Quiz about ELECTROCHEMISRY IN GENERAL AWARENESS

Question 1

Consider the cell `H_(2)(Pt)`|(H_(3)O^(+)(aq))(pH= 5.03)||(Ag^(+))(xM)|Ag`. The measured EMF of the cell is 1.0V. What is the value of x? `[E_(Ag^(+)Ag)^(@) = +0.8V][T = 25^(@)C]`A. `2xx10^(-2)M`B. `2xx10^(-3)M`C. `1.5xx10^(-3)M`D. `1.5xx10^(-2)M`

Accepted Answer

NA

Question 2

`Pt|underset((p_(1)))(H_(2))|underset((1M))(H^(+))||underset((1M))(H^(+))|underset((p_(2)))(H_(2))|Pt` (where `p_(1)` and `p_(2)` are pressure) cell reaction cell reaction will be spontaneous ifA. `p_(1)=p_(2)`B. `p_(1)gtp_(2)`C. `p_(2)gtp_(1)`D. `p_(1)=1atm`

Accepted Answer

NA

Question 3

What will be the emf for the given cell ? `Pt|H_(2)(gP_(1))|H^(+)(aq)|H_(2)(gP_(2))|Pt`A. `(RT)(F)log_(e)(p_(1))(p_(2))`B. `(RT)(2F)log_(e)(p_(1))(p_(2))`C. `(RT)(F)log_(e)(p_(2))(p_(1))`D. `(RT)(2F)log_(e)^(p_(2))(p_(1))`

Accepted Answer

NA

Question 4

A galvanic cell is compsed of two hydrogen electrodes one of which is a standard one. In which of the following solutions should the other electrode be immersed to get maximum emf? `K_(a)(CH_(3)COOH) = 2 xx 10^(-5)` `K_(a)(H_(3)PO_(4)) = 10^(-3)`.A. 0.1 M HClB. 0.1 M `CH_(3)COOH`C. `0.1M` `H_(2)PO_(4)`D. `0.1 M H_(2)SO_(4)`

Accepted Answer

NA

Question 5

Equinormal solutions of two weak acids `HA(pK_(a)=3)` and `HB(pK_(a)=5)` are each placed in contact with standard hydrogen electrode at `25^(@)C(T=298K)` when a cell is constructed by interconnecting them through a salt bridge find the e.m.f. of the cell.

Accepted Answer

NA

Question 6

Cadmium amalgam is prepared by electrolysis of a solution of `CdCl_(2)` using a mercury cathode. Find how long a current of 5 ampere should be passed in order to prepare 12% Cd-Hg amalgam on a cathode of 2 g mercury. At mass of Cd=112.40.

Accepted Answer

NA

Question 7

The number of electrons delivered at the cathode during electrolysis by a current of `1` ampere in 60 seconds is (charger on electron `= 1.60 xx 10^(-19)C`)A. `3.74xx10^(20)`B. `6.0xx10^(23)`C. `7.48xx10^(21)`D. `6.0xx10^(20)`

Accepted Answer

NA

Question 8

Which of the following statement is true for the electrochemical Daniell cell ?A. electrons flows from copper electrode to zinc electrode.B. Current flows from zinc electrode to copper electrode.C. Cations moves towards copper electrodes.D. cations moves towards zinc electrode.

Accepted Answer

NA

Question 9

the standard reduction potenital of a silver chloride electrode is 0.2 V and that of a silver electrode is 0.79 V. The maximum amount of AgCl that can dissolve in `10^(6)`L of a 0.1 M `AgNO_(3)` solution isA. 0.5 mmolB. 1.0 mmolC. 2.0 mmolD. 2.5 mmol

Accepted Answer

NA

Question 10

A cell `Cu|Cu^(++)||Ag^(+)|Ag` initially contains `2MAg^(+)` and `2MCu^(++)` ions in 1 L electrolyte. The change in cell potential after the passage of 10 amp. Curret for 4825 sec isA. `-0.00738V`B. `-1.00738V`C. `-0.0038V`D. none

Accepted Answer

NA

Question 11

The equivalent conductivity of `KCl` at infinite dilution is `130S cm^(2) eq^(-1)`. The transport number of `Cl^(-)` ion in `KCl` at the same temperature is `0.505`. The limiting ionic mobility of `K^(+)` ion is A. `6xx67xx10^(-4)cm^(2)sec^(-1)volt^(-1)`B. `5.01xx10^(-3)cm^(2)sec^(-1)volt^(-1)`C. `3.22xx10^(-4)cm^(2)sec^(-1)volt^(-1)`D. `2.00xx10^(-4)cm^(2)sec^(-1)volt^(-1)`

