electro chemistry assignment for iitjee.pdf

8/14/2019 electro chemistry assignment for iitjee.pdf

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RI CHAITANYA IIT ACADEMY - V P

SUB : CHEMISTRY DATE:

1. Which of the following half-reactions is involved in the STANDARD HYDROGEN ELECTRODE?

A)2

( ) ( )2aq s Pt e Pt

B) 3 ( ) 2 2( )( )2 2 2aq g l H O e H O H

C)

2 2( ) 3 ( ) 2 ( )2 2 4

aq aq l H O H O e H O

D) 2( ) 2 ( ) ( )2 4 4 g l aqO H O e OH

2. Suppose that gold is being plated onto another metal in a electrolytic cell. The half-cell reaction producing the Au(s) is

4 ( ) 4 3 s AuCl Au Cl e

If a 0.30 amp current runs for 15.00 minutes, what mass of Au(s) will be plated, assuming all the electrons are used in the

reduction of 4 AuCl ? The Faraday constant is 96485 /coul mole and molar mass of Au is 197.

A) 0.184 g Au B) 0.551 g Au C) 1.84 g Au D) 0.613 g Au

3. Consider a spontaneously operating electrochemical cell in which the net oxidation – reduction reaction is

3 4( ) ( )3 4 3 4 . s s Zr Fe Zr Fe Choose the statement which is false.

A) The anode reaction is4

4 Zr Zr e

B) The cathode reaction is3 3 Fe e Fe

C) Electrons flow from the cathode to the anode.

D) The standard potential for this cell will be > 0.

4. Which of the following statements is (are) true about electrochemistry?

I. The greater the electro negativity value the more the element wants to get rid of electrons.

II. If the cell potential is positive, then the electrochemical reaction is spontaneous.



III. The amount of material plated out in an electrochemical cell is related to the number of electrons that pass through the

cell.

A) I and II only B) II only C) III only D) II and III only

5. Which of the following best explains why concentration cells must be run under non-standard conditions in order for them to

do electrical work?

A) A concentration cell can only do electrical work when either 3 NH or NaOH is added to one of the half-cells.

B) A concentration cell cannot do electrical work at 25°C.

C) The change in free energy for a concentration cell is always negative under standard conditions.

D) A concentration cell has a cell potential equal to zero under standard conditions.

6. Which of the following statements about a salt bridge in a voltaic cell is TRUE?

A) Free electrons flow through the salt bridge to maintain electrical neutrality in the two half-cells.

B) The salt bridge allows the ions present in the two half-cells to mix extensively.

C) The wire must be connected directly to the salt bridge in order for the salt bridge to the able to maintain electrical

neutrality in the two half-cells.

D) Ions from the electrolyte in the salt bridge flow into each half-cell to maintain electrical neutrality.

7. Which of the following reactions can be used to construct a voltaic cell?

A) 3 ( ) ( ) 2 ( )2aq aq l H O OH H O

B) ( ) 2 ( ) 3 ( ) ( ) g l aq aq HF H O H O F

C)2 2

( ) ( ) ( )44aq aq aqCu F CuF

D) 2( ) 3 ( ) ( ) 2( ) 2 ( )4 4 2 6 g aq aq aq l O H O I I H O

8. Consider the following standard reduction potentials :

Half reaction (V)

2 ( ) ( )2aq s Ni e Ni

0.23 E V

2( ) ( )2aq s Fe e Fe

0.41 E V

2( ) ( )2aq s Mn e Mn 1.03 E V

2( ) ( )2aq sCo e Co 0.28 E V



3( ) ( )3aq sCr e Cr

0.74 E V

Which of the following metals could be used successfully to galvanize steel?

A) Ni only B) Ni and Co C) Fe only D) Mn and Cr

9. You know that silver tarnish 2[ ( )] Ag S s can be converted to silver metal ( ( )) Ag s by placing the tarnished silver piece

in a dilute solution of baking soda contained in an aluminium pan. The following half-reactions are thought to be involved,

( ) 3 ( ) ( ) 2 ( ) 2 ( )2

3( ) ( )

2 2 2 2

3

s aq s g l

aq s

Ag S H O e Ag H S H O

Al e Al

Which of the following statements is true?

A) As the silver piece is being cleaned, 3 H O

ions are produced and 2 H S gas is consumed.

