Electrochemistry Questions and Answers

hich of the following statement s is are correct In electrolysis the amount of mass deposited or liberated at an electrode is inversely proportional the amount of electricity passing through the electrolyte The object to be electroplated is taken as anode electrode When electric current is passed through copper sulphate solution copper gets deposited to the ectrode connected to the negative terminal of the battery and i only and s only m only

required for the titration 1 The compound Fe Fe CN molar mass 324 g mol was subjected to oxidation using KMnO in the acidic medium and the product mixture was found to contain Fe and NO along with the liberation of CO It was found that x g of Fe Fe CN was completely oxidised by 40 ml of 0 63 M KMnO4 The value of 100x to the nearest integer is 5 E

a What is electrolysis and State Faraday s laws of electrolysis Mar 14 Mar 15 T S b A solution of CuSO is electrolysed for 10 minutes with a current of 1 5 amperes What is the mass of copper deposited at the cathode Mar 14 Mar 15 T S A P

75 For the disproportionation reaction 2Cu aq Cu s Cu aq at 298 K In K where K is the equilibrium constant is x 10 Given Cut E 0 16 VE Cut Cu 0 52 V 0 025

The following cell has a potential of 0 55 V at 25 Pt s H 1 atm H M Cl 1 M Hg Cl s Hg 1 What is the pH of the solution in the anodic chamber E 0 28 V 1 457 Cl Hg Cl Hg 2 14 07 3 0 15 4 7 15

Calculate the equilibrium constant for the reaction 3Mg2 2Al 3Mg 2Al For Mg 2e Mg k E 2 363 For Al 3e Al k E 1 662 Cr solution is obtained by electrolysis of Cr solution In 500 mL of 0 15 M Cr solution how long would it take to reduce Cr to Cr using a current of 0 158 A The potential of the DKE MgA2 Mg2 9 62 x 10 M Mg ISE ion selective electrode Cell is 0 367V When the Mg2 solution in the cell is replaced with an unknown Mg2 solution the cell potential becomes 0 244 V What is the concentration of this Mg2 solution

For an electrode reaction Mn aq ne M s The electrode potential at any concentration measured with respect to standard hydrogen electrode can be represented by Nernst equation as E Mn M but concentration of solid M is taken as unity so we 1 have E M M RT In Mn E Mn M nF Q For given reaction of electrode Cl g 2e 2Cl aq Nernst equation is given as E In Mn M A Nernst equation is given as Only One Correct Answer Q For given reaction of electrode Cl g 2e 2Cl aq Ecl Cl EC Cl B Ecl Cl E IVI IVI C Ecl Cl EC1 C1 Cl g 2e 2Cl aq Only One Correct Answer Cl Cl C Ech Cl Nernst equation is given as A Ecl Cl EC1 Cl RT M nF Mn RT 2F Ecl cl D Ech c Ech c B EC Cl EC C 2 1 RT In RT CI RI In F Pcl2 RT Ecl ct In CI 2F In CI RT CI 1 In 2F PC12 TUL RT 2F In RT CI 1 In 2F PC12 CI PC12 CU 12 PC12 AVI

5 The following galvanic cell has a potential E of 0 98 V at 298 K Zn s ZnX4 0 010 M X 2 00 M Zn 2 00 M Zn s a Write the balanced equation for the cell reaction and calculate E

Copper sulphate solution 250 ml was electrolysed using a platinum anode and a copper cathode A constant current of 2 mA was passed for 16 minutes It was found that after electrolysis the absorbance of the solution was reduced to 50 of its original value Calculate the concentration of copper sulphate in the solution to begin with A B C D 7 95 x 10 5M 7 95 10 4M 7 95 10 M 7 95 10 2M

A gas mixture consisting of 50 mol ethane 1 and 50 mol n butane 2 at 400 K and 5 bar enters a compressor and leaves it at 600 K and 50 bar Calculate the enthalpy change in the compression process if the system obeys Redlich Kwong equation of state

Please use the values in the resources listed below instead of the textbook values The rate of the electron exchange reaction between naphthalene C10H8 and its anion radical C10H8 in an organic solvent is diffusion controlled C10H8 C10H8 C10H8 C10H8 The reaction is bimolecular and second order The rate constants are as follows T K 305 295 291 275 k 109 M 1 s 1 2 64 2 21 2 05 1 49 Calculate the values of Ea AH AS and AG at 295 K for the reaction Hint Rearrange the equation below and plot In k T versus 1 T k Teaso Re AH RT M m KBT h Ea Hot AS MAGO 1 kJ mol 1 kJ mol 1 J K 1 mol 1 kJ mol 1