Accepted Answer

NA

Question 12

Strong acid versus strong base The principle of conductometric titrations is based on the fact that during the titration one of the ions is replaced by the other and invariable these two ions differ in the ionic conductivity with the result that thhe conductivity of the solution varies during the course of the titration. take for example the titration between a strong acid say HCl and a string base say NaOH before NaOH is added the conductance of HCl solution has a high value due to the presence of highly mobile hydrogen ions. As NaOH is added `H^(+)` ions are replaced by relatively slower moving `Na^(+)` ions. consequently the conductance of the solution decreases and this continues right upto the equivalence point where the solution contains only NaCl. Beyond the equivalence point if more of NaOH is added then the solution contains a excess of the fast moving `OH^(-)` ions with the result that its conductance is increased ad it condinues to increase as more and more of NaOH is added. If we plot the conductance value versus the amount of NaOH added we get a curve of the type shown in Fig. The descending portion AB represents the conductances before the equivalence point (solution contains a mixture of acid HCl and the salt NaCl) and the ascending portion CD represents the conductances after the equivalence point (solution contains the salt NaCl and the excess of NaOH). The point E which represent the minium conductance is due to the solution containing only NaCl with no free acid or alkali and thus represents the equivalence point. this point can however be obtained by the extrapolation of the lines AB and DC and therefore one is not very particular in locating this point expermentally as it is in the case of ordinary acid-base titrations involving the acid-base indicators. Weak acid versus strong base Let us take specific example of acetic acid being titrated against `NaOH`. Before the addition of alkali the solution shows poor conductance due to feeble ionization of acetic acid. Initially the addition of alkali causes not only the replacement of `H^(+)` by `Na^(+)` but also suppresses the dissociation of acetic acid due to the common ion `Ac^(-)` and thus the conductance of the solution decreases in the beginning. but very soon the conductance start increasing as addition of NaOH neutralizes the undissociated HAc to `Na^(+)Ac^(-)` thus causing the replacement of non-conducting HAc with Strong-conducting electrolyte `Na^(+)Ac^(-)`. the increase in conductance continuous right up to the equivalence point. Beyond this point conductance increases more rapidly with the addition of NaOH due to the highly conducting `OH^(-)` ions the graph near the equivalence point is curved due to the hydrolysis of the salt `NaAc`. The actual equivalence point can as usual be obtained by the extrapolation method. In all these graphs it has been assumed that the volume change due addition of solution from burrette is negnigible hence volume change of the solution in beaker the conductance of which is measured is almost constant throughout the measurement. Q. The most appropriate titration curve obtained when a mixture of a strong acid (say HCl) and a weak acid (say `CH_(3)COOH`) is titrated with a strong base (say NaOH) will beA. B. C. D.

Accepted Answer

NA

Question 13

Strong acid versus strong base The principle of conductometric titrations is based on the fact that during the titration one of the ions is replaced by the other and invariable these two ions differ in the ionic conductivity with the result that thhe conductivity of the solution varies during the course of the titration. take for example the titration between a strong acid say HCl and a string base say NaOH before NaOH is added the conductance of HCl solution has a high value due to the presence of highly mobile hydrogen ions. As NaOH is added `H^(+)` ions are replaced by relatively slower moving `Na^(+)` ions. consequently the conductance of the solution decreases and this continues right upto the equivalence point where the solution contains only NaCl. Beyond the equivalence point if more of NaOH is added then the solution contains a excess of the fast moving `OH^(-)` ions with the result that its conductance is increased ad it condinues to increase as more and more of NaOH is added. If we plot the conductance value versus the amount of NaOH added we get a curve of the type shown in Fig. The descending portion AB represents the conductances before the equivalence point (solution contains a mixture of acid HCl and the salt NaCl) and the ascending portion CD represents the conductances after the equivalence point (solution contains the salt NaCl and the excess of NaOH). The point E which represent the minium conductance is due to the solution containing only NaCl with no free acid or alkali and thus represents the equivalence point. this point can however be obtained by the extrapolation of the lines AB and DC and therefore one is not very particular in locating this point expermentally as it is in the case of ordinary acid-base titrations involving the acid-base indicators. Weak acid versus strong base Let us take specific example of acetic acid being titrated against `NaOH`. Before the addition of alkali the solution shows poor conductance due to feeble ionization of acetic acid. Initially the addition of alkali causes not only the replacement of `H^(+)` by `Na^(+)` but also suppresses the dissociation of acetic acid due to the common ion `Ac^(-)` and thus the conductance of the solution decreases in the beginning. but very soon the conductance start increasing as addition of NaOH neutralizes the undissociated HAc to `Na^(+)Ac^(-)` thus causing the replacement of non-conducting HAc with Strong-conducting electrolyte `Na^(+)Ac^(-)`. the increase in conductance continuous right up to the equivalence point. Beyond this point conductance increases more rapidly with the addition of NaOH due to the highly conducting `OH^(-)` ions the graph near the equivalence point is curved due to the hydrolysis of the salt `NaAc`. The actual equivalence point can as usual be obtained by the extrapolation method. In all these graphs it has been assumed that the volume change due addition of solution from burrette is negnigible hence volume change of the solution in beaker the conductance of which is measured is almost constant throughout the measurement. Q. If a 100 mL solution of 0.1 M HBr is titrated using a very concentrated solution of `NaOH` then the conductivity (specific conductance) of this solution at the equivalence point will be (assume volume change is negligible due to addition of NaoH) report your answer after multipling it with 10 in `Sm^(-1)` [Given `lamda_((Na^(+)))^(@)=8xx10^(-3)Sm^(2)mol^(-1)lamda_((Br^(-)))^(@)=4xx10^(-3)Sm^(2)mol^(-1)]`A. `6`B. `12`C. `15`D. `24`

Accepted Answer

NA

Question 14

Acetic acid is titrated with NaOH solution. Which of the following statement is correct for this titration?A. Conductance increases upto equivalence point then it decreasesB. Conductance increases upto equivalence point then it increasesC. first conductance increases slowly upto equivalence point and then increases rapidlyD. first conductance increases slowly upto equivalence point ad then drops rapidly.

Accepted Answer

NA

Question 15

Which statement is correct?A. A solution of copper (II) sulphate can be stored in iron vessel.B. An oxide layer on zinc vessel can be easily removed by washing with dilute `HCl`.C. Molten `PbBr_(2)` is good conductor of electricity because it contains free ions.D. in the reaction `Li+(1)(2)H_(2)toLiH` hydrogen is a reducing agent.

