Electrochemistry Questions and Answers

Q 12 The E 4 1 00 21 M M values for Cr Mn Fe and Co are 0 41 1 57 0 77 and 1 97 V respectively For which one of these metals the change in oxidation state from 2 to 3 is easiest O Fe OMn 0

Q 16 Zn E for Fe 2e Feis 0 44 V and E for O 4 1 O 00 21 2e 2e Zn is 0 76 V thus Zn is more electropositive than Fe Zn is more electronegative than Fe Fe is more electropositive than Zn

Q 15 O 29 5 10 O At 25 C the standard e m f of cell having reactions involving a two electron change is found to be 0 295 V The equilibrium constant of the reaction is 10t 4 1 10 0 00 35 6

During electrolysis of an aqueous solution of sodium sulphate 2 4 L of oxygen at STP was liberated at anode The volume of hydrogen at STP liberated at cathode would be Question Type Single Correct Type 1 1 2 L 2 2 4 L 3 2 6 L 401

Q 11 O 2 5 In acidic medium MnO4 is converted to Mn The quantity of electricity in faraday required to reduce 0 5 mole of MnO4 to Mn would be O 5 O 1 4 1 O 05 00 16 O 000

Q 3 moderate 4 1 00 06 The standard reduction potential for Fe and Sn Sn electrodes Fe 0 30 V O are 0 44 V and 0 14 V respectively For 0 58 V the cell reaction Fe Sn Fe Sn the 2 2 standard e m f is Gabion willen

Electrolysis can be used to determine atomic masses In a solution a current of 0 550 A deposits 0 55 g of a certain metal in 100 minutes Calculate the atomic mass of the metal if eq Wt molar wt 3 Question Type Single Correct Type 1 100 2 45 0

Identify the reaction from following havingtop position in EMF series Std red potential according to their electrode potential at 298 K 2 Mg 2e Mg s Fe2 2e Fe s Au 3e Au s 3 CORRECT ANSWER

7 Molar conductivity of NH4OH can be calculated by the equation a A NH4OH A Ba OH 2 A NH CI A BaCh b A NH4OH ABaCl A NH4Cl A Ba OH 2 NH C 4 c A NH4OH d A NH OH A Ba OH Ba OH 24 A NHACI 20 A Ba OH BaCl Quaros 0

Consider the reaction Cl g 2Br aq 2Cl aq Br The emf of the cell when CH Br Br 0 01 M and Cl gas at 1 a pressure will be E for the above reaction is 0 volt 1 0 54 volt 3 0 24 volt 2 0 35 volt 4 0 29 volt

The standard reduction potentials of Cu Cu an Cu Cut are 0 337 and 0 153 V respectively The standard electrode potential of Cut Cu half ce is 1 0 184 V 3 0 521 V 2 0 827 V 4 0 490 V

The heat of neutralisation of a strong acid and a strong alkali is 57 0 kJ mol 1 The heat released when 0 5 mole of HNO3 solution is mixed with 0 2 mole of KOH is A B C D 57 0 kJ 11 4 kJ 28 5 kJ 34 9 kJ

5 Following reactions are taking place in a Galvanic cell Zn Zn 2e Agt e Ag 2 Which of the given representations is the correct method of depicting the cell a Zn s Zn aq Ag aq Ag s b Zn Zn Ag Agt 2 2 c Zn aq Zn s Agt s Ag aq 2 d Zn Ag Zn aq Ag s

The value for the standard emf electromotive force of a galvanic cell described by the balanced chemical equation is 0 79 V Determine the value of the standard half cell potential for the I 12 couple Cr202 7 aq 21 aq 12 g Cr3 aq E Cr 20 7 2 Cr 3 1 33 V A 0 18 V B 0 18 V C 0 54 V D 0 54 v

The standard electrode potentials for the reactions Ag s Ag aq e Sn aq 2e Sn s at 25 C are 0 80 volt and 0 14 volt respectively The standard emf of the cell Sn Sn 1M Ag 1M Ag is 1 0 66 volt 2 0 80 volt 3 1 08 volt 4 0 94 volt

The cell reaction for the given cell is Pt H pH 2 pH 3 Pt H P 1 atm P2 1 atm a spontaneous c in equilibrium b non spontaneous d either of these ricity is passed through CuSC

For the redox reaction Zn s Cu 0 1M Zn 1M Cu s taking place in a cell E Cell is 1 10 volt Ecell for the cell will be RT F 2 303 1 1 07 volt 3 2 14 volt 0 0591 2 0 82 volt 4 1 80 volt

monobasic acid is 4 S cm mol 1 and a infinite dilution is 200 S cm mol 1 Dissociation constant of this acid is 10 3 4 x 10 6 2x 10 5 10 4

