Electrochemistry Questions and Answers

py change for one mole of an ideal gas in an isothermal process at 400 K is 2 8 Cal k mole Given In2 0 7 If process is carried out in a single stop then work done is 600 Cal If process is carried out in a single step then work dono is 1120 Cal Enthalpy is constant for the process If the above process is carried out in vacuum then entropy change is zero CODE

31 The emf of the ceil Pt H HA HC H Pt is 0 295 V Dissociation constant of the acid HA 0 01 M IM 1 atm 1 1x 104 3 1 x 10 2 1 x 10 6 4 1 x 10 5

a H b Na 25 A dilute aqueous solution of CuSO4 is electrolyzed using platinum electrodes The products at the anode and cathode are a O2 H2 c O 2 Cu d S 0 H b H 2 02

24 If Pt is used as cathode in the electrolysis of aqueous NaCl solution the ion reduced at cathode is a H b Na c OH d Cl luged using platinum electrodes The products a

Resistance of a conductivity cell filled with a solution of an electrolyte of concentration 0 1 M is 100 The conductivity of this solution is 1 29 S m Resistance of the same cell when filled with 0 02 M of the same solution is 520 2 The molar conductivity of 0 02 M solution of the electrolyte will be 1 124 x 10 4 S m mol 1 2 1240 x 10 4 S m mol 1 3 1 24 x 10 4 S m mol 1 4 12 4 x 10 4 S m mol

The ratio of number of moles of AgNO3 Pb NO and Fe NO required for coagulation of a defini amount of colloidal sol of silver iodide prepared by mixing AgNO with excess KI will be A 1 2 3 B 3 2 1 D 2 3 6 ired to protect 100 ml of gold sol f C 6 3 2 Joabe or

Which one of the following metals can not be obtained on electrolysis of aqueous solution of its salts a Mg d c Cu d Cr b Ag

12 The pressure of H required to make the potential of H electrode zero in pure water at 298 K is NEET 2016 1 104 atm 3 10 12 atm 2 10 14 atm 4 10 10 atm

One gm metal M weight of metal a 33 35 T was discharged by the passage of 1 81 x 1023 electrons What is the atomic b 133 4 c 66 7 d None of these MnO in presence of

Four moles of electrons were transferred from anode to cathode in an experiment on electrolysis of water The total volume of the two gases dry and at STP produced will be approximately in litres a 22 4 c 67 2 b 44 8 d 89 4

4 The electric charge required for electrode deposition of one gram equivalent of a substnace is b 96500 coulombs per second d charge on one mole of electrons a one ampere per second c one ampere for one hour 1

3 ber of Faradays F required to produce 20 g of calcium from molten CaCl Atomic mass of Ca 40 g mol 1 is CaCl 3 z t 9600 1 2 3 4 4 1 2 N 2 N 2 40 M1 20

Degree of dissociation of 0 1 N CH COOH is constant 1 x 10 5 2 10 4 3 10 4 10 2 Dissociation 1 10 5

red contained 0 1M MnO MnO 8H 5e Calculate the potential of an indicator electrode versus the standard hydrogen electrode which originally and 0 8M H and which was treated with Fe2 to reduce 90 of the MnO to Mn Mn H O E 1 51V Cal

If three Faradays F of electricity is passed through the solutions of AgNO3 CuSO4 and AuCl3 the molar ratio of the cations deposited at the cathode is a 1 1 1 b 1 2 3 c 3 2 1 d 6 3 2

Ethane gas is obtained in Koble s electrolysis of CH3COONa according to the following reaction CH3 2CH3COO 1 2CO 2e CH3 What volume of gas ethane gas at S T P would be obtained by a current of 0 5 amp 80 efficient if the current is passed for 965 min 1 1 8 L 2 2 688 L 4 11 2 L 3 5 45 L

Which of the following relation holds true for an equilibrium reaction if its reaction quotient Q 1 1 AG 0 2 AG 0 3 AG AGO 4 AG AG

26 By how much will the potential of half cell Cu 2 Cu change if the solution is diluted to 100 times at 298 K 1 Increases by 59 mV 2 Decreases by 59 mV 3 Increases by 29 5 mV 4 Decreases by 29 5 mV