B) It is necessary that the silver piece and the aluminium pan touch so that electrons can be transferred.

C) As the silver piece is being cleaned,3

Al

ions in the solution are reduced to Al metal.

D) The silver piece being cleaned functions as the anode.

10. In the Standard Hydrogen Electrode, a platinum wire is used as the electrode. Consider the following standard reduction

potentials,

2( )2 ; 0.76 s Zn e Zn E V

3 ( ) 2 ( ) 2( )2 2 2 ; 0.76aq l g H O e H O H E V

2( ) ( )2 ; 0.76aq s Pt e Pt E V

Which of the following statements best describes what would happen if the platinum wire in the Standard Hydrogen

Electrode were replaced with a zinc wire?

Note : Assume that this is the only change made to the half-cell.

A) Zinc ion in the solution would be reduced; the mass of the zinc electrode would increase.

B) The pH of the solution would decrease.

C) The zinc electrode would be oxidized; the mass of the zinc electrode would decrease.

D) This change would have no effect – the Standard Hydrogen Electrode would continue to function properly.

11. Which of the following statements best describes what will happen when magnesium metal is added to an aqueous solution

containing 1.0M ferric ion3( ) Fe

at 25°C?



2( ) ( )2 ; 2.375aq s Mg e Mg E V

3( ) ( )3 ; 0.036aq s Fe e Fe E V

A) ( ) s Mg will be oxidized;3

( )aq Fe will be reduced; the standard cell potential will be 2.339V.

B) ( ) s Mg will be oxidized;3

( )aq Fe will be reduced; the standard cell potential will be -2.339V.

C)3

( )aq Fe

will be oxidized; ( ) s Mg will be reduced; the standard cell potential will be -2.339V.

D)3

( )aq Fe will be oxidized; ( ) s Mg will be reduced; the standard cell potential will be 2.339V.

12. Suppose you have been given the task of selecting a metal to be used as the sacrificial anode for the cathodic protection of a

buried iron fuel tank. Considering the following standard reduction potentials,

2( ) ( )2 ; 0.99aq s Pd e Pd E V

2( ) ( ); 0.80aq s Ag e Ag E V

2( ) ( )2 ; 0.34aq sCu e Cu E V

2( ) ( )2 ; 0.23aq s Ni e Ni E V

2( ) ( )2 ; 0.41aq s Fe e Fe E V

Which of the following metals could be use as the sacrificial anode in this application?

A) Pd B) Ag C) Cu D) Ni

13. The cell potential for the electrochemical reaction shown below depends upon the Cl and2Cu

concentrations.

Calculate the cell potential (in V) at2

25 [ ] 3.5 [ ] 1.7 .C if Cu M and Cl M

2( ) ( ) ( ) ( ) ( )2 2 2 ; 0.12aq aq s s sCu Cl Ag Cu AgCl E V

A) 0.15V B) -0.15V C) 0.30V D) -0.30V

14. Consider the following reaction and standard cell potential

22( ) 3( ) 3 6 ( )

6 ( ) 0.25aq aq aq Ni NH Ni NH E V



Which of the following best describes what would happen in a solution that initially contains2

31.0 , 0.01 M Ni M NH

and 23 66.0 ( ) M Ni NH

at 25°C? (Assume that the number of moles of electrons transported in this reaction is

equal to 2.)

A) The concentrations of both2

Ni

and 3 NH would decrease and the concentration of 23 6( ) Ni NH

would

increase.

B) The concentrations of both2 Ni

and 3 NH would increase and the concentration of2

3 6( ) Ni NH would

decrease.

C) The concentration of 23 6( ) Ni NH

would decrease, the concentration of 3 NH would increase and the

concentration of2 Ni

would remain the same.

D) The concentrations of

2

Ni

, 3 NH and 2

3 6( ) Ni NH

would all remain the same.

15. Consider the following standard reduction potentials

22 ; 0.41 Fe e Fe E V

; 0.80 Ag e Ag E V

2 22 4 4 ; 0.40O H O e OH E V

Which of the following statements best describes what would happen if a block of silver metal were connected to a buried

iron pipe via a wire?

A) The silver metal would corrode, a current would be produced in the wire, and 2O would be reduced on the surface of the

iron pipe.

