Electrochemistry Questions and Answers

2 54 For the cell process 101 Sn s Pb 2 aq Pb s Sn aq T ratio of Pb 2 to Sn 2 ion concentration spontaneity is Given EO Sn Sn 2 E 2 0 136 V 0 126 V RM 38

the reaction 6C0313H O 5Br BrO 6HCO Bromine is oxidized and carbonate is reduced Bromine is oxidized and water is reduced Bromine is both oxidized and reduced Bromine is neither oxidized nor reduced A B C D Solm oxidation 2 3B 6C0 3H 0 ON 0 4 Reduction 1 5 5 Br Broz 6HC0 x 2x3 1 21 5

a For the reaction Ag aq Cl aq AgCl s Given Species AG kJ mol 77 129 109 Wote the cell representation of above reaction and calculate E at 298 K Also find the solubilit product of AgCI cell 2 b If 6 539 x 10 g of metallic zinc is added to 100 ml saturated solution of AgCl Find th value of logo Zn Ag How many moles of Ag will be precipitated in the above reaction Given that Ag Ag E 0 80 Ag aq CI aq AgCl s

the three correct options e g the first and fourth options without selecting any incorrect option second option in this case will result in 2 ma fourth option without selecting any incorrect option second option in this case will result in 1 marks Selecting any incorrect option s seconc result in 2 marks The following data are obtained in an experiment Solution 0 01 M HA 100 ml of 0 01 M HA 1 mmol NaOH Given Na 50 2 cm mol H 350 2 cm mol 1 Then select the correct statement Am NaA is 80 2 m mol 1 Am A is 30 1 cm mol 1 Am HA is 38 02 1 cm mol 1 Conductivity 3 8 x 10 5 0 1 cm 1 degree of dissociation of 0 01 M HA is 0 01 80 0 x 10 50 cm 1

Consider the given diagram A B aq If on dipping A in B SO4 aq the colour of the solution changes from colourless to blue then NCERT Pg 279 A and B respectively are colourlers 1 Ag and Cux 2 Cu and Ag 3 Cu and Au

Consider the following unbalanced redox reaction Hg 2 NO3 H Hg HNO2 H O 1M 1M wwwwwww 1M wwwm 1M www w Concentration of ionic species are given at equilibrium If E cell of the given reaction is 0 09 V calculate the minimum pH required to reach equilibrium

A steady current of 1 5 amperes was passed through two electrolytic cells A and B containing CuSO4 and AgNO3 respectively and connected in series If 1 45 g of Ag is deposited at the cathode of cell B than the mass of copper deposited in cell A will be NCERT Pg 94 47 0 43 g 2 0 36 g 3 0 51 g

The half cell potential of a half cell A A Pt were found to be as follows Percent of reduced form 48 8 Cell potential N 0 115 24 4 0 101 Determine the approximate value of n 42 Hm xum

The standard potential of the following cell is 0 23 V at 15 C and 0 21 V at 35 C Pt H g HCl aq AgCl s Ag s 2001 Write the cell reaction i Calculate AH and AS for the cell reaction by assuming that these quantities remain unchanged in the range 15 C to 35 C iii Calculate the solubility of AgCl in water at 25 C Given The standard reduction potential of the Ag aq Ag s couple is 0 80 V at 25 C

2 Consider the cell reaction H g Cl g 2H aq 2Cl aq Equilibrium constant for the cell at 298 K is given E C12 CI 1 20 volt and E H H2 0 volt 1 1040 7 2 1020 7 3 1030 7 4 1050 7

Select the ion of lowest limiting molar conductivity in water at 298 K 0 OH OC Br TYPE questions Each question has 4 choices 1 2 3 and 4 out of which only one is correct Na Read More

Ne at 6 s The oxidation potential of electrode M M N aq 298 K is E When temperature in C is doubled and concentration is made half the electrode potential becomes E Which is correct 1 E E 2 E E 3 E E

