasing Cl d Decreasing Hg 1 30 a Increasing Cl c Increasing Hg Cl s The equilibrium co on stant fon for th foll

E Mg2 Mg 2 37V E Ag Ag 0 8 V Calculate E and E for the cell Sn Sn 1M Pb 10 M Pb E Sn Sn 0 14V E Pb Pb 0 13V Is cell representation is correct Cult in a solution of CuSO will the electrode potential be zero at 25 C

EMF of Daniell cell was found using different concentrations of Zn ion and Cu2 ion A graph Zn Cu The plot was found to be linear with intercept on axis equal to 1 10 V Ecell for Zn Zn 0 1M Cu2 0 01M Cu will be 1 1 10 V 3 0 93 V was then plotted between Eell and log Ecell 2 1 0705 V 4 0 078 V

Al2O3 is reduced by electrolysis at low potentials and high currents If 4 5x 104 A of current is passed through molten Al2O3 for 6 h what mass of aluminium is produced Assume 100 current efficiency at mass of Al 27 g mol a 9 0 10 g c 2 4 105 g b 8 1 104 g d 1 3 104 g

33 Calculate the emf of the cell Pt H 1 0 atm CH COOH 0 1 M NH aq 0 01 M H 1 0 atm Pt Given that K CH COOH 1 8 x 10 K NH 1 8 x 10 A 0 92 V a C 0 35 V B 0 46 V D 0 20 V

Calculate the potential of an indicator electrode versus the standard hydrogen electrode which originally contained 0 1M MnO and 0 5M H and which was treated with 50 of the Fe2 necessary to reduce all the MnOto Mn 2 MnO4 8H 5e Mn 4H O E 1 51V 2 303RT F Given 0 06

31 M is not stable and undergoes disproportionation to form M and M Calculate E for M dispropor tionation EM M 0 153 V EM M 0 53 V 1 0 683 V 3 0 754 V 2 0 367 V 4 0 3415 V

0 Volume of gases evolved when dil H SO4 i electrolysed using 2 F at STP 1 22 4 L 2 11 2 L 3 33 6 L 4 4481

final solution was found to be 12 with current efficiency 96 5 An aq solution of 1 0 MASO and 1 0 MAGNO is electrolysed at 298 K If concentration of Ag be brought down before A start to deposit in electrolysis is 10 M What is the value of x 0 08 05 VE Given ed in amp for electrolysis of 300 ml aqueous NaCl solution If after 5 minutes pH of Ehm 2 303RT F

Given the following E values at 25 C Calculate log K for silver bromide AgB sp Ag aq e Ag s E 0 80V E 0 07 V AgBr s e Ag s Br aq Also calculate AG at 25 C for the process AgBr s Ag aq Br aq

36 g H O is electrolysed by passing 3 ampere current What will be time required for complete decomposition in hour 1 17 87 hour 3 35 74 hour 2 15 84 hour 4 25 35 hour

The pressure of H required to make the potential of H electrode zero in pure water at 298 K is a 10 10 atm c 10 14 atm b 104 atm 10 2 atm d NEET I 2016

During the electrolysis of molten sodium chloride the time required to produce 0 10 mol of chlorine gas using a current of 3 A is 1 220 minutes 3 55 minutes 2 330 minutes 4 110 minutes

of the reaction Ecell MnO4 Fe H Mn 2 Fe3 H O is 0 59 2 at 25 C The equilibrium constant for the reaction 1 50 3 1050 2 10 4 105

6 2NH HSO4 H NH4 S O8 Electrolysis NH4 S O 2H O2NH HSO4 H O steam distillation What amount of current have to be used in first reaction to produce enough intermediate to yield 102 g pure H O per assume current efficiency is 50 2 A 9650 C C 4 10 C B 245000 C D 1158000 C 115

Calculate E and E for the cell Sn Sn 1M Pb 10 M LPb EO Sn Sn E Pb2 Pb 0 13V Is cell representation correct

22 In two vessels each containing 500ml water 0 5 millimol of aniline K 10 2 and 25 m mol of HCl are added separately Two hydrogen electrodes are constructed using these solutions Calculate the emfo cell made by connecting them appropriately log5 0 7 Given 2 303RT F 0 06

At 298 K the standard free energy of formation of H O is 256 5 kJ mol while that of its ionisation to H OH is 80 kJ mol What will be reversible emt at 298 K of the cell H g 1 bar H IM OH 1M O g 1 bar Fill your answer by multiplying it with 10

E Pb Pb 0 13V Is cell representation is correct At what concentration of Cu in a solution of CuSO4 will the electrode potential be zero at 25 Given E Cu Cu 0 34 V