Accepted Answer

NA

Question 16

During the electrolysis of 0.1 M `CuSO_(4)` solution using coppepr electrodes a depletion of `[Cu^(2+)]` occurs near the cathode with a corresponding excess near the anode owing to inefficient stirring of the solution. If the local concentration of `[Cu^(2+)]` near the anode and cathode are respectively 0.12 M and 0.08 M calcualte the back emf developed. Temperature = 298 K.A. 22 mVB. 5.2 mVC. 29 mVD. 59 mV

Accepted Answer

NA

Question 17

The molar conductance of NaCl varies with the concentration as shown in the following table and all values follows the equation. `lambda_(m)^(c)=lambda_(m)^(oo)-bsqrt(C)` where `lambda_(m)^(c)`= molar specific conductance `lambda_(m)^(oo)=` molar specific conductance at infinite dilution C=molar concentration  When a certain conductivity cell (C) was filled with 25`xx10^(-4)(M) NaCl` solution the resistance of the cell was found to be 1000 ohm. At infinite dilution conductance of `Cl^(-)` and `SO_(4)^(2-)` are `80ohm^(-1) cm^(2) mole^(-1)` and `160ohm^(-1) cm^(2) mole^(-1)` respectively. What is the molar conductance of NaCl at infinite dilution?A. `147ohm^(-1)cm^(2)mole^(-1)`B. `107ohm^(-1)cm^(2)smole^(-1)`C. `127ohm^(-1)cm^(2)mole^(-1)`D. `157ohm^(-1)cm^(2)mole^(-1)`

Accepted Answer

NA

Question 18

Statement-1 Copper is dissolved at anode and deposited at cathode when Cu electrodes are used and electrolyte is 1M `CuSO_(4)(aq)` solution. Statement-2 SOP of Cu is less than SOP of water and SRP of Cu is greater than SRP of water.

Accepted Answer

NA

Question 19

The molar conductance of NaCl varies with the concentration as shown in the following table and all values follows the equation. `lambda_(m)^(c)=lambda_(m)^(oo)-bsqrt(C)` where `lambda_(m)^(c)`= molar specific conductance `lambda_(m)^(oo)=` molar specific conductance at infinite dilution C=molar concentration  When a certain conductivity cell (C) was filled with 25`xx10^(-4)(M) NaCl` solution the resistance of the cell was found to be 1000 ohm. At infinite dilution conductance of `Cl^(-)` and `SO_(4)^(2-)` are `80ohm^(-1) cm^(2) mole^(-1)` and `160ohm^(-1) cm^(2) mole^(-1)` respectively. What is the cell constant of the conductivity cell (C)?A. `0.385cm^(-1)`B. `3.86cm^(-1)`C. `38.5cm^(-1)`D. `0.1925cm^(-1)`

Accepted Answer

NA

Question 20

`2Ce^(4+) + Co rightarrow 2Ce^(3+) + Co^(2+) E_(cell)^(@) = 1.89V` `E_(Co^(2+)Co)^(@) = -0.277V`. Hence `E_(Ce^(4+)Ce^(3+))^(@)` isA. 0.805 VB. 1.62 VC. `-0.805 V`D. `-1.61 V`

Accepted Answer

NA

Question 21

Given `E^(@) (Cu^(2+Cu)` = 0.337V` and `E^(@) (Sn^(2+Sn) = -0.136V`. Which of the following statements is correct?A. `Cu^(2+)` ions can be reduced by `H_(2)(g)`B. `Cu` can be oxidized by `H^(+)`C. `Sn^(2+)` ions can be reduced by `H_(2)(g)`D. `Cu` can reduce `Sn^(2+)`

Accepted Answer

NA

Question 22

`Zn+Cu^(2+)(aq)hArrCu+Zn^(2+)(aq).` Reaction quotient is `Q=([Zn^(2+)])([Cu^(2+)])` . Variation of `E_(cell)` with log `Q` is of the type with `OA=1.10` `V.E_(cell) ` will be `1.1591V` when A. `[Cu^(2+)][Zn^(2+)]=0.01`B. `[Zn^(2+)][Cu^(2+)]=0.01`C. `[Zn^(2+)][Cu^(2+)]=0.1`D. `[Zn^(2+)][Cu^(2+)]=1`

Accepted Answer

NA

Question 23

For ` Zn^(2+) Zn E^@ =- 0. 76 V` for `Ag^+ Af E^@ =0.799 V`. The correct statement is .A. The reaction Zn getting reduced Ag getting oxidized is spontaneousB. Z undergoes reduction and Ag is oxidizedC. Zn undergoes oxidation `Ag^(+)` gets reducedD. No suitable answer

Accepted Answer

NA

Question 24

The emf of the cell `Zn|Zn^(2+)(0.01M)|| Fe^(2+)(0.001M) | Fe` at 298 K is 0.2905 then the value of equilibrium constant for the cell reaction isA. `e^((0.32)(0.0295))`B. `10^((0.32)(0.0295))`C. `10^((0.26)(0.0295))`D. `10^((0.32)(0.059))`

Accepted Answer

NA

Question 25

`K_(d)` for dissociation of `[Ag(NH_(3))_(2)]^(+)` into `Ag^(+)` and `NH_(3)` is `6 xx 10^(-8)`. Calculae `E^(@)` for the following half reaction. `AG(NH_(3))_(2)^(+) +e^(-) rarr Ag +2NH_(3)` Given `Ag^(+) +e^(-) rarr Ag E^(@) = 0.799V`

Accepted Answer

NA

Question 26

Calculate the potential of an indicator electrode versus the standard hydrogen electrode which originally contained `0.1M MnO_(4)^(-)` and `0.8M H^(+)` and which was treated with `Fe^(2+)` necessary to reduce `90%` of the `MnO_(4)` to `Mn^(2+)` `MnO_(4)^(-) +8H^(+) +5e rarr Mn^(2+) +H_(2)O E^(@) = 1.51V`