B) The silver metal would corrode, a current would be produced in the wire, and2

Fe

would be reduced on the surface of

the iron pipe.

C) The iron pipe would corrode, a current would be produced in the wire, and Ag would be reduced on the surface of the

silver metal.

D) The iron pipe would corrode, no current would be produced in the wire, and 2O would be reduced on the surface of the

iron pipe.

Passage: Use the following information to answer the question no 16,17,18



A galvanic cell is constructed from a half-cell containing a solid chromium electrode in 1.0 M 3 3( )Cr NO solution and

a half-cell containing a solid tin electrode in 1.0M 3 2( )Sn NO solution. The half-cell are linked by an external circuit

and by a KCl salt bridge.

2 2 ; 0.14Sn e Sn E

3 3 ; 0.74Cr e Cr E

16. The balanced overall (net) cell reaction is

A)3 2

( ) ( ) ( ) ( ) s aq aq sSn Cr Sn Cr

B)3 2

( ) ( ) ( ) ( )3 2 3 2 s aq aq sSn Cr Sn Cr

C)2 3

( ) ( ) ( ) ( )3 2 3 2aq s s aqSn Cr Sn Cr

D)2 3

( ) ( ) ( ) ( )aq s s aqSn Cr Sn Cr

17. Which of the following statements is true about this cell?

A) The chromium electrode is the anode; the lead electrode is the cathode.

B) The electrons flow from the tin electrode to the chromium electrode.

C) The cell diagram is2

| | ,1.0 |Sn solid Sn M

salt bridge 3

| | ,1.0 |Cr solid Cr M

.

D) H is the driving force of this reaction.

18. The value of the equilibrium constant at 25 C for this reaction is closest to

A)661.0 10 B)

436.7 10 C)17.4 10 D)

617.7 10

19. A metal bucket is to be galvanized by plating the bucket by an electrolytic procedure using aqueous 2 ZnCl as the

electrolyte. How many moles of zinc are deposited in 20.0 min by a constant current of 10 A ?

A) 0.01 B) 0.03 C) 0.06 D) 0.10

20. Which of the following is not a use of a galvanic cell?

A) Calculate values for standard free energy change.

B) Determine the order of a half – cell reaction.

C) Calculate E° of a half – cell reaction.

D) Determine the value of sp K for a salt.



21. An electrolysis plant processes sea – water to obtain Mg (s). If the plant operates its electrolytic cells at a total current of

61.0 10 A for 2.2 hrs, how many moles of Mg(s) will be produced from sea – water containing 2 Mg

?

A)4

4.10 10 moles B)9

7.92 10 moles C)4

9.64 10 moles D)4

8.20 10 moles

22. Which of the following is most likely TRUE for a ‘dead battery’?

A) 0 0cell G and E B) 0 0cell G and E

C) 0 0cell G and E D) 0 0cell G and E

Passage: Use the table of standard reduction potentials at 25°C below to answer the next five questions.

Half reaction E°,V

2 2Ca e Ca -2.87

Ag e Ag

+0.80

2 2 Zn e Zn -0.76

3 24 3 ( ) 2 NO H e NO g H O +0.96

2 2Sn e Sn -0.14

3 3 Au e Au +1.50

23. The strongest oxidizing agent on this list is

A)2Ca

B)3 Au

C) Au D) H

24. The strongest reducing agent on this list is

A)2

Ca

B) Ca C)3

Au

D) Au

25. Which of the oxidizing agents on the above list can oxidize Au to3 Au

at standard conditions ?

A) 3 NO in the presence of acid

B)2

Ca

C) All of the oxidizing agents with positive half – cell potentials for the reduction half reaction.

D) None of these oxidizing agents

26. What is the cell potential at 25°C for the reaction, 3 23 ( ) 4 3 ( ) 2 Ag s NO H Ag NO g H O



When 3[ ] 2.0 ,[ ] 0.010 , NO M Ag M pH is 1.00, and the pressure of NO is 0.20 atm?

A) 0.10V B) 0.16V C) 0.22V D) 0.30V

27. A concentration cell is made up of the2/ Fe Fe

couple, where the2 Fe

concentrations are 1.0M and 0.10M. Which

of the following statements best describes the operation of this cell?

A) The anode compartment contains a2/ 0.10 Fe M Fe solution, which decreases in concentration as the cell

operates, and the cathode compartment contains a2

1.0 M Fe solution which also decreases in concentration as the cell

operates.