Pure water is saturated with pure solid AgCl a silver electrode is placed in the solution and the potential is measured against normal calomel electrode at 25 C The experiment is then repeated with a saturated solution Agl If the difference in potential in the two cases is 0 177V What is the ratio of solubilities of AgCl and Agl at the temperature of the experiment a 10 c 10 b 106 d 104

and equilibrium constant of the reactions 5 Write the Nernst equation and emf of the following cells at 298 K i Mg s Mg2 0 00TM Cu 0 0001 M Cu s ii Fe s Fe 0 001M H 1M H g 1bar Pt s iii Sn s Sn 0 050 M H 0 020 M H g 1 bar Pt s iv Pt s Br l Br 0 010 M H 0 030 M H g 1 bar Pt s

4 ACE Aluminium oxide may be electrolysed at 1000 C to furnish aluminium metal Atomic mass 27 amu 1 Faraday 96 500 Coulombs The cathode reaction is Al 3e AP To prepare 5 12 kg of aluminium metal by this method would require 1 5 49 10 C of electricity 3 5 49 10 C of electricity Q mFZ M 2 1 83 10 C of electricity 4 5 49 10 C of electricity MAINS 2005

The enthalpy of formation of ammonia is 46 0 k mol The enthalpy change for the reaction 2 NH3 g 2 N2 g 3 H g is a 46 0 k mol 1 b 92 0 kJ mol 1

i Cu 2HCl CuCl H g E Cu Cu 0 34 V ii Zn 2IICI ZnCl H E Zn Zn 0 76 V iii Ag HCl AgCl H g 2 E Ag Ag Which of the above reactions is feasible 1 ii 3 iii 0 80 V 2 i 4 All

O an Ecell or A G for cell reaction ever be equal to zero

The conductivity of a solution which is 0 1 M in Ba NO3 2 and 0 2 M in AgNO3 is 5 3 Sm If Ag 6 x 10 3 Sm mol 1 Ba 13 x 10 3 Sm mol determine NO in same unit Report your answer after multiplying by 1000

positive value of the standard electrode potential o Cu Cu indicates that 201 a this redox couple is a stronger reducing agent than the H H couple b this redox couple is a stronger oxidising agent than H H c Cu can displace H from acid d Cu cannot displace H from acid 115 420

d None of these Calculate the potential of a half cell having reaction Ag S s 2e2Ag s S aq in a solution buffered at pH 3 and which is also saturated with 0 1 MH S aq Given Ksp Ag 25 10 49 K K 10 2 Ka a 1 18 b 0 19 The conductivity of 01 N NaOH solution 0 00 c 0 19 V 1 un d none of these

3 Equivalent conductances of Ba and Cl ions are 127 and 76 ohm cm eq respectively Equivalent conductance of BaCl at infinite dilution is a 139 5 c 203 b 101 5 d 279 2000

Which one of the following electrolytes will be most effective in coagulation of arsenoussulphide As2S3 sol a KCI b NaCl d AICI 3 c MgCl

Which of the following is incorrect about galvanic cell 1 Oxidation occurs at anode 2 reduction occurs at cathode 3 the electrode at which electrons are gained is called cathode 4 the electrode at which electrons are lost is called cathode

Same amount of current passed through two separate electrolytic cells containing FeCl3 and NISO4 solutions respectively if 112 g of Fe deposited in first cell then amount of Nickel deposited is molar mass of Fe 56 molar mass of Ni 59

9 A hydrogen gas electrode is made at 25 C by dipping platinum wire in aqueous HCI solution of pH 4 and by passing hydrogen gas at one atmosphere The reduction potential of the electrode at 25 C will be 1 0 118 V 3 0 059 V 2 0 236 V 4 0 118 V

8 Standard electrode potentials for Fe electrode are given Fe 2e Feils E 0 44 V E 0 77 V Fe e Fe2 brit b Fe Fe and Fe blocks are kept together then 5 a Fe decreases som b Fe increases 290 c Fe2 Fe remains unchanged d Fe decreases HT 5 sig ow I

Based on the cell representation for a spontaneous reaction at the anode Ag s AgCl s C1 aq Br aq Br l C s AgCl becomes reduced 2 Ag becomes oxidized 3 Br becomes oxidized reduced

4 moles of electrons were transferred from anode to cathode in an experiment on electrolysis of water The total volume of the pure gases at STP produced will be approximately 1 22 4 L 3 56 2 L 2 94 8 L 4 67 2 L