Accepted Answer

NA

Question 27

Which of the following statements is wrong about galvanic cells?A. Cathode is the positive electrodeB. cathode is the negative electrodeC. electrons flow from cathode to anode in the external circuitD. reduction occurs at cathode

Accepted Answer

NA

Question 28

Which of the following isare function(s) of salt-bridge?A. it completes the electrical circuit with electrons flowing from one electrode to the other through external wires ad a flow of ions betwee the two compartments through salt-bridge.B. it minimises the liquid-liquid junction potentialC. both correctD. none of these

Accepted Answer

NA

Question 29

Salt bridge containsA. calomelB. corrosive sublimateC. `H_(2)O`D. agar-agar paste

Accepted Answer

NA

Question 30

The resistance of two electrolytes X and Y ere found to be 45 and 100 respectively when equal volumes of both the solutions were taken in the same cell in two different experiments. If equal volumes of these solutions are mixed in the same cell what will be the conductance of the mixture?

Accepted Answer

NA

Question 31

The highest electrical conductivity of the following aqueous solutions is ofA. 0.1 M acetic acidB. 0.1 M chloroacetic acidC. 0.1 M fluoroacetic acidD. 0.1 M difluoroacetic acid.

Accepted Answer

NA

Question 32

KCl can be used in salt bridge as electrolyte in which of the following cells?A. `Zn|ZnCl_(2)||AgNO_(3)|Ag`B. `Pb|Pb(NO_(3))_(2)||Cu(NO_(3))_(2)|Cu`C. `Cu|CuSO_(4)||AuCl_(3)|Au`D. `Fe|FeSO_(4)||Pb(NO_(3))_(2)|Pb`

Accepted Answer

NA

Question 33

Name te factors which affect electrical conductivity of electrolytes.

Accepted Answer

NA

Question 34

Why is it impossible to obtain the electrode potential for a single electrode?

Accepted Answer

NA

Question 35

What does the negative value of `E_(cell)^(@)` indicate?

Accepted Answer

NA

Question 36

Calculate the cell emf and `triangle_(r)G^(@)` for the cell reactin at `25^(@)C` `Zn(s)|Zn^(2+)(0.1M)||Cd^(2+)(0.01M)|Cd(s)` (given `E_(Zn^(2+)Zn)^(@)=-0.763VE_(Cd^(2+)Cd)^(@)=-0.403V` `1F=96500Cmol^(-1)R=8.314JK^(-1)mol^(-1)]`

Accepted Answer

NA

Question 37

A resistance of `50Omega` is registered when two electrodes are suspended into a beaker containing a dilute solution of a strong electrolyte such that exactly half of them are submerged into solution as shown in figure. If the solution is diluted by adding pure water (negligible conductivity) so as to just completely submerge the electrodes the new ressitance offered by the solution would be ltbegt A. `50Omega`B. `100Omega`C. `25Omega`D. `200Omega`

Accepted Answer

NA

Question 38

In ` H_2 -O_2` fuel cell `6.72 L` of hydrogen at `NTP` reacts in `15` minutes the averge current produced in ampres is .A. 64.3 ampB. 643.3 ampC. 6.43 ampD. 0.643 amp

Accepted Answer

NA

Question 39

The efficiency of a hypothetical cell is about `84%` which involves the following reactions `A(s) + B^(2+)(aq) rightarrow A^(2+)(aq) _ B(s)` `DeltaH = -285kJ` Then the standard electrode potential of the cell will be (Asume `DeltaS = 0)A. 1.2B. 2.40 VC. 1.10 VD. 1.24 V

Accepted Answer

NA

Question 40

Determine range of `E^(@)` values for this reaction `X_(aq)^(2+)+2e^(-)toX(s)` for given conditions (a). If the metal X dissolve in `HNO_(3)` but not in `HCl` it can displace `Ag^(+)` ion but not `Cu^(2+)` ion. (b). If te metal X is HCl acid producing `H_(2)(g)` but does not displace either `Zn^(2+)` or `Fe^(2+)` Given `E_(Ag^(+)Ag)^(0)=0.8V E_(Fe^(2+)Fe)^(0)=-0.44` `E_(Cu^(2+)Cu)^(0)=0.34V E_(NO_(3)^(-)NO)^(0)=0.96V E_(zn^(2+)Zn)^(0)=-0.76V`

Accepted Answer

NA

Question 41

The standard reduction potential value of the three metallic cations X Y and Z are 0.52 `-3.03` and `-1.18V` respectively. Write the decreasing order of reducing power of the corresponding metals.

Accepted Answer

NA

Question 42

How many gm of silver will be displaced from a solution of `AgNO_(3)` by 4gm of magnesium?A. 18 gmB. 4 gmC. 4 gmD. 2 gm

Accepted Answer

NA

Question 43

The moles of electrons required to deposit 1 gm equivalent aluminium (at wt. =27) from a solution of aluminium chloride will beA. 3B. 1C. 4D. 2

Accepted Answer

NA

Question 44

The concentration of potassium ions inside a biological cell is at least 20 times higher than outside. The resulting potential difference across the cell is important in several processes such as transmission of nerve impulses and maintaining the ion balance. A simplel model for a concentration cell involving a metal `M` is `M(s)|M^(o+)(aq0.05 ` molar`)||M^(o+)(aq1` molar`)|M(s)` For the abov electrolytic cell the magnitude of the cell potential is `|E_(cell)|=70mV.` For the above cellA. `E_(Cell)lt0triangleGge0`B. `E_(cell)gt0triangleGlt0`C. `E_(cell)lt0triangleG^(@)gt0`D. `E_(cell)gt0triangleG^(@)lt0`