At 25 C the standard emf of cell having reactions involving two electrons change is found to be 0 295 V The equilibrium constant of the reaction is 1 29 5 x 10 2 3 1010 2 10 4 29 5 1010

Given that Ni Ni 0 25 V Cu Cu 0 34 V Ag Ag 0 80 V Zn Zn 0 76 V Which of the following reactions under standard condition will not take place in the specified direction ON Cu s Ni s Cu aq 2Agaq Cu s 2Ag s Cuq Zn s Cu 2 Znaq Cu s 2H aq Zn s H g Znaq

3 In which cell liquid function potential need to be eliminated a Pt H2 A HC1 Pt H2 P Pt H HC1 HC1 Pt H C1 C2 CHE c Nicad cell d Lond storage battery I mill Tivo liq present Ag mg cl

5 0 m mol dm 3 aqueous solution of KCl has a conductance of 0 55 ms when measured in a cell of ell constant 1 3 cm 1 The molar conductivity of this solution is mSm mol 1 Round off o the Nearest Integer Answer

Standard enthalpy of vaporisation AvapH for water at 100 C is 40 66 kJ mol The internal energy of vaporisation of water at 100 C in kJ mol is a 37 56 b 43 76 c 43 76 d 40 66 Assume water vapour to behave like an ideal gas

0 23 10 19 d 0 32x10 25 In the electrolysis of CuCl2 solution using Cu electrodes the mass of cathode increases by 3 18 g What happened at the other electrode a 0 05 mole of Cu b 0 112 litre of Cl2 was liberated Iions passed into solution c 0 56 litre O2 was liberated d 0 1 mole of Cu2 ions passed into the solution fH is M 2

In the electrolysis of AgNO3 the mass of Ag deposited is plotted against the charge mass of Ag deposited slope of line tan 0 0 Q Charge Slope of the line gives 1 Equivalent mass of silver 2 Electrochemical equivalent of silver 3 value of faraday 4 Current passed through the cell

A layer of 0 25 mm thick chromium metal is to be electroplated on the rims of autovehicle with a total area of 32 m from a solution of Cro What amount of electric current is required for electroplating the rims in 60 sec The density of chromium metal is 7 2 g cc A 4 9 10 A B 1 78 10 A 5 3 10 A D 10 69 x 106 A

18 Standard electrode potential for Sn 3 Sn 2 couple is 0 15 V and that for the Cr Cr couple is 0 74 V These two couples in their standard state are connected to make a cell The cell potential will be a 1 83 V c 0 89 V AIPMT P 2011 b 1 19 V d 0 18 V Y Y and

ven the standard electrode potentials K 2 93 V Ag Ag 0 80 V Hg Hg 0 79V Mg2 Mg 2 37 V Cr Cr 0 74V Arrange these metals in their increasing order of reducing ower OK Mg Cr Hg Ag O Ag Hg Cr Mg K O Ag Cr Hg Mg K OK Mg Hg Cr Ag

Gem stone Bredig s Arc method is suitable for making which of the following sols Gold sols Mark Tor Review Basic dye 01 2 hr mi

5g of aluminium at mass 27amu is deposited at cathode from a solution by a certain quantity of electric charge The volume of hydroge produced at STP from ions in solution by the same quantity of electric charge will be O O O O 22 4 L 44 8 L 5 6 L 11 2 L

H g Pt s Anode Voltmeter K NO HCI Cathode Cl g By what value the cell valtage change when concentration of ions in anodic and cathodic compartments both increased by factor of 10 at 298 K A 0 0591 B 0 0591

A of 0 01M MgCl is 220 S cm mol X of MgCl is 240S cm mol 1 A of Mg2 is 100 S cm mol 1 All above measurements are done in an electrolytic cell Assuming MgCl to be a strong electrolyte which of the following is correct Limiting equivalent conductivity of MgCl is 480 S cm eq O A of MgCl varies linearly with concentration O of 0 04M MgCl will be 160 S cm mol O A A of 0 04M MgCl will be 200 S cm mol

A cell contains two hydrogen electrodes The negative electrode is in contact with a solution of 10 6 M H ions The emf of the cell is 0 118 volt at 25 C The H at positive electrode is

the difference of two electrode potential val ues corresponds to a positive electrode pot ential and consequently negative change in Gibbs free energy in equation then the less r eactive metal will come out of the solution a nd the more reactive metal will go into the s olution tell me the mechanism how this hap pens

Non stoichiometric cuprous oxide Cu 0 can be prepared in laboratory In this oxide copper to oxygen ratio is slightly less than 2 1 Select correct statement It shows metal deficiency defect O O This substance can act as p type semiconductor In this compound copper exist as 1 2 oxidation state All of these

The corrosion of iron is an electrochemical process that involves the standard reduction potential given here at Fe ag 2e Fe s E 0 44 V O g 4H ag 4e 2H O l E 1 23 V The voltage if the reaction occurs at pH 4 0 but all other concentration are maintained as they were in the standard cell Given 2 303 RT F 0 06 V O O O 1 43 V 1 67 V 0 44 V