1 2 A big irregular shaped vessel contained water the conductivity of which was 2 56 x 10 5 S cm 500 g of NaCl was then added to the water and the conductivity after the addition o NaCl was found to be 3 10 x 105 S cm The capacity c the vessel if it is fulfilled with water A of NaCl 149 9 baris m 0 Hand Toil 105 litres or c 2467 5 x 102 litres d 2 3725 105 litres a 4587 9 102 litres b 3 4752 x

For which of these oxidation reduction pairs will the reduction potential vary with pH 4 II AmO2 Am I AmO AmO III Am Am 1 I only 3 I and II only 2 II only 4 I II and III

Considering the elements F Cl O and N the correct order of their chemical reactivity in terms of oxidizing property is a F Cl O N c Cl F O N b F O Cl N d O F N Cl

The specific conductance of a saturated AgCl solution is found to be 1 86 x 10 6 Scm and th for pure water is 6 0 x 10 8 S cm If for AgCl is 137 2 Scm eqvt the solubility of AgCl water would be A 1 7 x 103 M C 1 3 x 10 4 M B 1 3 x 10 5 M D 1 3 x 10 M A magnetic moment of 1 73 B M will be shown by one of the following compounds

6 The standard potentials at 25 C for the following half cell reactions are given as 2 Zn 2e Zn E 0 762 V esibi 2 Mg 2e Mg E 2 37 V cell When zinc dust is added to a solution of magnesium chloride A no reaction will take place B zinc chloride is formed C zinc dissolve in solution D magnesium is precipitated

1 Half cell reactions for some electrodes are given below 1 A e A E 0 96 V II B e B E 0 12 V III C e E 0 18 V IV D 2e D E 1 12 V Largest potential will be generated in which cell C 1 A A B B 3 B B C C 2 DD2 A A 4 DID 1 1C

The ionic conductance of Ba2 and Cl respec tively are 127 and 7692 cm at infinite dilution The equivalent conductance of BaCl at infinite dilution will be a 33052 cm c 13992 cm b 20352 cm d 512 cm

A direct current deposits 54 g of silver atomic mass 108 during the electrolysis The same quantity of electricity would deposit aluminium atomic mass 27 from aluminium chloride in molten state equal to 2 5 4 g 4 27 g 1 4 5 g 3 54 g

The conductivity of a saturated solution of CaF at 25 C is 6x 10S cm1 The conductivity of pure water is 2 10 S cm If for Ca2 and F ions are 72 and 64 S cm mol then K of CaF is m A 4 x 10 10 B 3 2 x 10 14 C 9 8 x 10 14 D 9 10 10

Small spherical ball of silver metal used in jewellery having diameter 0 1 cm which is obtained by the electrolytic deposition It total number of balls in jewellery is 10 000 then calculate the applied amount of electricity in coulombs which is used on the deposition on electrodes having entire surface 0 12 m Density of Ag 10 5 It is assumed that 3 5 electricity consumed as wastage during electrolysis and 60 of electrode body immersed in electrolyte Give your answer in multiple of 104

Specific conductivity of a solution a increases with dilution b decreases with dilution c remains unchanged with dilution d depends on mass of electrolyte cot

AH 298 2 kJ SO3 AH 98 7 kJ H SO4 AH 130 2 kJ H O AH 287 3 kJ If S O SO SO2 2 02 SO3 H O H 2 0 Then the enthalpy of formation of H2SO4 at 298 K will be a 814 4 k c 650 3 kJ b 320 5 kJ d 933 7 kJ

MnO 5e 8H Mn 4H O then Nerst equation for Epp is RP 1 E reaction 2 E 2 F MnO Mn MnO Mn E E 0 059 5 log 0 059 5 MnO H 2 log Mn2 Mn H O MnO4 Mn F 0 059x5log

12 The specific conductance of a saturated AgCl solu tion is found to be 1 86 x 106 S cm and that for water is 6 0 108 S cm The solubility of AgCl is Aq A 1372 S equiv cm eq A 1 7 x 103 mol L C 1 3 x 10 mol L A B 1 3 x 105 mol L 1 D 1 3 x 106 mol L L

8 By how much would the oxidizing power of the MnO Mn couple change if the H ions concentratio is decreased 100 times at 25 C A It will increase by 189 mV B It will decrease by 189 mV C It will increase by 19 mV D It will decrease by 19 mV