Electrochemistry Questions and Answers

The cell Pt H g 1atm H pH x Normal electrode has EMF of 0 64 volt at 25 C The standard reduction potential of normal electrode is 0 28 V The anodic compartment has PH Take 2 303RT F 0 06 at 298 K A 4 B 5 C6 he

The conductance of a 0 0015 M aqueous solution of a weak monobasic acid was etermined by using a conductivity cell consisting of platinized Pt electrodes The distance etween the electrodes is 120 cm with an area of cross section of 1 cm The conductance f this solution was found to be 5x10 S The pH of the solution is 4 The value of miting molar conductivity A of this weak monobasic acid in aqueous solution is Zx10 S cm mol The value of Z is

69 In HS I R NH2 NH3 order of proton accepting tendency will be a I NH3 R NH HS b NH3 R NH HS c R NH NH3 HS d HS R NH NH3 F means Myhre basicit 2001

Molar conductivity of a weak electrolyte AB at 0 01 M concentration was found to be 10 S cm mol 1 What will be the molar conductivity of this electrolyte when concentration is 0 005 M The molar conductivity at infinite dilution is 400 S cm mor Assume the degree of dissociation is negligible as compared to unity 14 14 S cm mol 1 A B 28 28 S cm2 mol 1 C 40 S cm mol 1 D 100 S cm mol 1

How many moles of iron metal will be produced by passage of 4A of current through 1L 0 1 M Fe solution for 1 hour Assume only iron Fe 3 3e Fe is reduced B 0 2459 D 0 0521 A 0 0156 C 0 0245

3 Etard reaction 4 Williamson Synthesis 73 The anodic half cell of lead acid battery is recharged using electricity of 0 05 Faraday The amount of PbSO electrolyzed in g during the process is Molar mass of PbSO4 303 g mol 1 22 8 2 15 2 3 7 6 4 11 4

Consider the following information at 25 C AgBr s c Ag Br nq E AgBr s Ag 0 07333V Ag aq Ag s Ag aq Ag s 0 8496 V What is the value of the solubility product equilibrium constant Kap AgBr of silver bromide in aqueous solution at 25 C S AgBr s Ag Br 1 Kp AgBr

Construct galvanic cells for the given spontanet reactions i Zn s 2HCl aq ZnCl aq H g 1 atm ii Cl g latm 21 aq I s 2Cl aq iii H g latm Cl g 1atm HCl aq 2 iv Fe aq Ce aq Fe aq Ce aq v H g latm AgCl s Ag s HCl aq

A current of 2 50 A was passed through molten aluminum III oxide for 4 25 hours decomposing the compound into aluminum metal and oxygen p a Write the balanced electrode equations stating which reaction occurs at the anode and which occurs at the cathode 2 marks b Using your equations together with the data given calculate the mass of aluminum metal produced from this electrolysis process 2 marks

A silver electrode is immersed in a 0 1 M AgNO solution at 25 C If AgNO3 dissociates almos completely in the solution then determine the potential of the silver electrode 0 Ag Ag Given E 0 80 V

A certain boiler employs one hundred 2 cm diameter tubes 1 m long The boiler is designed to produce local forced convection boiling of water at 3 MPa pressure with ATX 10 C Estimate the total heat transfer rate and the amount of saturated vapor that can be produced at 3 MPa ww

A working electrochemical cell Ecell 0 is formed by zinc and silver electrode In this cell zinc electrode is dipped in 0 1 M ZnSO4 and silver electrode is dipped in 0 1 M AgNO3 solution as Om Zn If the emf of cell at 298 K is x Then the value of 100x to the nearest integer in V is 4 E22 Zn 0 76 V EO Ag Ag Ag 0 8 V

3 CaCO MgCO CaO MgO 2CO 4 2Cu S 30 2Cu O 2SO The logarithm of the equilibrium constant of the cell reaction corresponding to the cell aq Y s with standard cell potential E 1 2V is given by X s X aq 1 40 2 2 47 2 3 12 5 4 21 5

Conductivity of 0 1 M CH3COOH solution is measured in a conductivity cell that has cell constant 4 cm and resistance of 0 1 M CH3COOH solution is 1000 Q If molar conductivity of CH3COO and H at infinite dilution is x S cm mol 1 and 360 S cm mol 1 The value of x is If degree of dissociation of 0 1 M CH3COOH is 0 1

Consider the following electrochemical cell Zn Zn H H g Pt s 0 01 M x M 1 atm E Zn 2 Zn 0 77 V The E M F of cell at 25 C is equal to E cell The pH of solution in cathodic chamber is

Write the cell notation for standard cells based on the following reactions a the oxidation of silver by nitric acid assume that nitric acid is reduced to NO b Zn s 2Ag NH aq 2 2Ag s Zn NH aq

For the reaction 2Fe aq 21 aq 2Fe aq 1 s the magnitude of the standard molar free energy change 4 Gm kJ Round off to the Nearest Integer E Fe Fe s 0 440 V E E 12 21 0 539 V Fe s F 96500 C Fe 3 0 036 V