Accepted Answer

NA

Question 45

The concentration of potassium ions inside a biological cell is at least 20 times higher than outside. The resulting potential difference across the cell is important in several processes such as transmission of nerve impulses and maintaining the ion balance. A simplel model for a concentration cell involving a metal `M` is `M(s)|M^(o+)(aq0.05 ` molar`)||M^(o+)(aq1` molar`)|M(s)` For the abov electrolytic cell the magnitude of the cell potential is `|E_(cell)|=70mV.` If the `0.05` moolar solution of `M^(o+)` is replaced by a `0.0025` molar `M^(o+)` solution then the magnitude of the cell potential would beA. `35mV`B. `70mV`C. `140mV`D. `700mV`

Accepted Answer

NA

Question 46

A current of `9.65` ampere is passed through the aqueous solution `NaCI` using suitable electrodes for `1000s`. The amount of `NaOH` formed during electrolysis isA. 2.0 gB. 4.0 gC. 6.0 gD. 8.0 g

Accepted Answer

NA

Question 47

(a) How many mole of mercury will be produced by electrolysing 1.0 M Hg `(NO_(3))_(2)` solution with a current of 2.00 A for 3 hours? [Hg`(NO_(3))_(2) = 200.6 g mol^(-1)`]. (b) A voltaic cell is set up at `25^(@)`C with the following half-cells `Al^(3+)` (0.001M) and `Ni^(2+)` (0.50M). Write an equation for the reaction that occurs when the cell generates an electric current and determine the cell potential. (Given `E_(Ni^(2+)Ni)^(2)=- 0.25 VE_(Al^(3+)Al)^(@)= - 1.66V`)

Accepted Answer

NA

Question 48

Which of the following facts is not truegtA. If `E^(@)(M^(n+)M)` is negative `H^(+)` will be reduced to `H_(2)` by the metal MB. If `E^(@)(M^(n+)M)` is positive `Mn^(2+)` will e reduced to M by `H_(2)`C. In a cell `M^(n+)M` electrode is attached to hydrogen-half cell. To produce spontaneous cell reaction metal M will act as negative electrode.D. Compounds of active metals `(ZnNaMg)` are reducible by `H_(2)` whereas those of noble metals `(CuAgAu)` are not reducible.

Accepted Answer

NA

Question 49

Adding powdered Pb and Fe to a solution containing 1.0 M each of `Pb^(2+)` and `Fe^(2+)` ions would result into the formation ofA. More of Pb and `Fe^(2+)` ionsB. More of Fe and `Pb^(2+)` ionsC. More of Fe and PbD. More of `Fe^(2+)` and `Pb^(2+)` ions

Accepted Answer

NA

Question 50

Which of the following curve represents the variation of `lambda_(M)` with `sqrt(C)` for `AgNO_(3)`?A. B. C. D.

Accepted Answer

NA

Explore topic-wise InterviewSolutions in Current Affairs.

Consider the cell `H_(2)(Pt)`|{:(H_(3)O^(+)(aq)),(pH= 5.03):}||{:(Ag^(+),),("xM"):}|Ag`. The measured EMF of the cell is 1.0V. What is the value of x? `[E_(Ag^(+),Ag)^(@) = +0.8V][T = 25^(@)C]`A. `2xx10^(-2)M`B. `2xx10^(-3)M`C. `1.5xx10^(-3)M`D. `1.5xx10^(-2)M`

`Pt|underset((p_(1)))(H_(2))|underset((1M))(H^(+))||underset((1M))(H^(+))|underset((p_(2)))(H_(2))|Pt` (where `p_(1)` and `p_(2)` are pressure) cell reaction cell reaction will be spontaneous if:A. `p_(1)=p_(2)`B. `p_(1)gtp_(2)`C. `p_(2)gtp_(1)`D. `p_(1)=1atm`

What will be the emf for the given cell ? `Pt|H_(2)(g,P_(1))|H^(+)(aq)|H_(2)(g,P_(2))|Pt`A. `(RT)/(F)log_(e)(p_(1))/(p_(2))`B. `(RT)/(2F)log_(e)(p_(1))/(p_(2))`C. `(RT)/(F)log_(e)(p_(2))/(p_(1))`D. `(RT)/(2F)log_(e)^(p_(2))/(p_(1))`

Equinormal solutions of two weak acids `HA(pK_(a)=3)` and `HB(pK_(a)=5)` are each placed in contact with standard hydrogen electrode at `25^(@)C(T=298K)` when a cell is constructed by interconnecting them through a salt bridge find the e.m.f. of the cell.

Cadmium amalgam is prepared by electrolysis of a solution of `CdCl_(2)` using a mercury cathode. Find how long a current of 5 ampere should be passed in order to prepare 12% Cd-Hg amalgam on a cathode of 2 g mercury. At mass of Cd=112.40.

The number of electrons delivered at the cathode during electrolysis by a current of `1` ampere in 60 seconds is (charger on electron `= 1.60 xx 10^(-19)C`)A. `3.74xx10^(20)`B. `6.0xx10^(23)`C. `7.48xx10^(21)`D. `6.0xx10^(20)`

Which of the following statement is true for the electrochemical Daniell cell ?A. electrons flows from copper electrode to zinc electrode.B. Current flows from zinc electrode to copper electrode.C. Cations moves towards copper electrodes.D. cations moves towards zinc electrode.

the standard reduction potenital of a silver chloride electrode is 0.2 V and that of a silver electrode is 0.79 V. The maximum amount of AgCl that can dissolve in `10^(6)`L of a 0.1 M `AgNO_(3)` solution is:A. 0.5 mmolB. 1.0 mmolC. 2.0 mmolD. 2.5 mmol

A cell `Cu|Cu^(++)||Ag^(+)|Ag` initially contains `2MAg^(+)` and `2MCu^(++)` ions in 1 L electrolyte. The change in cell potential after the passage of 10 amp. Curret for 4825 sec is:A. `-0.00738V`B. `-1.00738V`C. `-0.0038V`D. none

Statement-1: Copper is dissolved at anode and deposited at cathode when Cu electrodes are used and electrolyte is 1M `CuSO_(4)(aq)` solution. Statement-2: SOP of Cu is less than SOP of water and SRP of Cu is greater than SRP of water.