K value for C H H C H is 5x10 8 atm and K for C H H C H is 5 x 1026 atm at 50 C P Calculate K for the reaction 2H C H C H6 1 2 5 1045 3 1 5 x 10 45 2 21 108 4 2 5 x 10 45

emf of the cell be zero to the reduction 1 The standard electrode potential corresponding 3 Cr e Cr is E 0 407 volt If excess Fe s is added to a solution in which Cr 1 M what will be Fe when equilibrium is established at 25 C Fe 0 42 M 2 Fe s 2Cr Fe 2Cr

46 A fully charged lead storage battery contains 1 5 L of 5 M H2SO4 During discharging of lead storage acid battery following reaction takes place Pb s PbO2 s 2H2SO42PbSO4 s 2H O If 2 5 A of current is drawn for 965 min H SO4 consumed in moles is

The equivalent conductivity of KCl at infinite dilution is 130 S cm eq The transport number of Cl ion in KCl at the same temperature is 0 505 The limiting ionic mobility of K ion is a 6 67 x 104 cm s V 1 b 5 01 x 10 3 cm s V 1 c 3 22 x 10 cm s V 1 d 2 00 x 104 cm s 1 V 1

The standard reduction potentials for the following reactions are given below Pyruvate 2H 2e lactate E 0 190 V NAD 2H 2e NADH H E 0 320V What is AG for the overall spontaneous reaction make use of the relationship between AE and AG O Ok J mol O 25 kJ mol O 15 kJ mol O 25 kJ mol

136 E for the cell Zn Zn2 aq Cu 2 aq Cu is 1 10V at 25 C the equilibrium constant for the reaction Zn Cu2 aq Cu Zn2 aq is of the order of a 10 28 c 10 18 b 10 3 d 10 17 Karnataka CET Med 2012

The standard emf of the celloltot odi quoe roshura A car Ag s Cd CdC12 aq 0 1 M AgCl Agenci abvd in which the cell reaction is UM 2C1 is 0 6915 V aq Cd 2AgCl2Ag Cd aq at 0 C and 0 6573 V at 25 C The enthalpy change of the reaction at 25 C is a 48 179 kJ c 123 5 kJ b 234 7 kJ d 167 26 kJ

sed on the equations for today s reaction 2 2 5 03 1 S406 21 Cu 41 2 Cul s 1 w many moles of copper would be used in a reaction that needed 5 mol of S 0

25 g of a metal is deposited on cathode during electrolysis of metal nitrate solution by a current of 5 ampere passing for 4 hours If atomic weight of metal is 200 the valency of metal in metal nitrate is n What is n

800 milliampere of current is passed aqueous for a at anode sol period of of cusof using two 20 minutes predict products cathode estimate quantity of products 63 6 At uit of cu is through an Pt electrode

The conductivity of 0 0099 mol L benzoic acid is 4 95 x 10 5 S cm Its K x 10 6 dissociation constant If L for benzoic acid is 500 S cm mol at th temperature then find x Answer in nearest integer

9 One litre of a gas weighs 2 g at 300 K and 1 atm pressure If the pressure is made 0 75 atm at which of the following temperatures will one litre of the same gas weigh one gram a 450 K b 600 K c 800 K d 900 K

Which of the following is wrong 1 Ecell R P of Cathode R P of Anode 2 Ecell O P of Anode O P of Cathode 3 Ecell O P of Anode O P of Cathode 4 Ecell O P of Anode R P of Cathode

1 20 2H O a e b OH E 0 4 V vs NHE Zn c OH Zn OH d e E 1 25 V vs NHE Please determine the value of a b c d and calculate the maximum energy that can be generate by of Zn air battery use tne units in J per 1 mole Zn

4 Balance the following reaction in acidic condition and compute for the AG O2 g Cu s Cu H O Electrode potentials for the half reaction are 1 23 V and 0 34 V for the Oxygen half reaction an Copper half reaction respectively

Calculate the potential developed by a voltaic cell using the following reaction if all dissolved species are 0 085 M 2 Fe You may need to use the following data aq H O aq 2 H aq 2 Fe aq 2 H H O aq 2 H aq 2 e 2 Fe aq e Fe aq Potential V 2 H O l E 1 77 V E 0 771 V

APA 1 66V and K of Al OH 3 1 10 33 The reduction potential of sp e above couple i e EOH IAI OH AI at pH 14 is approximately equal to X 0 3 V Find out the value of X to nearest integer

Consider a hypothetical cell X s Yaq Xaq Y s AH 289 5 kJ The standard emf of the cell is 1 2 V If the efficiency of the cell is n the value of is neglect the change in entropy