The net reaction catalyzed by malate dehydrogenase is malate NAD oxaloacetate NADH H The standard reduction potentials for the half reactions are given in the table Oxidant Reductant E V malate 0 17 NADH 0 32 oxaloacetate 2H NAD H Calculate AE for the given reaction AFY Calculate AG for the given reaction AG

After oper anode is removed then what will happen NCERT Pg 85 DD 1 The cell will work as a capacitor 2 lons will start moving randomly 3 Current will continue to flow for sometime 4 Cathode rod will start working as both anode and cathode

Calculate AG for the following cell reaction Zn s Ag O s H O I Zn aq 2Ag s 2OH aq 0 80 V and EZn 2 Zn 0 76 V F 96500 EAgt Ag Given Kp of AgOH 2 10 8 Option A B C D 305 kJ mol 212 kJ mol 305 kJ mol 301 kJ mol

Select the correct statements if 9 65 ampere current is passed for 1 hour through the cell Ag Ag Cu Cu IM IM A Ag will oxidise to Ag and new Ag 1 36 M B Agt will reduce to Ag and new Ag 0 64 M C Cu will reduce to Cu and new Cu 0 82 M D Cu will reduce to Cu and new Cu 1 0 82 M

436 0 kJ mol and 941 8 kJ mol respectively and nd dissociation enthalphies of H g and N g are enthalpy is of formation 46 kJ mol What is enthalpy of atomization of NH g 1 390 3 kJ mol 3 590 kJ mol 4 30 K cal mol 2 1170 9 kJ mol 4 720 kJ mol

58 Which one of the following graphs between molar conductivity A versus is correct 1 2 Am E KCI NaC1 3 KCI C NaCl KCI 19 NaCl

105 An electrochemical cell is set up as Pr s H H CH COOH 0 IM latm 0 1M H PI s 1 atm The emf of cell will not be zero because A the temperature is constant B emf depends on molarities of acids used C acids used in both half cells are different D pH values of both acid solution are not same

3 1 4 dihydroxy anthraquinone 4 1 hydroxyl anthraquinone 84 Given that E values of Ag Ag K K Mg Mg and Cr Cr are 0 80V 2 93V 2 37V and 0 74V respectively Therefore the order for the reducing power of the metal is 1 Ag Cr Mg K 2 Ag Cr Mg K 3 Ag Cr K Mg 85 Phosphate fertilizers when added to water leads to 4 Cr Ag Mg K

The overall formation constant of Co NH3 in aqueous solution is 10 at 298 K and the standard potential for reduction of Co aq and Co NH aq as follows Co aq eCo aq E 1 90V Co NH3 aq e Co NH aq E 0 IV If the overall formation constant of the Co NH3 ion is 10 at 298 K Then the 2 303RT value of x would be Given 0 06 F A 35 0 B 31 2 C 39 6 D 29 3

0 Two electrolytic cells containing AgNO3 abd CuSO4 solution connected in series A steady current of 2 5A was passed till 1 078g of Ag is deposited How long did the current flow What mass of copper will be deposited atomic mass of Ag 107 8 Cu 63 5

of MgCl is 240 S cm mol 1 A of Mg2 is 100 S cm mol 1 All above measurements are done in an conductivity cell Assuming MgCl to be a strong electrolyte which of the following is incorrect Question Type Multiple Correct Type 1 Limiting equivalent conductivity of MgCl2 is 480 S cm eq 2 of MgCl varies linearly with its concentration 3 of 0 04 M MgCl will be 160 S cm mol 1 4 of 0 04 M MgCl will be 200 S cm mol 1

If an electric current of 1 50 amps is passed through the cell used in question 17 for 40 0 minutes what would be the mass in grams of Cu s that is deposited on the electrode A 1 19 grams of Copper B 2 38 grams of Copper C 3 60 grams of Copper D 1 87 grams of Copper

86 What is the electrode potential of a gaseous hydrogen electrode dipped in a solution pH 5 0 relative to the calomel electrode with an electrode potential of 0 28 V 1 0 015 V 2 0 575 V 3 0 015 V 4 0 575 V

52 The rusting of iron takes place as follows 2H 2e O H O 1 E 1 23 V 2 Fe 2e 2e Fe s E 0 44 V AGO for the net process is 1 322 kJ mol 1 3 152 kJ mol 1 2 161 kJ mol 1 4 76 kJ mol 1

4 None of these 32 The value of molar conductivity of HCl is greater than that of NaCl at a particular temperature because 1 Molecular mass of HCl is less than that of NaCl 2 Velocity of H ions is more than that of Na ions 3 HCl is strongly acidic 4 Ionization of HCl is larger than that of NaCl

120 Given the following cell at 25 C H CH COOH NaOH H Pt 1 atm 10 M 10 3M 1 atm What will be the potential of the cell Given pk of CH3COOH 4 74 a 1 0 42 V 2 0 42 V Pt 3 0 19 V 4 0 19 V

