Electrochemistry Questions and Answers

6 The values of A for NH4C1 NaOH and NaCl are respectively 149 74 248 1 and 126 4 ohm cm eq The eq value of A NH OH is 1 371 44 2 271 44 3 71 44 Sim228 21

4 AIEEE 2009 2 The Gibbs energy for the decomposition of Al2O3 at 500 C is as follows 7 3 Al O3 4 3 Al 0 AG 966 kJ mol The potential difference needed for electrolytic reduction of Al O3 at 500 C is at least 1 4 5 V 3 2 5 V The reduction potenti 2 3 0 V 4 5 0 V AIEEE 2010

125 The potential of the cell at 25 C is Pt H CH3COONa 0 1 M 1 atm CH COOH 0 01 M NH4C1 H Pt 0 2 M 1 atm NH OH 0 1 M Given pk of CH3COOH and pK of NH OH 4 74 1 0 04 V 2 0 04 V 3 0 189 V 4 0 189 V

10 In passing 3 F of electricity through three electrolytic cells connected in series containing Ag Ca and Al ions respectively The molar ratio in which the three metal ions are liberated at the electrodes is 1 1 2 3 2 2 3 1 3 6 3 2 4 3 4 2 Given that 219 1 2e F 0 54 V

4 Resistance of 0 2 M solution of an electrolyte is 50 22 The specific conductance of the solution is 1 3 S m If resistance of the 0 4M solution of the same electrolyte is 260 2 its molar conductivity is 1 6250 S m mol 2 6 25 x 10 4 S m mol 3 625 x 10 4 S m mol 4 62 5 S m mol AIEEE 2011

c 1 cm d 1 cm 7 The resistance of a decinormal solution of a salt occupying a volume between two platinum electrodes 1 80 cm apart and 5 4 cm in area was formed to be 32 The specific and equivalent conductivity 2 ohm respectively in their proper units are a 104 1 and 0 0104 0 0104 and 104 0 b 208 2 and 0 0208 d none of these

Specific conductance of 0 01 M KCl solution is x ohm cm When conductivity cell is filled with 0 01 M KCl the conductance observed is y ohm 1 When the same cell is filled with 0 01 M H SO4 the observed conductance was z ohm cm The specific conductance of 0 01 M H SO4 is a xz c xz y b z xy d xy z rod for the complete decomposition

34 Ethane gas is obtained in Kolbe s electrolysis of CH COONa according to the following reaction CH 2CH 000 I 200 2e CH What volume of gas ethane gas at S TP would be obtained by a current of 0 5 amp 80 efficient if the current is passed for 965 min a 1 8 L b 2 688 L c 3 45 L d 11 2 L

CHEMISTRY Consider the following E values E LLi 3 05 V E Cu2 Cu 0 34 V Under similar conditions the potential for the reaction Cu 2Lit Cu 2Li is 1 3 39 V 2 3 39 V 3 2 69 V 4 2 69 V

390 7 and for mol The deg solution is a 13 3 18 The equivalent conductance of monobasic acid at infinite dilution is 348 ohm cm eq If the resistivity of the 27 The position solution containing 15 g acid mol wt 49 in 1 litre is 18 5 ohm cm What is the degree of dissociation of acid series in decre Mg Al Zr b 40 2 c 60 4 d 50 7 spoo a 45 9 9 Calculate the emf in V of th

Fused quartz transmits 90 percent of the incident thermal radiation between 0 2 and 4 um Suppose a certain heat source is viewed through a quartz window What heat flux in watts will be transmitted through the material from blackbody radiation sources at a 800 C b 550 C c 250 C and d 70 C

15 A solution contains 10 40M Cu 1 M Zn as the only will be reduced at cathode first Given E Cu 0 34V E a Cu2 b Zn c Both are reduced at same time d None of ion is reduced 6 The standard reduction potential Zn 0 76V Zn Zn C 24 7

How much will the reduction potential of a hydrogen electrode change when its solution initially at pH 0 is neutralized to pH 7 1 Increase by 0 059 V 2 Decrease by 0 059 V 3 Increase by 0 41 V 4 Decrease by 0 41 V

42 For the cell Ni Ni 0 1 M Au 1 0 M Au the value of emf will be if E for Ni2 Ni is 0 25 V E for Au Au is 1 50 V a 1 25V c 1 78 V If bud b 1 75 V d 4 0 V

An aqueous solutions containing IM each of Au Cu Ag Li is being electrolyzed by using inert electrodes The value of standard potentials are E Ag Ag 0 80V Ecuc 0 34V E ALAL 1 50V EL 3 03V With increasing voltage the sequence of deposition of metals on the cathode will be 1 Li Cu Ag Au 2 Au Ag Cu 2 Cu Ag Au 4 Au Ag Cu Li

a P c R 37 Resistance of 0 2 M solution of an electrolyte is 50 2 The specific conductance of the solution is 1 4 Sm is 280 2 The molar conductivity of 0 5 M solution of the The resistance of 0 5 M solution of the same electrolyte 2 electrolyte in S m mol is a 5x10 4 c 5x103 b 5x10 3 d 5 10