166 20 of SO diffuses through a porous partition in 60 seconds Volume of O diffuse under similar conditions in 30 seconds will be B 14 14 l D 28 14 l A 12 14 l C 18 14 l

In electrolysis of acidic water 10 A current is passed for 200 seconds The total volume of the gases evolved at the electrodes at NTP is as a wer 104 Dahod 200 50g Few Day was NTP 3 Jesase sa Dasdealy Jawse augan suasoro dod Options 1 320 ml 2 230 ml 3 348 ml 120 ml

For the cell Pt s Br 1 Br 0 010 M H 0 030 M H g 1 bar Pt s if the concentration of Br becomes 2 times and the concentration of H becomes half of the initial value then emf of the cell 1 Doubles 3 Eight times 2 Four times 4 Remains same

Column l Q1 Electrolysis of aq CuSO4 solution using copper electrodes Q2 Electrolysis of dil H SO4 using inert electrodes Q3 Electrolysis of aq NaF using inert electrodes Q4 Recharging of lead storage battery Column II A1 Density of H SO4 increases A2 No change in molarity of electrolyte solution A3 H is liberated at cathode A4 Positive electrode is anode and negative electrode is cathode A5 O is liberated at anode

Which is symbolic representation 2 Mg s Cl2 g Mg aq 2Cl aq N Red cathad A Pt Cl2 g 1bar Cl aq 1M Mgaq 1M Mg for following cell reactio omrade 11 cathade 2 B Mg Mg 1M Gl2 g 1 bar Cl aq 1 M Pt 2 t Cl aq 1M C12 g 1 bar Mg aq 1M Mg 2 D Mg Mg aq 1M Cl aq 1M Cl2 g 1 bar Pt

During electrolysis of aq CH3COONa solution current of 965 A is passed for 10 second using Pt electrodes select the correct statement s Take 1 F 96500 C mol 1 12 L of H gas at STP is evolved at cathode C H6 gas evolved at anode If the hydrocarbon gas evolved at anode is burnt with excess of O the moles of CO gas evolved is 0 2 During electrolysis total moles of gases evolved is 0 2

When excess of an electrolyte is electrolysed using a direct current source the mass of substance deposited at cathode depends on assume that the same charge is used in each case and same substance is deposited in each case A Temperature B Molten or aqueous electrolyte C Electrochemical equivalent of that substance D Solvent 001100110 0 n nouoou

ow is 2nd statement true 3 pr 9 Function of salt bridge is are a It completes the cell circuit b It allows the movement of ions from one solution to other without mixing of the two solutions c It maintains the electrical neutrality of the solution in two half cells NCERT Pg 66 1 a b 3 Only a 2 a b c 4 b c

During electrolysis of aq NaCl using Pt electrodes variable source 20 current is used where t Current is passed for 965 second 965 then select the correct statement s Take 1 F 96500 C mol Number of moles of H gas evolved is 0 05 Number of moles of O gas evolved is 0 025 Number of moles of Cl gas evolved is 0 05 Number of moles of Cl gas evolved is 0 025

During electrolysis of aq CH COONa solution current of 965 A is passed for 10 second using Pt electrodes select the correct statement s Take 1 F 96500 C mol 01 12 L of H gas at STP is evolved at cathode C He gas evolved at anode If the hydrocarbon gas evolved at anode is burnt with excess of O the moles of CO gas evolved is 0 2 During electrolysis total moles of gases evolved in 0 2

For the following galvanic cell E 0 03 V at 25 C Pt s H g 1 atm H aq 1 M Agt aq 1 M Ag s Calculate the value of AG Ag aq Given 1 F O2895 KJ O 28 95 KJ O 28 95 J 2895 J 96500 C mol

The standard electrode potential of Zn Ag and Cu are 0 76 0 80 and 0 34 volt respectively then A Ag can oxidise Zn and Cu B Ag can reduce Zn and Cu2 C Zn can reduce Ag and Cu2 D Cu can oxidise Zn and Ag

