Electrochemistry Questions and Answers

El for some half cell reactions are given below On the basis of these mark the correct answer i H aq e H 8 Ell 0 00V ii 2H O 1 O g 4H aq 4e Eccell 1 23V iii 250 aq S O aq 2e Ecell 1 96V A In dilute sulphuric acid acid solution hydrogen ion will be reduced at cathode B In concentrated sulphuric acid solution water will be oxidized at anode C In dilute sulphuric acid solution water will be oxidized at anode D in dilute sulphuric acid solution So ion will be oxidized to tetrathionate iona

The Gibbs energy for the decomposition Al2O3 at 500 C is as follows Al O3 AI O 4 G 966 kJ The potential difference needed for electrolytic reduction of Al2O3 at 500 C is at least

Question Number 147 Question Id 8135612067 Question Type MCQ Display Questio Number Yes Is Question Mandatory No Single Line Question Option No Option Orientation Vertical If the concentrations of A B C at equilibrium in the reaction 3A B 2C D are 0 03 0 01 and 0 008 moles litre respectively calculate the initial concentrations of A B 3A B 2C D og Juodu 0 008 3rd bub Options 1 3056 A B eand A B e edo ou Cerddeu dur 0 03 0 01 mademu nodod A 0 042 M B 0 014 M 2 A 0 42 M B 0 014 M 3 A 0 042 M B 0 14 M

89 The reduction potential of silver electrode in Ag CrO 4 solution Ksp 4x solution at 25 C will be 0 80 V E EAgi Ag 1 0 80 2 0 80 3 0 80 0 0591 1 0 0591 1 0 0591 1 0 0591 log x log 2x log 2x Jog 2x

2 The reduction potential of a hydrogen electrode having pH value x and y atm pressure of H gas at 25 C is correctly given as 1 0 0591 logx y 2 2 0 0591 2x logy 3 0 0295 2x logy 4 0 0295 x logy

7 Molar conductances of Ca and Cl at infinite dilution are respectively x and x Equivalen conductance of CaCl at infinite dilution will be 1 X X 2 x x 2 3 X 2x 4 x 2x 2

Question Number 129 Question Id 8135611729 Question Type MCQ Display Question Number Yes Is Question Mandatory No Single Line Question Option No Option Orientation Vertical Find the electrode potential for given half cell reaction given below at pH 4 28 0 0 4H 4e E 1 23 V Given R 8 314 J K mol Temperature 298 K Oxygen is under standard atmospheric pressure of 1 bar 2H 0 0 4H 4e Ered 1 23 V Jod dgroddw R 8 314J K mol son bass 1 and 3 Options 1 1 53 V 2 0 99 V 3 1 01 V 1 23 V os pH 45g des Ja od 298 K an

800 d5 4 555 A Potential of Hydrogen electrode at pH 10 B Cu Cu C Zn Zn D 2 303 RT F an Do I A pH 10 5125 Jos B Cu Cu C Zn Zn2 2 303 RT D F The correct answer is 30555555 A B C D 1 III 1 II V 2 V 1 IV 3 III IV 1 II 4 VY avy an 1 0 76 V II 0 059 III 0 591 V IV 0 337 V V 0 76 V ar Der 11 1 0 76 V II 0 059 III 0 591 V IV 0 337 V V 0 76 V

Consider two reactions XY AG 386 KJ mol M 2e E p V M It is given that all the energy released from th conversion of X to Y is used in the oxidation of M to M4 Under standard conditions on conversion a 1 mole of X 4 moles of M are oxidised The value of 100p is use F 96500 C mol

A current of 3 ampere has to be passed through a solution of AgNO3 solution to coat a metal surface of 80 cm with 0 005 mm thick layer for a duration of approximately y seconds What is the value of y Density of Ag is 10 5 g cm

2 2x i Question Number 145 Question Id 7512365585 Question Type MCQ Option Shuffling Yes Display Question Number Yes Single Line Question Option No Option Orientation Vertical 1 3 Options 10 Consider the electrochemical reaction between Ag s and Cl electrodes in 1 litre of 0 1 MKCl aqueous solution Solubility product of AgCl is 1 8 1010 and F 96500 C mol When a current of 10 A is passed calculate the minimum time in seconds s required to observe the AgCl precipitation in the galvanic cell 1 565 0 1 M KCleo Ag 360oo AgCloer og So AgCles 38 0 o y 346 174 17 1 Chr g dog diri dag o 1 8x10 100F 96500 C mol 10 A o te Dojders say so odo s