B) The anode compartment contains a2

0.10 M Fe

solution, which increases in concentration as the cell operates, and

the cathode compartment contains a21.0 M Fe

solution which decreases n concentration as the cell operates.

C) The anode compartment contains a

2

0.1.0 M Fe

solution, which decreases in concentration as the cell operates, and

the cathode compartment contains a2

1.0 M Fe solution which increases in concentration as the cell operates.

D) The anode compartment contains a21.0 M Fe

solution, which decreases in concentration as the cell operates and

the cathode compartment contains a2

0.10 M Fe solution which increases in concentration as the cell operates.

28. Which of the following statements about the lead storage battery is incorrect ?

A) The anode consists of lead and the cathode of lead dioxide.

B) The electrolyte is an aqueous solution of sulphuric acid.

C) As the battery runs down, the density of the electrolyte decreases.

D) As the battery runs down, lead sulphate is formed on the anode and lead sulphite is formed on the cathode.

29. Chromium plating is applied by electrolysis to objects suspended in a dichromate solution, according to the following

(unbalanced) half reaction :2

2 27 ( ) ( ) ( ) ( )Cr O aq e H aq Cr s H O I

How many hours would it take to apply a chromium plating of thickness2

2.0 10 mm to a car bumper of surface area

20.25m in an electrolysis cell carrying a current of 75.0 A ? [ The density of chromium is

37.19 / g cm .]

A) 2.2 h B) 1.5 h C) 3.0 h D) 0.25 h

30. Calculate the concentration of ,Cu at 10°C, when the cell potential for the following reaction is 0.06V and

2[ ] 1.2Cu M and2[ ] 3.5 .[ ( / ) 0.15Cl M E Cu Cu V and

2( / ) 1.36 ; E Cl Cl V 2 2( / , 0.27 )] E Hg Cl Hg Cl V



22 2( ) 2 ( ) 2 ( ) 2 ( ) 2 ( ) Hg Cl s Cu aq Cu aq Hg I Cl aq

A) 0.30M B) 0.41M C) 0.46M D) 1.0M

31. Consider the following diagram:

V

Pt(s) Ni(s)

Salt bridge

1.00 ( ) M Ni aq 21.00 ( )

1.00 ( )

M Cl aq

M Cl aq

Which of the following describes what happens to the concentrations of2 Ni

, 2Cl and Cl , and the masses of the Ni

and Pt electrodes as this galvanic cell generates an electrical current spontaneously at 25°C?

2[ ] Ni 2[ ]Cl [ ]Cl Mass(Ni) electrode Mass(Pt) electrode

A) decreases increases decreases decreases no change

B) decreases increases increases increases decreases

C) increases decreases increases decreases increases

D) increases decreases increases decreases no change

32. Calculate the free energy change per mole of2Cu

formed in the following reaction at 25°C.

22 2Cu Ag Ag Cu

22 ; 0.34 ;Cu e Cu E V

2 2 ; 2.37 ; Mg e Mg E V

A) 0.46 kJ B) 89 kJ C) 44.5 kJ D) -89 kJ

33. What would you observe if you set up the following electrochemical cell :

3 3| (0.001 ) | (1 ) | ? Ag AgNO M AgNO M Ag

A) Electrons will flow from left to right, causing a decrease in the 3 AgNO concentration in the left cell, and an increase in

the 3 AgNO concentration in the right cell.



B) Electrons will flow from right to left, causing an increase in the 3 AgNO concentration in the left cell, and a decrease in


C) Electrons will flow from left to right, causing an increase in the 3 AgNO concentration in the left cell, and a decrease in

3 AgNO concentration in the right cell.

D) Electrons will flow from right to left, causing a decrease in the 3 AgNO concentration in the left cell, and an increase in


34. What is E° for the half reaction given the following ?

2 ( ) 2 ( ) 2 ; ? MX s e M s X E

22 ( ); 0.100 M e M s E V

2 10

2 ( ) 2 ; sp MX s M X K e

A)0.0592 1

0.1002 sp

E In K

B)0.0592 1

0.1002 sp

E Iog K

C)0.0592

0.1002

sp E Iog K D)0.0592 1

0.1002 sp

E Iog K

35. Which of the following offers the best explanation for the fact that E° values are independent of the amount of reaction?