For the reaction 2H O 2H O AH 571 kJ mol 1 Bond energies of H H and O O respectively are 435 and 498 kJ Then average bond energy of O H bond will be Approx 484 3 390 2 271 4 205

4 Consider the following polypeptide chain GDAEVKLRIDFW pka a COOH 2 8 pka R arg 11 8 Given pka a NH 9 8 pKa R glu 4 2 pka R asp 3 2 pKa R lys 10 2 What would be the isoelectric point of this polypeptide chain 2 6 46 4 2 44 1 7 00 3 7 46 IAS

The standard electrode potentials of Zn Ag and Cuare 0 76 0 80 and 0 34 volt respectively then Correct Answer A Ag can oxidies Zn and Cu B Ag can reduce Zn and Cu Your Answer C Zn can reduce Ag and Cu D Cu can oxidise Zn and Ag

Given E Zn 2 Zn K Cu NH3 4 2 4 10 1 0 34 V Cu 2 Cu 0 76 V Zn electrode 1 L 2 M ZnSO4 Answer the following Cu electrode 1 L 0 2 M CUSO4 61 The emf of cell at 200 K is Given 2 303 R 2 10 4 and assume that E values are independent on temperature a 1 7 V c 1 09 V 1 08 V d 1 10 V 62 When 1 mole NH3 added to cathode compartment then emf of cell is at 298K a 0 81 V c 1 1 V b 1 91 V d 0 72 V 63 At what conc of Cut2 emf of the cell will be zero a 298K and conc of Zn 2 is remaining same 110 x 10 37 h 1 19 x 10 20

9 t respectively 5 0 x 10 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 NaI and Na CrO4 A AgCl B AgBr D AgI C Ag CrO4

Given the standard electrode potentials Pb Pb 0 13 V Sn Sn 0 14 V Zn Zn 0 76 V Mg2 Mg 2 36 V The metal which has the strongest reducing power is Pb Sn Zn

0 Corrosion of iron is essentially an electrochemical phenomenon where the cell reactions are a Fe is oxidised to Fe2 and dissolved oxygen in water is reduced to OH 8 b Fe is oxidised to Fe3 and H O is reduced to 02 c Fe is oxidised to Fe2 and H O is reduced to 0 d Fe is oxidised to Fe and H O is reduced to 0

Design electrochemical cells in which each of the following reactions occurs 3 a Ce4 aq Fe aq Ce aq Fe aq b Ag aq Cl aq AgCl s c HgO s H g Hg 1 H O 1 In each case write the representation of the cell and the reactions at the two electrodes

For the following galvanic cell Ell 0 03 V at 25 C cell Pt s H g 1 atm H aq 1 M Ag aq 1 M Ag s Calculate the value of AG Ag aq Given 1 F 96500 C moi 2895 kl 28 95 kJ

The bond dissociation energies of X Y and XY are in the ratio of 1 0 5 1 AH for the formation of XY is 200 kJ mol 2018 The bond dissociation energy of X will be a 200 kJ mol b 100 kJ mol c 400 kJ mol d 800 kJ mol

ALLEN BEGINNER S BOX 1 01169 mmag Pre Medical Chemistry 123 1 The resistance of 1 N solution of CH COOH is 250 92 when measured in a cell of cell constant 1 15 cm The equivalent conductance will be 2 92 9 cm

Voltage of the cell Pt s H 1atm HOCN 10 M Ag 0 8M Ag s is 0 98V Calculate the Ka for HOCN Neglect H because of oxidation of H g Ag e Ag s E 0 8 V Given 2 303RT F 0 06

Standard EMF of a galvanic cell involving 2e transfer is found to be 0 591 V at 25 C Calculate equilibri constant for the cell reaction 1 2010 2 1020 3 10 200 4 20010