The dissolution reactions of gold Au in 1M HNO and 1M aqua regia 1M HNO 1M HCI are given below Au s NO3 aq 4 H aq AU aq NO g 2 H 0 1 Au s NO3 aq 4H aq 4 Cl aq AuCl Reduction Half Reaction 3 Au 3e Au AuCl 3 e Au 4 Cl NO3 4H 3 e NO 2H O 2 H 0 2eH 2 H O 9 a Calculate E cell and Key for the dissolution of gold in 1M HNO under standard conditions 9 aq E V 1 36 1 00 0 96 1 NO g 2 H O n 2 Celalets Et and K for the dissolution of gold in aqua regia under standard conditions 3

The emf of the given cell is 0 46 V Pt H H PO4 0 4M HPO4 6 4 10 M M 0 81M M s 1 atm 1 Lsolution If E M 2 M 0 76 VI log 3 0 477 log 2 0 3010 and temperature is 25 C The pH of left compartment initially is

d Protein hydrolysate is to be assayed for aspartic acid Exactly 5 0 mg of aspartic acid having a specific activity of 0 46 mCi mg is added to the hydrolysate From the hydrolysate 0 21 mg of highly purified aspartic acid having a specific activity of 0 01 mCi mg can be isolated How much aspartic acid was present in the original hydrolysate fal Write the of Triti 3

In an electrolytic cell containing molten Cal2 Select one a Ca is deposited at the anode b Current flows from the cathode to the anode through the solution c Ca2 gains electrons d lodine is released as I e 12 is released at the cathode

The cell reaction for the Zn H cell is Zn s 2H aq Zn aq H g Standard cell potential is 0 76 V and the cell potential at 298K is 0 45 V Calculate the pH of the cell if Zn 1 0 M and PH 1 0 atm at equilibrium H

electrochemical cell Mg s Mg OH 2 s NaOH aq MgCl aq Mg s given that E for the reduction half cell reaction is 2 369 V and E for the oxidation side is 2 690 V at 298 15 K You can assume that the solutions are ideal Enter in your answer to 2 decimal places in units of x10 11 Your Answer E E Answer RT InQ X b b 4ac 2a Constants and Conversion Factors ax bx c 0 fxdx Data for H O Standard values all at 298 15 K PH O 3175 Pa at 298 15K AH H O 285 83 kJ mol T273 15 K 1 1 Arus H 6 008 kJ mol K 0 51 K kg mol Tap 373 15 K dr X R 8 314 J K mol 0 08206 L atm mol K 0 08314 L bar mol K N 6 022 x 1023 mol g 9 81 m s 1 Pa 1 kg m s 1 L 1 dm10 m 1 kJ 1000 J 1 atm 101325 Pa 1 01325 bar 760 Torr 1 atm 1 bar 10 Pa 100 kPa 1 L atm 101 325 J Inx e de dx F 96485 C mol 1J 1 kg m s Avap H 40 646 kJ mol K 1 86 K kg mol M 18 02 g mol

Brass an alloy of copper and zinc can be produced by simultaneously electroplating the two metals from a solution containing their 2 ions A 32 83 A current is applied to the brass If 78 82 of the total current is used to plate copper while the rest goes to plating zinc what is the mass percent of copper in the brass Record your answer with one decimal

Which is a redox reaction 2Cul 2Cul 1 NaCl AgNO3 AgCl NaNO3 NH4Cl NaOH NH3 NaCl H O Cr SO4 2 6KOH2Cr OH 3K SO

Q2 The resistance of a conductivity cell when filled with 0 02M KCI solution is 164 ohm at 298K However when filled with 0 05M AgNO3 solution its resistance is found it be 78 5 ohm If the specific conductivity of 0 02M KCI is 2 768 x10 ohm cm 1 Calculate A The specific conductivity L of 0 05M AgNO3 B The molar conductivity of AgNO3 Solution

Over voltage is result of O O O O Discharge of H ions at the electrode surface 1 point Neutralization of the charge of the ions or protons by electrons Combination of H atom to form H2 molecules O All of the above

is the movement of 1p charged surfaces with corresponding ions and H2O in the stationary liquid induced by an external field O Colloidal suspension O Emulsion O Micro emulsion