A) As the free – energy change increases, the number of electrons transferred decreases.

B) The free – energy change of a reaction is independent of the amount of reaction.

C) The number of electrons transferred in a reaction is independent of the amount of reaction.

D) As the free – energy change increases, the number of electrons transferred also increases.

36. Which of the following is not true regarding the relationship of the free – energy change and the cell potential of a galvanic

cell?

A) The free – energy change and the cell potential of a galvanic cell are quantitative measures of the driving force of a

chemical reaction.

B) Both the free – energy change and the cell potential are dependent on the composition of the reaction mixture.

C) The free – energy change is directly proportional to the cell potential.

D) If the free – energy change indicates spontaneous reaction, then the cell potential has a negative value.

37. ( ) ( ); 0.800 Ag aq e Ag s E V



( ) ( ) ( ); 0.071 AgBr s e Ag s Br aq E V

2( ) 2 ( ); 1.066 Br I e Br aq E V

Use some of the data above to calculate sp K at 25 C for . AgBr

A) 26.3 10 B) 134.9 10 C) 151.9 10 D) 342.4 10

38. How long must a 50.0A current be passed through an electrolytic cell for refining copper to produce 3.00 mol of copper?

A) 1.50 hrs B) 1.61 hrs C) 2.50 hrs D) 3.00 hrs

39. Calculate the cell potential E at 25 C for the reaction2 32 ( ) 3 ( ) 2 ( ) 3 ( ) Al s Fe aq Al aq Fe s

Given that2 3[ ] 0.020 ,[ ] 0.10 , Fe M Al M and the standard reduction potential is -1.66 V for

3 / Al Al

and -0.45 V for2 / . Fe Fe

A) +1.03V B) +1.17V C) +1.18V D) +1.20V

40. The cell reaction for a lead storage battery is:

2 4 4 2( ) ( ) 2 ( ) 2 ( ) ( ) 2 ( ); 1.92 Pb s PbO s H aq HSO aq PbSO s H O I E V

To provide a potential of about 12V, one could

A) adjust the pH to 12

B) adjust the pH to 1

C) connect six cells in series

D) greatly increase the surface area of the Pb(s) and 2 ( ) PbO s

41. Which of the following statements concerning the rusting of iron is false?

A) The oxidation site can occur at a different place on the metal surface than the reduction site.

B) The metal is reduced.

C) The rusting of iron requires both oxygen and water.

D) Salt increases the rate of corrosion by providing ions to carry the current.

42. Consider the effect of each of the following changes on the cell voltage for a voltaic cell using following reaction:

22( ) 2 ( ) ( ) ( ) Zn s H aq Zn aq H g

(i) The pressure of the 2 H gas is decreased.

(ii) The area of the anode is doubled.



(iii) H concentration is increased by the addition of 2 4 H SO to the anode compartment.

(iv) Sodium nitrate is added to the anode compartment.

In which case(s) does the cell voltage increase?

A) (i) B) (iv) C) (ii) D) (i) and (iii)

43. Given the following standard reduction potentials

2

3 2 2

( ) 2 2 ; 1.36

16 5 3 ; 1.20

2

Cl g e Cl E V

IO H e I H O E V

What would happen if you made a galvanic cell containing 31 M KIO , 1 M H , and 21 M I on one side and the other

side had 1atm 2Cl and 1 M HCl ? (Assume appropriate electrodes and salt bridge).

A) The cell would not work because the oxidizing agents should be all in the same side.

B) 2 I would turn into 3 IO and 2Cl would turn into Cl

C) 2 I would react with 3 IOand 2Cl would react with Cl

D) 3 IO

would turn into 2 I and 2Cl would turn into Cl

44. Given the following standard reduction potentials (25°C)

2

2

( ) 2 ; 0.310

; 0.800

; 0.520

( ) 2 ; 0.440

Ag CN e Ag CN E V

Ag e Ag E V

Cu e Cu E V

Cu CN e Cu CN E V

Calculate ( )orxnG inkJ for the following reaction at 25°C:

2 2( ) ( )Cu CN Ag Ag CN Cu

A) -14.5 B) 12.5 C) 14.5 D) -12.5

45. Given the reaction, 2 2 22 ( ) ( ) ( ) Hg I Cl g Hg Cl s . Assume that the standard0cell

E voltage is related to the

Celsius temperature by the following equation and all substances are at standard state. In doing this, you can assume any

temperature(s) you desire.