Calculate the potential delivered by a voltaic cell using the following reaction if all dissolved species are 0 067 M and the pressure of H is 1 2 bar Zn s 2 H O l 2 OH aq Zn OH 2 aq H 8 Use the standard reduction potentials listed below Zn s 4 OH aq Zn OH 4 aq 2 e E 1 22 V 2 H O l 2e H g 2OH aq E 0 8277 Ecoll V

One half cell in a voltaic cell is constructed from a copper wire electrode in a 2 1 x 10 3 M solution of Cu NO3 2 The other half cell consists of a zinc electrode in a 0 25 M solution of Zn NO3 2 Calculate the cell potential You may need to use the following data Zn 2 aq 2 e Zn s E 0 763 V Cu aq 2 e Cu s E E 0 337 V 2 IT

6 g of Zn Hg is dissolved in just sufficient amount of dil HNO3 and the solution s diluted upto 200 ml A Zn electrode is immersed in this solution and EMF of ne cell set up Zn Zn 2 aq H 1 N H2 1 atm Pt is 0 83 V The percentage f Zn in Zn amalgum is Given E2 0 77 V 2 303 RT 0 06 and atomic mass of F In 65 A 5 C 10 B 95 D 90

H g and O g can be produced by the electrolysis of water What total volume in L of O g and H g are produced at STP when a current of 30 A is passed through a K SO4 aq solution for 193 min 1 20 16 CO 19 2 40 32 A 90 64

of different half cells are given red o E 2 Cut2 cu 0 34 V E Zn 2 Zn 0 76 V A Ag Ag 0 80 V E Mg 2 Mg 2 37 V n which cell is AG most negative A Zn Zn 2 1M Ag 1M Ag B Cu Cut2 1M Ag 1M Ag Agt 1M Mg 1M Mg C Ag D ZnZn 2 1M Mg 2 1M Ma

What is the calculated value of the cell potential at 298K for an electrochemical cell with the following reaction when the pressure is 1 20 atm the F concentration is 7 59 10 3M and the Cd2 concentration is 6 72x10 M F2 g Cd s 2F aq Cd aq Answer V The cell reaction as written above is spontaneous for the concentrations given

28 A student wishes to make an electrochemical cell with Ecell 1 0645 V based on 2 Zn s Zn aq Cu aq Cu s at 298 K for which Ecell 1 1030 V If both metal ion solutions are initially of equal molarity which solution needs to be decreased in concentration and by what factor to produce a cell with Ecen 1 0645 V

During electrolysis 4828 4 mg of iodine requires 3671 3 coulombs of electricity for its deposition at the anode Calculate the value of Faraday s constant Ans 96489 25 C na

27 Which of the following represents correct relation between standard electrode po tential and equilibrium constant and choose the correct options from the following codes given below nFE I log K 2 303 RT III log K 0 4342 codes A I II and III are correct C I II and IV are correct Q No 27 nFEo RT nFE II Ke RT IV logK 0 4342 FE RT B II and III are correct D I and III are correct

Express the relation among the cell constant the resistance of the solution in the cell and the conductivity of the solution How is the conductivity of a solution related to its molar conductivity Calculate the degree of dissociation and molar conductivity of ethanoic acid if conductivity of 4 89 X 10 4 M ethanoic acid is 6 78 X 10 5 S cm 1 Given H 429 5 S cm mol and HCOO 49 5 S cm 4

The standard reduction potentials for two half cell reactions are given below Cd aq 2e Cd s E 0 40V Ag aq e Ag s E 0 80V The standard free energy change for the reaction 2Ag aq Cd s 2Ag s Cd aq is given by 115 8 KJ 115 8 KJ

En Zn Identify the incorrect statement from the options below for the above cell 0 76 V Zn rod IZI Salt Bridge ve 1M ZnSO soln Cu rod ve IM Cus soin A If Eext 1 1 V no flow of e or current occurs B If Eext 1 1 V Zn dissolves at anode and Cu deposits at cathode

In electrolytic cell external source of voltage is used to bring about a chemical change One of the simplest electrolytic cell consists of two copper strips dipping in an aqueous solution of copper sulphate If a DC voltage is supplied to the two electrodes then copper ions are deposited on the cathode While at anode Cu is converted to Cu aq At cathode Cu aq Cu s Cu s Cu aq At anode Cu 20 g strip of impure copper and 10 g strip of pure copper are dipped in 2 L 0 1 M CuSO4 aq solution 100 A current is passed for 241 25 s through the solution to cause electrolysis Efficiency of current is 80 Answer the following question based on above stem Cu 63 5 g mol Q What is the total weight of pure copper at cathode after the electrolysis