21 A particle is projected in the X Y plane with y axis along vertical 2 sec after projection the velocity of the particle makes an angle 45 with the X axis 4 sec after projection it moves horizontally Find the velocity of projection 1 10 5 m s 2 10 m s 3 20 m s 4 20 5 m s 60 20m s 457 10m 400x 25 50 39 28 2X25 x V 25 1 4 X Y Z 2 48e 40x2 800 800 h 2440 1 10 5 m s 2 10 m s 3 20 m s 4 20 ml 10 6 4 60 45 20m s 457 a f uxs3 BABARNANTY 10m 40560 u 8 20 CUS 20 XX 20 x2

0 For a cell A s A aq B aq B Ecell is 4 2 V at 25 C and 4 1V at 35 C The 0028 value of ASO for cell reaction assuming AS 6 in JK mol is 1 9 65 3 965 nda imited 0 05 2 96 5 4 0 965

Which one of the following statement is incorrect regarding the galvanic cell in which the reaction Zn s 2Ag aq Zn aq 2Ag s takes place 1 Zn is negatively charged electrode 2 Ag is negatively charged electrode 3 The flow of current is partly due to flow of electrons and partly due to flow of ions 4 Current Now from A to Zn in external

Given the standard electrode potential K K 2 93V Ag Ag 0 80 V Hg2 Hg 0 79V Mg Mg 2 37V Cr Cr 0 74V Correct order of their reducing power is 1 Ag Hg Cr Mg K 2 K Mg Cr Hg Ag 3 K Cr Mg Ag Hg 4 Cr Mg K Hg Aq

161 Given that Zn 1 2O ZnO 84000 Cal Hg 20 HgO 21700 Cal The heat of reaction AH for Zn HgO ZnO Hg is 1 105700 Cal 3 105700 Cal 2 62300 Cal 4 62300 Cal

Use the following table to find the standard reduction potential E Red for the half reactions listed below Given Zn 2e Zn E Red 0 76V E cell E Catho Measured voltages for galvanic cells using standard conditions Anode E V Zn Zn Cathode Cu Cu Cu Cu Bry Br Zn Zn Cl CI Ag Ag a Cl 2e 2 CI b Ag e Ag E Red E Red SHE Zn Zn K K Ag Ag K K 1 10 0 34 1 85 2 16 0 56 3 72

1 and Br are added to a solution containing 1M each off and Br ions Which of the following action will take place Given Standard reduction potentials of Land Br are 0 53 and 1 09 Volts repectively 1 lodine will reduce bromide ions 2 Bromine will reduce lodide ions 3 lodide ions will reduce bromine 4 Bromide ion will reduce lodine

The following galvanic cell has a potential of 1 21 V at 25 C Hg 1 Hg Br s Br 0 1 M MnO4 0 1 M Mn 0 1 M H 0 1 M Pt Calculate the solubility product Hg Br at 25 C Given E 2 Hg Hg 1 0 80 V E MnO4 H Mn 1 51 V

When a rod of metallic lead was added to a 0 01 M solution of Colen 3 it was found that 68 of the cobalt complex was reduced to Colen 32 by the lead Epb 2 Pb s 0 126 V AG of the reaction is A 10 34 kJ B 10 34 KJ

246 31 Pre Medical Chemistry The enthalpy of vaporisation of water at 100 C is 40 63 kJ mol The value AE for this process would 2 39 08 kJ mol be 1 37 53 kJ mol

3 A particle having a charge of 10 0 C and Q 83 10 0 g 10 1 cm 0 1 mass 1 g moves in a circle of radius 10 cm under the influence of a magnetic field of induction 0 1T When the particle is at a point P a uniform electric field is switched on so that the particle starts moving along the tangent with a uniform velocity The electric field is X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X XXX X px x X X X X X X X X 1 0 1 V m 3 10 0V m 2 1 0 V m 4 100 V m fag en forer a en at switched on fut e a X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X XX X X faga 1 0 1 V m 3 10 0V m X X X X X X X X 2 1 0 V m 4 100 V m Exams

2 130 The reduction potential of hydrogen electrode Q 130 25 C pOH 4 having pOH 4 at 25 C is 1 Zero volt 3 0 59 V 2 0 59 V 4 59 mV 1 3 0 59 V BIG C a 2 Med 2 0 59 V 4 59 mV