EFe Fe 0 44 V The emf generated by the reaction 2 Cr 3Fe 2 Cr 3Fe when Cr 0 01 M and Fe2 0 1 M is Only one correct answer A 0 31 V B 0 29 V C 0 32 V

2Fe aq 21 aq 2Fe aq 1 aq E 0 24V at 298 K The standard Gibbs energy AG of the cell reaction is Given that Faraday constant F 96500 C mol 1 46 32 kJ mol 1 2 23 16 kJ mol 3 46 32 kJ mol 1

In each row check off the boxes that apply to the highlighted reactant reaction 3 3 Fe aq 6H O 1 Fe H 0 a Ni s 4 CO g Ni CO 40 2H O 0 2H O 1 O 9 The highlighted reactant acts as a check all that apply 0000000 Br nsted Lowry acid Br nsted Lowry base Lewis acid Lewis base Bransted Lowry acid Bransted Lowry base Lewis acid Lewis base Bransted Lowry acid Bransted Lowry base Lewis acid Lewis base

A 71 48 amp C 35 74 amp In a Cu voltameter mass deposited in 30 seconds is 100 grams Carefully analyse the current time graph shown below and identify the incorrect statement 100 mA 10s 20s 30s A electrochemical equivalent for Cu is 50 B a constant current of 66 66 mA would also discharge the same amount in the same time C 33 33 grams got discharged in 10 seconds 50 grams got discharged in 15 seconds

For an electrolytic cell experiment which will contribute to the greatest source of error on the mass of the deposited metal Select one A The experiment was done at a lower temperature B The electrolyte solution was more concentrated than the reported concentration C A lower voltage was applied in the electrolyte solution D The electrodes were not pre weighed and were weighed after the deposited metal was removed

0 5 Normal solution of a salt placed between two platinum electrodes 20 cm apart and of area of cross section 4 cm has a resistance of 25 ohm Calculate the equivalent conductance of the solution 1 0 2 ohm cm eq 1 2 200 ohm cm eq 3 400 ohm cm eq OT ON POCO 4 10 000 ohm cm eq T 12

The reversible reduction potential of pure water is 0 414V under 1 00 atm H pressure If the reduction is considered to be 2H 2e H Calculate the hydrogen ion concentration of pure water If Answer is x 10 7M then the value of x

e 3 Consider the change in oxidation state of Brom corresponding to different emf values as shown in 2018 the diagram below BrO 1 82 V BrO 1 5 1 5 V Br Br 1 0652 V Then the species undergoing a Bro b Bro HBrO 1 595 V disproportionation is d Br c HBrO

1 3 faraday of electricity is passed through molten Al2O3 aqueous solution of CuSO4 and molten NaCl taken in three different electrolytic cells The amount of Al Cu and Na deposited at the cathodes will be in the ratio of BHU 1990 a 1 mole 2 mole 3 mole b 3 mole 2 mole 1 mole c 1 mole 1 5 mole 3 mole d 1 5 mole 2 mole 3 mole

Hydrogen electrode is prepared by using 1L of aqueous solution containing 0 49 mg of H SO4 The oxidation electrode potential of that hydrogen electrode is A 0 3 V B 0 295 V C 0 295 V D Zero

at 2981 Fe CN 6 12 Standard free energies of formation in kJ mol a are 237 2 394 4 and 8 2 for H O CO2 8 AIPMT 2009 pentane g respectively The value of E cell for t pentane oxygen fuel cell is a 2 0968 V c 0 0968 V b 1 0968 V d 1 968 V

6 On electrolysis of aqueous solution of a halide of a metal M by passing 1 5 ampere current for 10 minutes deposits 0 2938 g of metal If the atomic mass of the metal is 63 gm mole then what will be the formula of the metal halide A MCL C MCI B MC1 D MC14