Suppose above Fuel cell 25 KOH solution was used as electrolyte For it the anode half reduction potential is 0 83V and cathode half reduction potential is 0 40V What is the EMF of cell If the Fuel cell produces 10 mol of H O how long it can support a 100W electric bulb

aq Cuais unstable in solution and undergoes simultaneous oxidation and reduction according to the reaction 2000 2Cu aq Cu aq Cu s choose correct E for above reaction if E Cu2 Cu 0 34 V and E Cu Cut 0 15 V a 0 38 V c 0 38 V b 0 49 V d 0 19 V

a 32 4 g c 36 0 g equivalent 4 104 b 38 8 g d 22 4 g 48 If 54 g of silver is deposited during an electrolysis reaction how much aluminium will be deposited by the same amount of electric current a 2 7 g b 4 5 g c 27 g 9 The quantity of electricity needed d 5 4 g to to separately

If Aut Au is 1 69 V and Au Au is 1 40 V E then Au Au will be Question Type Single Correct Type 1 E 2 3 0 19 V 2 945 V 1 255 V

The standard electrode potential of Zn Ag and Cu electrodes are 0 76 V 0 80 V and 0 34 V respectively then 1 Ag can oxidise Zn and Cu 2 Ag can reduce Zn and Cu 3 Zn can reduce Ag and Cu 4 Cu can oxidise Zn and Ag FC0017

30 Specific conductance of 0 1 M NaCl solution is 1 01 10 cm Its molar conductance in 2 cm mol is a 1 01 x 102 b 1 01 10 c 1 01 x 104 d 1 01 31 Limiting molar conductivity of NaBr is 38

5 Suppose a galvanic cell employs the following half reactions Ni aq 2 Ni s E Cr aq 3 Cr s E c Ni2 0 25 V Cr3 0 74 V Calculate the cell potential when Ni 4 87 104 M and Cr 2 48 10 M

The following half reactions are provided for 40 each metal Cr aq 3 e Cr s E red 0 744 V Zn aq 2 e Zn s E red 0 763 V Which of the following is the half reaction a that takes place at the anode 0 of 0 25 points earned 3 attempts remaining What is the standard cell potential for this b cell 0 of 0 25 points earned 3 attempts remaining Write the balanced equation for the overall C reaction in acidic solution 0 of 0 25 points earned 3 attempts remaining

c P R was 36 AgNO3 aq was adde measured The plot of conductance A versus the gradually and the conductivity of the solution volume of AgNO3 is a A Volume P Volume R b A d A b Q d S 1 Volume Q Volume S ion

40 How much will the reduction potential of a hydrogen electrode change when its solution initially at pH 0 is neutralised to pH 7 a Increase by 0 059 V b Decrease by 0 059 V c Increase by 0 41 V d Decrease by 0 41 V

29 Calculate molar conductivity of 0 15 M solution of KCI at 298 K if its conductivity is 0 0152 S cm a 124 2 cm mol b 204 2 cm mol c 101 2 cm mol d 300 2 cm mol

From which solution 2 faraday electrical charge will deposit 1 gram atom weight at cathode Auce 1 Auric chloride 2 Silver nitrate 3 Cuprous chloride Ag No cuce

39 What will be the molar conductivity of Al ions at infinite dilution if molar conductivity of Al SO is 858 Scm mol and ionic conductance of SO2 is 160 Scm mol at infinite dilution a 189 Scm mol b 698 Scm mol c 1018 Scm mol d 429 Scm mol

Water is reduced to H at 298 K according to the given reaction H O e 1 H g OH aq The reduction potential of the above half cell at standard state is x V then the value of 10 x is where represents greatest integer function Use 2 303RT F 0 059 and K 10 4 at 298 K Answer 0 1 2 3 4 5 6 7

Consider the following solutions Solution P aq solution of Cu NO3 2 Solution Q aq solution of AgNO3 Solution R conc aq solution of NaCl Solution S aq solution of KNO3 If electrolysis of these solutions takes place using in electrodes in different containers Among the following set of the solution s in which pH does not increase due to electrolysis is are assume no volum change due to electrolysis

c 390 2 Resistance of a conductivity cell filled with a solution of electrolyte of concentration 0 1 M is 100 2 The conductivity of this solution is 1 29 S m Resistance of the same cell when filled with 0 2 M of the same solution an

The Ksp of Ag2 CrO4 AgCl AgBr and Agl are respectively 1 1 x 10 12 1 8 10 10 5 0 x10 13 8 3 x 10 17 Which one of the following salts will precipitate last if AgNO3 solution is added to the solution containing equal moles of NaCl NaBr Nal and Na CrO4 1 AgCl 2 AgBr 3 Ag CrO4 4 Agl

4 The equivalent conductivity of monobasic acid at infinite dilution is 348 ohm cm eq If the resistivity 1 of the solution containing 15 g acid molar mass 49 in 1 litre is 18 5 ohm cm what is the degree of dissociation of acid a 45 9 c 60 4 b 40 2 d 50 7