`2Ce^(4+) + Co rightarrow 2Ce^(3+) + Co^(2+), E_(cell)^(@) = 1.89V` `E_(Co^(2+)//Co)^(@) = -0.277V`. Hence `E_(Ce^(4+)//Ce^(3+))^(@)` isA. 0.805 VB. 1.62 VC. `-0.805 V`D. `-1.61 V`

Given : `E^(@) (Cu^(2+//Cu)` = 0.337V` and `E^(@) (Sn^(2+//Sn) = -0.136V`. Which of the following statements is correct?A. `Cu^(2+)` ions can be reduced by `H_(2)(g)`B. `Cu` can be oxidized by `H^(+)`C. `Sn^(2+)` ions can be reduced by `H_(2)(g)`D. `Cu` can reduce `Sn^(2+)`

For ` Zn^(2+) //Zn, E^@ =- 0. 76 V`, for `Ag^+ //Af E^@ =0.799 V`. The correct statement is .A. The reaction Zn getting reduced Ag getting oxidized is spontaneousB. Z undergoes reduction and Ag is oxidizedC. Zn undergoes oxidation `Ag^(+)` gets reducedD. No suitable answer

The emf of the cell, `Zn|Zn^(2+)(0.01M)|| Fe^(2+)(0.001M) | Fe` at 298 K is 0.2905 then the value of equilibrium constant for the cell reaction is:A. `e^((0.32)/(0.0295))`B. `10^((0.32)/(0.0295))`C. `10^((0.26)/(0.0295))`D. `10^((0.32)/(0.059))`

`K_(d)` for dissociation of `[Ag(NH_(3))_(2)]^(+)` into `Ag^(+)` and `NH_(3)` is `6 xx 10^(-8)`. Calculae `E^(@)` for the following half reaction. `AG(NH_(3))_(2)^(+) +e^(-) rarr Ag +2NH_(3)` Given `Ag^(+) +e^(-) rarr Ag, E^(@) = 0.799V`

Which of the following statements is wrong about galvanic cells?A. Cathode is the positive electrodeB. cathode is the negative electrodeC. electrons flow from cathode to anode in the external circuitD. reduction occurs at cathode

Salt bridge containsA. calomelB. corrosive sublimateC. `H_(2)O`D. agar-agar paste

The resistance of two electrolytes X and Y ere found to be 45 and 100 respectively when equal volumes of both the solutions were taken in the same cell in two different experiments. If equal volumes of these solutions are mixed in the same cell, what will be the conductance of the mixture?

The highest electrical conductivity of the following aqueous solutions is ofA. 0.1 M acetic acidB. 0.1 M chloroacetic acidC. 0.1 M fluoroacetic acidD. 0.1 M difluoroacetic acid.

KCl can be used in salt bridge as electrolyte in which of the following cells?A. `Zn|ZnCl_(2)||AgNO_(3)|Ag`B. `Pb|Pb(NO_(3))_(2)||Cu(NO_(3))_(2)|Cu`C. `Cu|CuSO_(4)||AuCl_(3)|Au`D. `Fe|FeSO_(4)||Pb(NO_(3))_(2)|Pb`

Name te factors which affect electrical conductivity of electrolytes.

Why is it impossible to obtain the electrode potential for a single electrode?

What does the negative value of `E_("cell")^(@)` indicate?

Calculate the cell emf and `triangle_(r)G^(@)` for the cell reactin at `25^(@)C` `Zn(s)|Zn^(2+)(0.1M)||Cd^(2+)(0.01M)|Cd(s)` (given `E_(Zn^(2+)//Zn)^(@)=-0.763V,E_(Cd^(2+)//Cd)^(@)=-0.403V` `1F=96500Cmol^(-1),R=8.314JK^(-1)mol^(-1)]`

In ` H_2 -O_2` fuel cell, `6.72 L` of hydrogen at `NTP` reacts in `15` minutes, the averge current produced in ampres is .A. 64.3 ampB. 643.3 ampC. 6.43 ampD. 0.643 amp

The efficiency of a hypothetical cell is about `84%` which involves the following reactions: `A(s) + B^(2+)(aq) rightarrow A^(2+)(aq) _ B(s)` `DeltaH = -285kJ` Then, the standard electrode potential of the cell will be: (Asume `DeltaS = 0)A. 1.2B. 2.40 VC. 1.10 VD. 1.24 V

The standard reduction potential value of the three metallic cations X, Y and Z are 0.52, `-3.03` and `-1.18V` respectively. Write the decreasing order of reducing power of the corresponding metals.

How many gm of silver will be displaced from a solution of `AgNO_(3)` by 4gm of magnesium?A. 18 gmB. 4 gmC. 4 gmD. 2 gm

The "mole"s of electrons required to deposit 1 gm equivalent aluminium (at wt. =27) from a solution of aluminium chloride will be:A. 3B. 1C. 4D. 2

A current of `9.65` ampere is passed through the aqueous solution `NaCI` using suitable electrodes for `1000s`. The amount of `NaOH` formed during electrolysis isA. 2.0 gB. 4.0 gC. 6.0 gD. 8.0 g

Adding powdered Pb and Fe to a solution containing 1.0 M each of `Pb^(2+)` and `Fe^(2+)` ions would result into the formation of:A. More of Pb and `Fe^(2+)` ionsB. More of Fe and `Pb^(2+)` ionsC. More of Fe and PbD. More of `Fe^(2+)` and `Pb^(2+)` ions

Which of the following curve represents the variation of `lambda_(M)` with `sqrt(C)` for `AgNO_(3)`?A. B. C. D.