The K of Ag CrO AgCl AgBr and Agl are respectively 1 1 x 102 1 8 x 10 5 0 x 10 9 8 3 x 10 Which one of the following salts will precipitate last if AgNO solution is added to the solution containing equal moles of NaCl NaBr Nal and Na CrO 2015 a AgCl c Ag CrO b AgBr d Agl

Which reaction with the following value of AH AS at 400 K is spontaneous and endothermic a AH 48 kJ AS 135 J K b AH 48 kJ AS 135 J K c AH 48 kJ AS 135 J K d AH 48 kJ AS 135 J K

A current of 9 65 A is passed through the aqueous solution of NaCl using suitable electrodes fo 1000 s The amount of NaOH formed during electrolysis is 1 2 0 g 2 4 0 g 3 6 0 g 4 8 0 g 21

Molar conductances of BaCl H SO and HCl at infinite dilutions are x x and x respectively Equivalent conductance of BaSO at infinite dilution will be 1 1 X1 X2 X3 2 X X X 2 3 2 x x 2x 4 X x 2x 2

Calculate E for the following cell cell BEGINNER S BOX 2 Zn s Zn Ag Ag s E 1 0 04 V 2 1 56 V 0 76V E 0 80V Ag Ag 3 1 56 V 4 0 84 V

The ionization constant of a weak electrolyte is 25 x10 while the equivalent conductance of its 0 01 M solution is 19 6 S cm eq The equivalent conductance of the electrolyte at infinite dilution in S cm eq will be 1 39 2 2 78 4 3 392 4 196 0 21

Methane gas and steam in equimolar amounts are taken in a flask and sealed where the following equilibrium was established CH g H O v CO g 3H g 2H g CO g CH OH g K atm At equilibrium if partial pressure of CO g as found to be 0 5 atm and total pressure inside the flask was 5 atm then K of the first reaction is approximately A 3 5 atm B 7 5 atm C 10 5 atm D 12 5 atm

In an experiment m grams of a compound X gas liquid solid taken in a container is loaded balance as shown in figure I below In the presence of a magnetic field the pan with X is ei deflected upwards figure II or deflected downwards figure III depending on the compoun Identify the correct statement s 1 Balanced Magnetic field absent m X 11 Upward deflection Magnetic field present N magnet S A If X is H O I deflection of the pan is upwards B If X is K4 Fe CN 6 s deflection of the pan is upwards C If X is O g deflection of the pan is downwards D If X is C6H6 1 deflection of the pan is downwards III Downward deflection Magnetic field present N S

1 The reduction potential of hydrogen half cell will be negative if a p H 1 atm and H 2 0 M b p H 1 atm and H 1 0 M c p H 2 atm and H 1 0 M d p H 2 atm and H 2 0 M potentials for 7 17

We have taken a saturated solution of AgBr Ksp of AgBr is 12 x 10 14 Given 8x10 Smmol 1 20 7x10 Sm mol 1 20 Ap 6x10 5 m mor 20 Br NO3 If 10 7 mole of AgNO3 are added to 1 litre of this solution conductivity specific conductance of this solution is cx10 7 S m1 The val Answer

Find molar conductance of NH OH at infinite dilution Given A Ba OH 2 A Ba BaCl 2A NH C 1 251 5 sm mol 1 523 Sm mol 280 Sm mol 130 Sm mol 2 350 sm mol 1

7 Which statement a Conductance with dilution is not correct of an electrolytic solution increases of an electrolytic solution decreases c Specific conductance of an electrolytic solution decreases with dilution b Conductance with dilution d Equivalent conductance of an electrolytic solution increases with dilution highest

7 Standard free energies of formation in kJ mol at 298 K are 237 2 394 4 and 8 2 for H O CO2 g and pentanerespectively The value of E cell for the pentane oxygen fuel cell is a 1 0968 V c 1 968 V b 0 0968 V d 2 0968 V 2008