At0298 (25 ), K C

0 1.058cell

E volts.



0 01.058 0.00017 ( 25 )

cell E t C

The0 H (in kJ) for the reaction (as written) at 298 K is

A) -321 B) +107 C) -194.4 D) -214

46. What is the voltage of a galvanic cell that does 788J of work when 255C of charge is transferred ?

A)52.01 10 V B) 0.324V C) 3.09V D) 0.324 V

47. Calculate sp K for 2( ) PbI s at0

25 C

2 ( ) 2 ( ) 2 ( ); PbI s e Pb s I aq 0 0.365 E V

2( ) 2 ( ); Pb aq e Pb s 0 0.126 E V

A)13

4.5 10 B)5

9.1 10 C)17

2.5 10 D)9

8.3 10

48. Consider the two reactions below and circle the false

Statement .

1.2

( ) 2 ( ) ( ) 2 ( )Cu s Ag aq Cu aq Ag s

0 01 1

,cell

G E

2.2

2 ( ) 4 ( ) 2 ( ) 4 ( )Cu s Ag aq Cu aq Ag s

0 02 2

,cell

G E

A)0

E for both reaction is0 /G nF B)

0 02 1

2G G

C) n (no.of e transferred) in reaction 2=2n in reaction 1

D)0 0

(2) (1)2

cell cell E E

49. Given the following reduction potentials. What is the product at the anode when a current is passed through an aqueous

solution of 2 FeBr ? (Hint : Remember, which chemicals and ions are really in the solution and subject to the electrolysis)

2 2 2 Br e Br ;

0 1.08 E V



2 24O H H O ;.0

0.82 E V

2 2 Fe e Fe ;0 0.44 E V

2 22 2 ( ) 2 H O e H g OH ;0

0.83 E V

A) Fe B) 2 Br C) 2O D) 2 H

50. For the voltaic cell based on this reaction :

22 ( ) ( ) 2 Ag aq Cu Cu aq Ag

The concentrations of the aqueous ions and sizes of the electrodes can be changed independently. Which statement is

correct ?

A) Increasing the2

[ ]Cu two-fold has the same effect on the cell voltage as increasing the [ ] Ag four-fold.

B) Decreasing the2

[ ]Cu ten-fold has the same effect on the cell voltage as decreasing the [ ] Ag by the same ratio

C) Decreasing the2[ ]Cu

ten-fold has less effect on the cell voltage than decreasing the [ ] Ag by the same amount

D) Doubling the sizes of the cathode has exactly the same effect on the cell voltage as decreasing the2[ ]Cu

by a factor

of two.

51. Which of the following graph correctly illustrates the dependence of the cell voltage, cell E , on the pH for the reaction,

22 ( ) ( ) 2 ( ) 2 ( ) Ag aq H g Ag s H aq

Assume the silver ion remains constant at, [ ] Ag = 1.0M and the 2 H pressure remains constant at 1atm

A) pH

cell E

B) pH

cell E

C) pH

cell E

D) pH

cell E

52. With the knowledge sp K for 2( ) Mg OH 11( 1.8 10 ) sp K , a chemist constructed the cell shown bellow. The left

half contains a buffer solution (pH = ?) saturated with 2( ) Mg OH while the right half-cell contains2

Cu

at 0.1M. The

measured cell voltage was 2.7V. 22 , ? 1 Mg Mg OH S buffer pH Cu M Cu the pH in the left

half-cell is (closest). 22

2.7 , / 0.3 E Mg OH V Cu Cu V



A) 5 B) 9 C) 6 D) 10

53. which of the following statements concerning conductance and molar conductance is true?

A) Both conductance and molar conductance increase on increasing concentration

B) Both conductance and molar conductance decrease on increasing concentration

C) Conductance increases but molar conductance decrease on increasing concentration

D) Conductance decreases but molar conductance increases on increasing concentration

54. Which of the following statements concerning concentration dependence of molar conductivity for a strong and a weak

electrolytes.

A) Molar conductivity decreases linearly on increasing concentration for both types of electrolytes.