39 10800 C of electricity passed through the electrolyte deposited 2 977 g of metal with atomic mass 106 4 g mol The charge on the metal cation is 1 4 2 3 Gal 11 3 2 ll the go 4 1 rion of iron be most

The H O fuel cell have cell reaction 2H2 g O2 g 2H O and cell potential 1 23 V The half cell O2 g 2H O 4e 40H aq has E 0 4 V then find E for 2H O 2e H g 2 H 1 0 41 V 2 0 83 V 3 0 41 V 4 0 83 V R PT X 742 78 X AG A

118 Given the standard potential of the following at 25 C E 0 95 V MnO Mn Mn3 Mn 1 51 V E The standard potential of MnO Mn is 2 obot t 1 0 56 V 2 2 46 V 3 1 23 V 4 1 23 V

K Cr O7 is the powerful oxidising agent in acidic medium In the same medium if oxidising powe of Cr O7 decreases by x volts when pH of the solution increases from 0 to 5 at 298 K then the value of 10x will be Take 2 303RT F 0 06

select the correct statement A Animal hides are colloidal in nature Emulsions can be diluted with any amount of the dispersion medium on the other hand disperse liquid when mixed forms a separate layer Emulsions do not show brownian motion and Tyndall effect For a colloid solution the values of colligative properties are of small order as compared to values shown by true solutions at same concentrations B C D

Consider the following electrochemical cell Cu2 Cul H H Pt to calculate the maximum activity of copper ions Cu2 in solution due to oxidation of a copper strip immersed in sulfuric acid H SO4 at 25 C 101 kPa and PH 2

122 Given electrode potentials are Fe e Fe 1 2e210 E for the cell reaction cell 2Fe 21 Fe 1 is 1 2 x 0 771 0 536 1 006 V 2 0 771 0 5 x 0 536 0 503 V 3 0 771 0 536 0 235 V mazum 4 0 536 0 771 0 236 V E 0 771 V E 0 536 V

For molar equivalent conductivity of a electrolyte A By which of the following is correct for kohlroush law Ox AG Av y Ag gr OX Am AY Y Am B 169 Av 6 Br X y Ox Am A y Am By

2 The cell diagram for an electrochemical cell is written as Ni s NiCl aq Ce ClO4 4 aq Ce CIO4 3 aq Pt s Write the equations for the half cell reactions that occur at the electrodes Balanc overall cell reaction

5 According to Kohlrausch law the limiting value of molar conductivity of an electrolyte A B is 1 2 A 200 A BO 1 A 2 3 2200 BO 2 20 A 2 BO 4 2200 BO A 200

Following data is obtained for aqueous solution of NaCl at 25 C conc M A ohm m mol Identify the correct statement s regarding the solution at 25 C A The value of m is 0 017 ohm m mol B The value of Am for 0 16 M NaCl solution is 0 0162 ohm m mol C The conductivity of 0 04 M NaCl solution is 0 664 ohmm when the conductivity of neglected 0 25 1 00 0 016 0 015 Conductivity of NaCl solution increases on dilution b

107 For the half cell OH Ope OH O 2H 2e E 1 30 V At pH 2 the electrode potential is 1 1 36 V 2 1 30 V 3 1 42 V 4 1 20 V

4 5 0 V 3 The reduction potential of hydrogen negative if 1 p H 1 atm and H 2 0 M 2 p H 1 atm and H 1 0 M 3 p H 2 atm and H 1 0 M 4 p H 2 atm and H 2 0 M Rac AIEEE 2010 half cell will be AIEEE 2011

2 101 Zn Cu aq Cu Zn aq Reaction quotient is Q Zn Cu Qis of the type with OA 1 10 cell V E will be 1 1591 V when 1 Cu Zn 0 01 2 Zn Cu 0 01 3 Zn Cu 0 1 4 Zn Cu 1 12 Cu e Cu E x Variation of Ecell with log A Ecell ol volt X volta banb Log Q

36 Total charge required for the oxidation of two moles Mn O into MnO2 in presence of alkaline medium is b 10 F a 5 F d None of these c 20 F 17 If E O 2 x V E Fe 23 Fe2 X V What 45 Ele the

5 The standard reduction potentials for Zn Zn Ni Ni and Fe2 Fe are 0 76 0 23 and 0 44 V respectively The reaction X Y2 Y will be spontaneous when 1 X Ni Y Fe 2 X Ni Y Zn 3 X Fe Y Zn 4 X Zn Y Ni LA FF 3013

Electrolysis of NaCl solution with inert electrodes for certai period of time gave 600 cm of 1 0 MNaOH in the electrolyt cell During the same period 31 80 g of copper was deposited in a copper voltameter in series with the electrolytic cell The percent current efficiency in the electrolytic cell is 20X Find the value of X At wt of Cu 63 6