07 3 moles of KMnO4 reacts completely with 9 10 moles of X in acidic medium to give XO3 and Mn2 Value of n will be O 10 3 O 2 3 05 3 Marks 4 1 5 62 66 70 74

The equivalent conductances of two strong electrolytes at infinite dilution in H O where ions move freely through a solution at 25 C are given below ACH COONa 91 0 S cm equivalent What additional information quantity one needs to calculate of an aqueous solution of acetic acid What additional information quantity one needs to calculate of an aqueous solution of acetic acid 1 A of chloroacetic acid CICH COOH 2 A of NaCl 3 A of CH COOK 4 The limiting equivalent conductance of H 2

Consider the electrochemical cell Zn Zn Ag Ag 0 01 M 1L 0 1 M 1L EAg Ag 0 8 V E2n 2 0 77 V If x L of H O is added in anodic chamber and y L of H O is added in cathodic chamber such that emf of cell is more than E at 298 K The possible value of x and y are A 9010 B 254 C 315 D 133

An aqueous solution containing 0 01 M Fe CIO4 3 0 01 M Fe CIO4 2 and 0 01 M HCIO was titrated with a concentrated solution of NaOH at 30 C so that changes in volumes were negligible Calculate the redox potential of Fe Fe2 electrode at pH values 2 2 4 2 6 0 8 2 and 10 assuming that new species formed during titration were Fe OH 3 and Fe OH 2 only Given Ksp of Fe OH 3 10 37 1 Fe3 Fe2 0 77 V Ksp of Fe OH 10 18 4

A graph is plotted between Ecell and log Zn Cu linear with intercept on Eell axis equals to 1 10 V Calculate Ecell for the cell 2 Zn s Zn 0 1 M Cu 0 01 M Cu The curve is

Consider these generic half reactions Half reaction X aq eX s y aq 2e Y s Z aq 3e Z s 1 Identify the strongest oxidizing agent Ox Oz Oz OY Ox OY E V 1 49 0 70 1 22 Identify the weakest oxidizing agent Oz Ox OY OY Ox Oz

Given NO30 NO acidic medium HD E 0 8 V NO3 NH OH acidic medium E 0 74 V At what pH the above two half reactions will have same EMF values Assume the concentration of all the species to be unity Take 0 059 0 06

25 The molar conductivity of HCl NaOH and CH3COONa are 425 188 96 S cm2 mol lat 298 K The molar conductivity of CH3COOH at the same temperature is Scm mol a 333 c 325 b 451 d 550 01 M weak acid is

5 The equivalent conductivity of 0 1 M weak acid is 100 times less than that at infinite dilution The degree of dissociation of weak electrolyte at 0 1 M is a 100 c 0 01 b 10 d 0 001 tivities of a uni univa

36 X gm of ethanal was subjected to combustion in a bomb calorimeter and the heat produced is Y Joules Then a AE XJ b AE YJ combustion combustion combustion combustion C AE d AH 7 Enthalny 44Y X J mol 1 44Y X J mol

2 2 dichloro propane on hydrolysis yields 1 Acetone 2 2 2 Propane diol 3 Isopropyl alcohol 4 Acetaldehyde E of Fe Fe 0 44V E of Cu Cu 0 34 V Then in the cell 1 Cu Oxidizes Fe 2 Fe Oxidizes Cu 3 Cu Reduces Fe 4 FeReduces Cu

1 Identify the complete redox reaction for a Zn Zn2 Cu Cu cell A Zn s Cu aq Zn aq Cu s Zn aq Cu aq Zn s Cu aq Zn aq 2 Cu aq B Zn s Cu s C Zn aq Cu s D Zn s 2 Cu s s 2 Identify the complete redox reaction for a Zn Zn Pb2 Pb cell aq Pb aq Zn s Pb aq Zn aq 2 Pb s 7 21 Phal A Zn s Pb s Zn B Zn aq Pb s C Zn s 2 Pb aq 2 Choose Choose

When 1 mole of an ideal gas at 20 atm pressure and 15 L volume expands such that the final pressure becomes 10 atm and the final volume become 60 L Calculate entropy change for the process Cpm 30 96 J mole 1 K 1 80 2 J k Imo1 1 2 62 42 kJ K 1 mol 1 3 120 x 102 J1c mol 1

6 Match the standard reduction potentials for each half reaction and the electric potential for the voltaic cell Given half cell Be Be reduction half reaction Be 2e Be half cell Hg Hg reduction half reaction Hg 2e Hg anode Be cathode Hg

The molar conductivities of Mg HCOO 2 MgCl2 and HCI are 230 280 and 425 Scm mol1 respectively Calculate molar conductivity of HCOOH Question Type Single Correct Type 1 2 3 4 400 Scm mol 1 80 Scm mol 1 40 Scm mol 1 160 Scm mol 1

Write the Nernst equation for the following half reaction and find E when pH 3 00 and PAH 1 00 mbar As s 3H 3e ASH g E 0 238 V A 0 356 V B 0 556 V C 0 356 V D 0 556 V Answer A