1.	Consider the cell `H_(2)(Pt)`\|{:(H_(3)O^(+)(aq)),(pH= 5.03):}\|\|{:(Ag^(+),),("xM"):}\|Ag`. The measured EMF of the cell is 1.0V. What is the value of x? `[E_(Ag^(+),Ag)^(@) = +0.8V][T = 25^(@)C]`A. `2xx10^(-2)M`B. `2xx10^(-3)M`C. `1.5xx10^(-3)M`D. `1.5xx10^(-2)M`
Answer» Correct Answer - A

2.	`Pt\|underset((p_(1)))(H_(2))\|underset((1M))(H^(+))\|\|underset((1M))(H^(+))\|underset((p_(2)))(H_(2))\|Pt` (where `p_(1)` and `p_(2)` are pressure) cell reaction cell reaction will be spontaneous if:A. `p_(1)=p_(2)`B. `p_(1)gtp_(2)`C. `p_(2)gtp_(1)`D. `p_(1)=1atm`
Answer» Correct Answer - B

3.	What will be the emf for the given cell ? `Pt\|H_(2)(g,P_(1))\|H^(+)(aq)\|H_(2)(g,P_(2))\|Pt`A. `(RT)/(F)log_(e)(p_(1))/(p_(2))`B. `(RT)/(2F)log_(e)(p_(1))/(p_(2))`C. `(RT)/(F)log_(e)(p_(2))/(p_(1))`D. `(RT)/(2F)log_(e)^(p_(2))/(p_(1))`
Answer» Correct Answer - B The `E^(@)` of cell will be zero.

4.	A galvanic cell is compsed of two hydrogen electrodes, one of which is a standard one. In which of the following solutions should the other electrode be immersed to get maximum emf? `K_(a)(CH_(3)COOH) = 2 xx 10^(-5)` ,`K_(a)(H_(3)PO_(4)) = 10^(-3)`.A. 0.1 M HClB. 0.1 M `CH_(3)COOH`C. `0.1M` `H_(2)PO_(4)`D. `0.1 M H_(2)SO_(4)`
Answer» Correct Answer - B `E_(cell)=0.059log((C_(1))/(C_(2)))` ltbr. For `E_(cell)` to be `+ve` and maximum `(C_(1))/(C_(2))lt1` or `C_(1)ltC_(2)` give `C_(2)=1M`. `thereforeC_(1)` should be the minimum conc. Of `H^(+)` `therefore` (b) is the right answer

5.	Equinormal solutions of two weak acids `HA(pK_(a)=3)` and `HB(pK_(a)=5)` are each placed in contact with standard hydrogen electrode at `25^(@)C(T=298K)` when a cell is constructed by interconnecting them through a salt bridge find the e.m.f. of the cell.
Answer» Correct Answer - `E=0.059V` `Pt//H_(2)^(@)//H^(+)(HA)//H^(+)(HB)//H_(2)//Pt` `H_(2)to2H^(+)+2e^(-)` `2H^(+)+2e^(-)toH_(2)` `2H_(HB)^(+)to2H_(HA)^(+)" "E^(@)=0` `E=0-(0.0591)/(2)log(([H^(+)]_(HA)^(2))/([H^(+)]_(HB)^(2)))` But `Ka=([H^(+)]^(2))/(c)` `=-(0.0591)/(2)log((10^(-3)xxC)/(10^(-5)xxC))=-0.0591` the cell is constructed in reversed direction. `E_(cell)=0.0591"volt"`

6.	Cadmium amalgam is prepared by electrolysis of a solution of `CdCl_(2)` using a mercury cathode. Find how long a current of 5 ampere should be passed in order to prepare 12% Cd-Hg amalgam on a cathode of 2 g mercury. At mass of Cd=112.40.
Answer» Correct Answer - `t=93.65sec`. `Cd^(2+)+2e^(-)toCd` Cd required for 2 g of `Hg=(12xx2)/(88)=0.2727g` `t=(2xx96500xx2727)/(1124xx5)=93.65sec`.

7.	The number of electrons delivered at the cathode during electrolysis by a current of `1` ampere in 60 seconds is (charger on electron `= 1.60 xx 10^(-19)C`)A. `3.74xx10^(20)`B. `6.0xx10^(23)`C. `7.48xx10^(21)`D. `6.0xx10^(20)`
Answer» Correct Answer - A `Q="ne"=it` `n=(1xx60)/(1.6xx10^(-19))=3.74xx10^(20)`

8.	Which of the following statement is true for the electrochemical Daniell cell ?A. electrons flows from copper electrode to zinc electrode.B. Current flows from zinc electrode to copper electrode.C. Cations moves towards copper electrodes.D. cations moves towards zinc electrode.
Answer» Correct Answer - C Daniel cell is copper -zinc electrochemical cell where `Cu^(2+)` deposit at copper cathode.