14 Consider the following reaction Cu Zn Zn Cu a Depict the galvanic cell in which the given reaction takes plac b Give the direction of flow of current c Write the half cell reaction taking place at cathode and anod

400 mL of aqueous CuSO4 solution was electrolysed using Pt anode and Cu cathode A constant current of 3 2 mA was passed for 28 95 min It was found that after electrolysis the absorbance of the solution was reduced by 50 of its original value Calculate the concentration of CuSO in the solution to begin with Take 1 F 96500 C mol O 1 44 10 M 02 88 10 5 M 7 2010 M O 43210 5 M V

Mg s 2Ag 0 0001M E Electrochemistry 1 1 85 V 3 4 65 V cell Mg2 0 130M 2Ag s af E 3 17 V cell 2 2 96 V 4 3 12 V 8 0 0 1

For formic acid HCOOH HCOO H Ka 1 7 10 4 calculate concentration of H ions present in the mixture of 0 1 M HCOOH and 0 05 M HCOONa solutions Question Type Single Correct Type 1 2 3 A 3 4 x 10 4 M 8 5 x 10 5 M 4 1 x 10 3 M

he conductivity of a saturated solution of AgCl is 9 x 10 6 sm and its molar conductivity at infinite dilution is 3 1 p of AgCl is A B 9 10 10 4 32 x 10 18 1 8 10 9 X 5 10 16

4 Very weak metallic bond 54 Calculate the equilirium constant for the reaction Fe 2 Cet Fe Ce Given Ee C 3 1 44 V E2 0 68V 2 303RT F 0 06 at 25 C log 4 68 0 67 1 K 5 x 108 2 K 4 68 x 10 2 3 K 2 x 104 4 None 76 06 12 6 54 fe Fe f Cath 1 44 62 76 19 6 Kc C 2

D 2 In argalvanic cell the salt bridge A does not participate chemically in the cell reaction B stops the diffusion of ions from one electrode to another C is necessary for the occurrence of the cell reaction D ensures mixing of the two electrolytic solutions

0 52 94 The equilibrium constant for the 298 K is Zn s Fe 2 aq Zn given Alum furni 2 aq Fe s Ecell 0 2905 V at 298 K br b 100 595 0 76 d 100 32 0 0295 a e 0 32 0 0295 c 100 0250 0 32 he standard electrode potential for the change a

4 Ag Mg Hg Cr K 3 Mg K Ag Hg Cr 4 Ag Mg Hg Cr K 18 The spntaneous redox reaction s among the following is 18 ffald are a 2Fe Fe3Fe 44 b Hg Hg Hg c 3AgCl NO 2H O Given that E Fe Fet EHg Hg 0 77V 1 a 3 a b 0 85 V EAgCV Ag 0 22 V 3Ag 3Cl NO3 4H Efe Fe 0 44 V Eg H92 ENO NO 0 96 V 2 a b c 4 a c 0 92 V a 2Fe Fe b HgT c 3AgCl NO 2H O 2 2 f EO Fe Fet EHg Hg E AgCl Ag 1 a 3 a b Hg 0 77V 0 85 V 3Fe Anod 0 22 V Hg 5 3Ag 3Cl NO3 4H Fe Fe 0 44 V EHgH9 E NO NO 2 a 4 0 92 V A 0 0

c by de How much will the reduction potential of a hydrogen electrode change when its solution initially at pH 0 is neutralised to pH 7 b Decrease by 0 059 V d Decrease by 0 41 V a Increase by 0 059 V c Increase by 0 41 V harge required for the reduction of 1 mole of

Copper reduces NO3 into NO and NO2 depending upon the concentration of HNO3 in solution Assuming fixed Cu and PNO PNO the HNO3 concentration at which the thermodynamic tendency for reduction of NO3 into NO and NO2 by copper is same is 10 M The value of 2x is Rounded off to the nearest integer Given E 0 34 V E 0 96 V Cu Cu NO NO RT ENO NO 0 79 V and at 298 K 0 79 V and at 298 K 2 303 F 3 0 0591

r Q 14 O H S O The product obtained at anode when 50 H SO aqueous solution is electrolysed using platinum electrodes is O H SO3 O 0 4 1 C 00 20

If 0 50 L of a 0 60 M SnSO4 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 final concentration of Sn remaining in the solution at wt of Sn 119 1 0 342 M 2 0 6 M 3 0 389 M 4 0 514 M

A current of 2 ampere is passed through copper and silver voltameters connected in series If 1 08 gm silver equivalent weight 108 is deposited on cathode in silver voltameter then find the amount of copper deposited at cathode in copper voltameter Given equivalent weight of Cu 31 8