B) Molar conductivity decreases linearly on increasing concentration for both types of electrolytes

C) Molar conductivity increases linearly on dilution for strong electrolytes but it is constant for weak electrolyte

D) On dilution, molar conductivity increases linearly for strong electrolyte but for weak electrolyte, the increase is gradual in

higher concentration range but very rapid in lower concentration range.

55. Given the following molar conductivity at infinite dilution and 25 C,

2 1: 426.2m HCl S cm mol

2 1: 271.5m KOH Scm mol

2 13 : 114.42mCH COOK S cm mol The molar conductance at infinite dilution and 25 C f or acetic acid

solution is

A)2 1

583.28S cm mol B)2 1

269.12S cm mol C)2 1

289.63S cm mol D)2 1

172.94S cm mol

56. Consider the following standard reduction potentials.

22 ; 0.34Cu aq e Cu s E V

4 2 22 3 4 ; 0.59 MnO aq H O l e MnO s OH aq E V

2 3 2 2 22 2 2 ; 0.68O g H O aq e H O aq H O l E V

and the following redox reactions:

(i) 22 2 2 2 22 2 H O aq H O l Cu aq O g H O aq Cu s

(ii)2

4 2 22 ( ) 4 ( ) 3 ( ) 3 ( ) 2 ( ) 8 ( ) MnO aq H O I Cu s Cu aq MnO s OH aq



(iii) 4 2 2 2 2 3 22 ( ) 10 ( ) 3 ( ) 3 ( ) 6 ( ) 2 ( ) 8 ( ) MnO aq H O I H O aq O g H O aq MnO s OH aq

Which of the redox reactions above will be sponataneous under standard conditions?

A) (i) only B) (ii) only C) (i) and (iii) D) (ii) and (iii)

57. Use the Standard Reduction potentials given below to calculate f K for2

3 4( ) Zn NH at 25 C .

2 23 3 4

( ) 4 ( ) ( ) ( ), ? f Zn aq NH aq Zn NH aq K

23 34

( ) 2 ( ) 4 ( ); 1.04 Zn NH e Zn s NH aq E V

2 ( ) 2 2 ( ); 0.76 Zn aq e e Zn s E V

A)186 10 B)

93 10 C)62 10 D)

93 10

58. Which one of the following statements is (are) true regarding galvanic and electrolytic cells?

A) In both cells, redox reactions take place.

B) In electrolytic cells, a current is forced through a cell to produce a chemical change for which the cell potential is negative.

C) In both cells, reduction takes place at the cathode.

D) The ion flow through the salt bridge in galvanic cell is opposite to the flow in electrolytic cell.

59. Consider the sequence 1 2o o E E a b c

E A A A

Given that

1 2

2

o o E E E

, which of the following might

represent correct set of values for a,b and c?

A) 3, 2, 1a b c B) 5, 3, 1a b c

C) 6, 4, 4a b c D) 6, 4, 3a b c

60. The specific conductivity of a saturated solution of AgCl is4 1

3.4 10 S cm at 25 C . If

2 1 2 1( ) 62.3 , ( ) 67.7 , Ag S cm mol Cl S cm mol

solubility of AgCl at 25 C is.

A)52.6 10 M B)

33.73 10 / g L C)53.7 10 M D)

32.6 10 / g L

61. In a standard solution of X and Y ions, gas 2 Z is passed. 2 X is liberated and Z is formed while Y remain

unaffected. ,o o x y E E and

o z E represent standard reduction potentials of 2 2 2, X Y and Z respectively. Which of the

following can be inferred from this equation?



A)o o

z x E E B)o o

z y E E C)o o y x E E D)

1( )

2

o o o z x y E E E

62. The standard emf of the following Cell: 2( ) | ( )(0.10 ) || ( ) | ( )Cd s CdCl aq M AgCl s Ag s In which the cell reaction

is22 ( ) ( ) 2 ( ) ( ) 2 ( ) AgCl s Cd s Ag s Cd aq Cl aq is 0.6915 V at 0°C and 0.6753 V at 25°C. The H

of reaction at 25°C is

A) -176 kJ B) -234 kJ C) 123.5 kJ D) -167.26 kJ

Passage:

An electrochemical cell with inert platinum electrodes is shown below. The half cell reactions are:

3 2; 0.77 Fe e Fe E V

2 322 ; 0.34VO H e V H O E V

Voltmeter

KCl

Pt Pt

3 2,V VO and H 3 2, Fe Fe and cl

63. The statement which is incorrect about this cell is

A) cell E is 0.43 V.