ALLEN 5 What is the potential of the cell containing two hydrogen electrodes as represented below Pt Halal H710 MILH 0 001 MTHolol Pr

ALLEN ELECTROLYSIS 62 When an electric current is passed through acidified water 112 mL of hydrogen gas at STP collects at the cathode in 965 s The current passed in ampere is 1 1 0 3 0 1 2 0 5 4 2 0

1 The standard electrode potential E for OCI C and Cl Cl respectively are 0 94 V an 1 36 V The E value of OCI Cl will be 1 2 20 V 2 0 42 V 3 0 52 V 4 1 04 V

59 The equilibrium constant in approx of the cell reaction Cu s 2Ag aq Cu 2 aq 2Ag s if E 0 465 V at 298 K is 1 2 0 1010 3 3 16 x 1015 2 3 16 x 1012 4 4 x 1010

4 decreases by EC0063 51 Which of the following will increase the voltage o the cell with following cell reaction Sn 2Ag Sn 2Ag 1 Increase in the size of silver rod 2 Increase in the concentration of Sn ions 3 Increase in the concentration of Ag ions 4 Decrease in the concentration of Ag ions

EC0067 55 The hydrogen electrode is dipped in a solution of pH 3 at 25 C The electrode potential of the half cell would be 1 0 177 V 3 0 087 V 2 0 177 V 4 0 059 V

7 Consider the cell Cul Cu2 Ag 1 Ag If the concentration of Cu and Ag lons becomes ten times then the emf of the cell will 1 Becomes 10 times 2 Remains same 3 Increases by 0 0295 V 4 Decreases by 0 0295 V

Consider the reaction Cl g 2Br aq 2C aq Br 0 The emf of the cell when CH Br 0 01 M and Cl gas at 0 25 atm pressure will be E for the above reaction is 0 29 V 1 0 54 V 2 0 272 V 3 0 29 V 4 0 29 V

EC0054 44 Which of the following represents the electrode potential of silver electrode dipped into 0 1 M AgNO solution at 25 C E 3 E 0 059 202 09 2 E 0 059 4 E 0 059

4 Cu can oxidise Zn and Ag EC0047 38 Standard reduction potentials of four metal electrodes are A 0 250 V C 0 126 V B 0 140 V D 0 402 V The metal that displaces A from aqueous solution of its compounds is 1 B 3 D 2 C 4 None of the abo EC0049 39 The following four colourless salt solutions are placed 44 Which potentia AgNO 3 E 107 45 The ele dipped 1 0 05 3 0 0

EC0051 41 On the basis of the following E values the strongest oxidizing agent is Fe CN Fe CN Fe Fe e 1 Fe 3 Fe CN E 0 35 V E 0 77 V 2 Fe CN 4 Fe EC0098 47 The st Zn The 0 1 M 25 C 1 1 1 3 1

as reduction occurs at anode in a galvanic cell EC0033 29 Other things being equal the life of a Daniell cell may be increased by 1 Keeping low temperature 2 Using large copper electrode 3 Decreasing concentration of copper ions 4 Using large zinc electrodes EC0034

Mg are 2 37 V ng is the 4 Mg EC0045 solution NERNST EQUATION 42 EXN Ni 0 25 V E Au Au 1 50 V The emf of the voltaic cell Ni Ni 1 0 M Au 1 1 25 V 1 0 M Au is 2 1 75 V

3 The emf of the cell Tl s ITI 0 0001 M Cu 0 01M Cu s is 0 83 V The emf of this cell will be increased by 1 Increasing the concentration of Cu2 ions 2 Decreasing the concentration of T 3 Increasing the concentration of both 4 1 2 both

2 Using the standard electrode potential values given below decide which of the statements I II III and IV are correct Choose the right answer from 1 2 3 and 4 Fe 2e Cu 2 E 0 44 V E 0 34 V Agi E 0 80 V Copper can displace iron from FeSO solution fron can displace copper from CuSO solution III Silver can displace copper from CuSO solution IV Iron can displace silver from AgNO solution 1 I and II 2 II and III 3 II and IV 4 I and IV Fe Cu 201

ALLEN 35 The standard reduction potential at 25 C of NE Li Li Ba Ba Na Na and Mg Mg are 3 05 V 2 73 V 2 71 V and 2 37 V 42 respectively Which one of the following is the strongest oxidising agent 1 Na 2 Li 3 Ba 4 Mg