E for stoichiometric quantities of reactants at equivalent point of a titration is given by nE n E2 E M N Equation above was derived using two half reactions with equal n values Derived a similar equation for the following reaction using the numerical n values F Sn iti

c 4 0 10 5 11 On the basis of the following E values the oxidizing agent is Fe CN 6 Fe a Fe 2 c Fe CN 6 9200 3 11 Fe CN 6 e Fe e 3 stronge JAIPMT 200 E 0 35 E 0 77 b Fe 3 d Fe CN 6 14

The time required approx to remove electrolytically one half from 0 2 litres of 1M AgNO3 solution by a current of 1 amp is 1 320min 2 80min 3 160min 4 40min

13 The electrode potential of hydrogen electrode is when H O iom concentration is 10 5 M pH 1 atm O NCERT Pg 68 River 1 0 059 V 2 0 295 V 2645 0 118 V 4 0 59 V 14 3529 25 0 053 n 2 5 deqz 11 1 0 0 2 S 0 0124 K 100 0 3 257 4728

In the industrial chlor alkali process pure chlorine and sodium hydroxide are produced by electrolyzing brine essentially an aqueous solution of sodium chloride Suppose a current of 95 0 A is passed through an aqueous solution of NaCl for 81 0 seconds Calculate the mass of pures chlorine produced Round your answer to 3 significant digits Also be sure your answer contains a unit symbol

Calculate the magnitude of the current in amperes if the number of moles of hydrogen gas produced is 5 39x104 mol from part A Express your answer to three significant figures and include the appropriate units

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

Passage IV Tollen s reagent is used for the detection of aldehydes When a solution of AgNO is added to glucose with NH OH then gluconic acid is formed Ag eAg Ered 0 80 V C6H12O6 H O C6H 2O 2H 2e Gluconic acid Ag NH3 e Ag s 2NH3 RT Use 2 303 x 0 0592 and F RT Ex 0 05 V Ered 0 337 V 38 92 at 298 K 2006 3 x 4M 12M 32 2Ag C6H 2O6 H O2Ag s C6H 2O7 2H Find In K of this reaction a 66 13 0 58 38 c 28 30 d 46 29 33 When ammonia is added to the solution pH is raised to 11 Which half cell reaction is affected by pH and by how much a Foxi will increase by a factor of 0 65 from E b Exi will decrease by a factor of 0 65 from E c Ered will increase by a factor of 0 65 from E d Ered will decrease by a factor of 0 65 from Ered oxi oxi 34 Ammonia is always added in this reaction Which of the following must be incorrect a NH combines with Ag to form a complex Ag NH3 is a stronger oxidising reagent than Ag c In the absence of NH3 silver salt of gluconic acid is formed d NH has affected the standard reduction potential of glucose gluconic acid electrode

0 5 N solution of a salt placed between two platinum electrodes 20 cm apart and of area of cross section 4 cm has a resistance of 25 ohm Calculate the equivalent conductance of the solution Question Type Single Correct Type 1 0 2 ohm1 cm eq 1 2 200 ohm 1 cm eq 3 400 ohm 1 cm eq 1 o 1 2 1

5 Three moles of electrons are passed through three solutions in succession containing AgNO CuSO and AuCl respectively The molar ratio of amounts of cations reduced at cathode will be 1 1 2 3 2 2 1 3 4 6 3 2

4 Three faradays of electricity was passed through an aqueous solution of iron II bromide The mass of iron metal at mass 56 deposited at the cathode is 1 56 g 112 g 2 84 g 4 168 g

A 4 0 molar aqueous solution of NaCl of prepared and 500 mL of this solution is electrolysed This leads to the evolution of chlorine gas at one of the electrodes atomic masses Na 23 Hg 200 1 Faraday 96500 coulombs The total number of moles of chlorine gas evolved is 1 0 5 2 1 0 3 2 0 4 3 0 LIT

The product of oxidation of I with MnO in alkaline medium is 1 10 2 1 3 10 If E 0 44V E The 0 77V value of Er is 1 0 33 V 2 0 0367V 3 0 11 V 4 10 4 0 11V

Electrolysis of hot aqueous solution of NaCl gives NaClO4 Then the number of Faraday required to deposit 500 g of NaCIO4 is Molar mass of Na 23 g mol 1 Cl 35 5 g mol 1 0 16 g mol Your Answer 0 245 Rate this question