B) Electrons flow from left to right electrode.

C) If some3 Fe

is added to left half-cell, cell E increases.

D) If some 3VCl is added to right half-cell, cell E increases.

64. Emf of the cell when all the species are at 1.0M except H which is at 0.01M is

A) 1.35 V B) 0.55 V C) 0.67 V D) 0.194 V

65. The maximum useful work that can be obtained from this cell under standard condition is

A) 32.8 kJ B) 41.5 kJ C) 74.3 kJ D) 107 kJ

Passage:



For the next three questions, consider these half reactions and corresponding E° values at 25°C.

(A)2

2 2( ) 4 ( ) 2 2 ( ); 1.23 MnO s H aq e H O Mn aq E V

(B)2

( ) 2 ( ); 0.34Cu aq e Cu s E V

(C) ( ) ( ); 0.80 Ag aq e Ag s E V

(D)2

( ) 2 ( ); 0.13 Pb aq e Pb s E V

(E)2

( ) 2 ( ); 2.34 Mg aq e Mg s E V

66. Which half-reaction(s) would oxidize 2( ) H g to ( )? H aq

A) A-only B) B and E only C) D and E only D) A,B and C

67. If a current is passed through an aqueous solution containing 3 2 3( ) ,Cu NO AgNO and 3 2( ) Mg NO , the order in

which metals are deposited at cathode is (first metal is one that is deposited first):

A) Ag, Cu, Mg B) Mg, Cu, Ag C) Cu, Ag D) Ag, Cu

68. Note these additional half-reactions and E° values:

2( ) 2 2 ( ); 1.36Cl g e Cl aq E V

2( ) 2 2 ( ); 0.54 I g e l aq E V

Which of the lettered half-reactions will oxidize I but not Cl

?

A) B only B) A and C only C) D and E only D) B and D only

69. Equivalent conductance of 0.2M aqueous solution of a weak monobasic acid (HA) is210S cm

1equiv and that at

infinite dilution is2

200 S cm 1equiv

. Hence, pH of this solution is

70. A 250 mL of aqueous NaCl solution is electrolysed for 1.0 min using a current of 8 ma at 25°C. What is the pH of the final

solution? ( 96000 ) F C

71. Emf of a cell corresponding to the reaction :2

2( ) 2 ( ) ( )[0.10 ] ( )[1.0 ] Zn s H aq Zn aq M H g atm is

0.3175V at 25°C. Also, at 25°C2 /

0.76 .o

Zn Zn E V

The pH of solution in cathode chamber is

72. 2.0 L of a buffer solution is prepared, that is 1.0 M 2 4 NaH PO and 2 41.0 M Na HPO . The solution is divided into two

halves between two compartments of an electrolyte cell using Pt-electrodes. Assume that the only reaction is the electrolysis

of water. If electrolysis is carried out for 212 min with a current of 1.25A; pH of the anode compartment is approximately.



73. A current of 0.01 A is passed through a solution of iridium bromide. Theonly reaction at the cathode is the deposition of

iridium metal. After 3.0 hrs, 0.072 g of Ir is deposited. The oxidation state of iridium ion ( atomic weight = 192 ) is

74. If an aqueous NaCl solution is electrolysed using a current of 5 A for 200 Min, Volume of 2 ( )Cl g in litres, produced under

STP condition is (F=96000C).

KEY:

1)B 2)A 3)C 4)D 5)D 6)D 7)D 8)D 9)B 10)C 11)A 12)D 13)A

14)B 15)D 16)C 17)A 18)D 19)C 20)B 21)A 22)E 23)C 24)B 25)D

26)C 27)B 28)D 29)B 30)B 31)D 32)D 33)A 34)B 35)C 36)B

37)B 38)D 39)C 40)C 41)B 42)D 43)B 44)A 45)D 46)C 47)D

48)D 49)C 50)C 51)B 52)B 53)C 54)D 55)B 56)B 57)B 58)A,B,C

59)A,B,C 60)A,B 61)A,C 62)D 63)D 64)C 65)B 66)D 67)D 68)B

69)2 70)9 71)8 72)2 73)3 74)7

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