108g of silver molar mass 108g mol is deposited at cathode from AgNO3 aq solution by a certain quantity of electricity The volume in L of oxygen gas produced at 273K and 1 bar pressure from water by the same quantity of electricity is 1 2 82 L 2 5 675 L 3 1 41 L According to the following diagram a reduces BO when the temperature is 4 0 746L

c d All of the above 90 Which graph correctly correlates Ecell as a function of concentrations for the cell for different values of M and a M Zn s Cu2 M X axis log10 from 1 10V 1 0 0 1 0 1 10 V 1 0 0 1 0 Zn2 M Cu s ECell 1 10 V Zn2 Cu2 Y axis ECell b d 1 10V 1 0 0 1 0 1 10V 1 0 0 1 0

The bottom surface of a cylindrical furnace has an electric heating element that produces a constant heat flux of 7 kW m over a diameter of 75 cm The sidewalls are 50 cm high and may be considered as nonconducting and re radiating The bottom has 0 8 Over the top is placed a surface with 0 6 that is maintained at 400 K Determine the temperature of the bottom and side surfaces

Answer C D Calculate AG for the following cell reaction Zn s Ag O s H O I Zn aq 2Ag s EAg Ag 0 80 V and En 2 Zn 0 76 V F 9650 Given Kp of AgOH 2 x 10 8 B A Your Attempt 305 kJ mol 212 kJ mol 305 kJ mol 301 kJ mol Correct answer

27 If 9 g of H O is electrolysed completely with 50 current efficiency 1 1 F of electricity will be needed 2 3 F of electricity is needed 3 5 6 L of O at STP will be formed 4 11 2 L of O at STP will be formed

of these 18 E for Fe2 2e Fe is 0 44 volt and E for 2 Zn 2e Zn is 0 76 volt thus a Zn is more electropositive than Fe b Fe is more electropositive than Zn c Zn is more electronegative d none of the above potential

Tuoro 92 The main function of the salt bridge is a to allow ions to go from one cell to another b to provide link between two half cells c to keep the e m f of the cell positive d to maintain electrical neutrality of the solution in two half cells

a CuCl2 is precipitate AgCl is precipitated d all of 23 The calomel electrode is reversible with respect to 2 a Hg c Hg 2 b H d CI potential of an element is equal to

16 Which 2 ctrode d not at all defines the standard reduction electrode ions potential of Zn 2 a Zn aq 2e Zn s 2 Zn Zn 2e aq Zn s 2e Zn s 2e b Zn g c Zn2 2 d Zn g g n Zn 1M 2 Zn 1M ROV 2 Zn 1M 2 Zn 1M is converted

The limiting molar conductivities A for NaCl KBr and KCl are 126 152 and 150 Scm mol respectively The A for NaBr is 1 278 Scm mol 2 178 5cm mol 3 128 Scm mot 4 306 Scm mol

a doubles c remains same d beco 27 Copper can be deposited from acidified copper sulph and alkaline cuprous cyanide If the same current is passed for a definite time a the mass of copper deposited from acidic copper sulphate will be higher the mass of copper deposited from alkaline cuprous cyanide will be higher c the same mass of copper will be deposited d none of the above som ar

A solution contains Fe Fe and I ions This solution is treated with iodine at 25 C The possible 0 536 V redox reaction will be E Fe Fe 0 770 V and E I 21 A 1 will be reduced to I C I will be oxidized to I B There will be no redox reaction D Fet will be oxidized to Fe 4 25 C usaua m k akiva k Fe Fe fa a 20I YOKI GKA Gka Att 3 E Fe Fe 0 770 V and E I 21 0 536 V A 1 GRU 2 IR B C ISO 23 12 264 D Fe 23 Fe 264 G GKA RUBIK

7 8 The standard e m f of a cell involving one electron change is found to be 0 591V at 25 C The equilibrium constant of the reaction is F 96500 Cmol R 8 314 JK mol 1 1 0x 10 2 1 0x10 3 3 1 0 x 105 4 1 0x10 The enthalpies of combustion of carbon and carbon monoxide are 393 5and 283k Imol