9.	the standard reduction potenital of a silver chloride electrode is 0.2 V and that of a silver electrode is 0.79 V. The maximum amount of AgCl that can dissolve in `10^(6)`L of a 0.1 M `AgNO_(3)` solution is:A. 0.5 mmolB. 1.0 mmolC. 2.0 mmolD. 2.5 mmol
Answer» Correct Answer - B `AgCl+e^(-)toAgtoCl^(-)" "E^(@)=0.2V` `underline(AgtoAg^(+)+e^(-)" "E^(@)=-0.79V` `AgCloverset(e^(-))toAg^(+)+Cl^(-)" "E^(@)=-0.59V` `E^(@)=(0.059)/(n)logKimplies-0.59=(0.059)/(1)logK_(SP)impliesK_(SP)=10^(-10)` Now solubility of `AgCl` in 0.1 M `AgNO_(3)` `S(S+0.1)=10^(-10)impliesS=10^(-9)mol//L` Hence 1 mole dissolves in `10^(9)L` L solution. Hence in `10^(6)L` L amount that dissoves in 1 m mol.

10.	A cell `Cu\|Cu^(++)\|\|Ag^(+)\|Ag` initially contains `2MAg^(+)` and `2MCu^(++)` ions in 1 L electrolyte. The change in cell potential after the passage of 10 amp. Curret for 4825 sec is:A. `-0.00738V`B. `-1.00738V`C. `-0.0038V`D. none
Answer» Correct Answer - A `Q=10xx4825=48250C` no. of faraday `=(48250)/(96500)=0.5` `Ag+undersetunderset(2-0.25)(2.00)((1)/(2)Cu^(++))toundersetunderset(2+0.50)(2.00)(Ag^(+))+(1)/(2)Cu` `E_(cell)=E_(cell)^(@)-(0.0591)/(1)log(([Ag^(+)])/([Cu^(++)]^(1//2)))` `E_(1)=E_(cell)^(@)-(0.0591)/(1)log((2.00)/((2.00)^(1/2)))` `E_(2)=E_(cell)^(@)-(0.0591)/(1)log((2.50)/((1.75)^(1//2)))` `triangleE=E_(2)-E_(1)=(0.0591)/(1)[logsqrt(2)-log((2.50)/(sqrt(1.75)))]=(0.0591)/(1)[log1.41-log1.88]` `=(0.0591)/(1)[0.1492-0.2742]=-(0.0591)/(1)xx0.125=-0.00738V`.

11.	The equivalent conductivity of `KCl` at infinite dilution is `130S cm^(2) eq^(-1)`. The transport number of `Cl^(-)` ion in `KCl` at the same temperature is `0.505`. The limiting ionic mobility of `K^(+)` ion is :A. `6xx67xx10^(-4)cm^(2)sec^(-1)"volt"^(-1)`B. `5.01xx10^(-3)cm^(2)sec^(-1)"volt"^(-1)`C. `3.22xx10^(-4)cm^(2)sec^(-1)"volt"^(-1)`D. `2.00xx10^(-4)cm^(2)sec^(-1)"volt"^(-1)`
Answer» Correct Answer - A `(lamda_(cl^(-))^(@))/(lamda_(K^(+))^(@)+lamda_(Cl^(-))^(@))0.505` or `lamda_(Cl^(-))^(@)=0.505xx130approx65.65Scm^(2)eq^(-1)` `lamda_(K^(+))^(@)=FxxU_(K^(+))` or `U_(K^(+))=((130-65.65))/(96500)cm^(2)"volt"^(-1)sec^(-1)`

12.	Strong acid versus strong base: The principle of conductometric titrations is based on the fact that during the titration, one of the ions is replaced by the other and invariable these two ions differ in the ionic conductivity with the result that thhe conductivity of the solution varies during the course of the titration. take, for example, the titration between a strong acid, say HCl, and a string base, say NaOH before NaOH is added, the conductance of HCl solution has a high value due to the presence of highly mobile hydrogen ions. As NaOH is added, `H^(+)` ions are replaced by relatively slower moving `Na^(+)` ions. consequently the conductance of the solution decreases and this continues right upto the equivalence point where the solution contains only NaCl. Beyond the equivalence point, if more of NaOH is added, then the solution contains a excess of the fast moving `OH^(-)` ions with the result that its conductance is increased ad it condinues to increase as more and more of NaOH is added. If we plot the conductance value versus the amount of NaOH added, we get a curve of the type shown in Fig. The descending portion AB represents the conductances before the equivalence point (solution contains a mixture of acid HCl and the salt NaCl) and the ascending portion CD represents the conductances after the equivalence point (solution contains the salt NaCl and the excess of NaOH). The point E which represent the minium conductance is due to the solution containing only NaCl with no free acid or alkali and thus represents the equivalence point. this point can, however, be obtained by the extrapolation of the lines AB and DC, and therefore, one is not very particular in locating this point expermentally as it is in the case of ordinary acid-base titrations involving the acid-base indicators. Weak acid versus strong base: Let us take specific example of acetic acid being titrated against `NaOH`. Before the addition of alkali, the solution shows poor conductance due to feeble ionization of acetic acid. Initially the addition of alkali causes not only the replacement of `H^(+)` by `Na^(+)` but also suppresses the dissociation of acetic acid due to the common ion `Ac^(-)` and thus the conductance of the solution decreases in the beginning. but very soon the conductance start increasing as addition of NaOH neutralizes the undissociated HAc to `Na^(+)Ac^(-)` thus causing the replacement of non-conducting HAc with Strong-conducting electrolyte `Na^(+)Ac^(-)`. the increase in conductance continuous right up to the equivalence point. Beyond this point conductance increases more rapidly with the addition of NaOH due to the highly conducting `OH^(-)` ions, the graph near the equivalence point is curved due to the hydrolysis of the salt `NaAc`. The actual equivalence point can, as usual, be obtained by the extrapolation method. In all these graphs it has been assumed that the volume change due addition of solution from burrette is negnigible, hence volume change of the solution in beaker the conductance of which is measured is almost constant throughout the measurement. Q. The most appropriate titration curve obtained when a mixture of a strong acid (say HCl) and a weak acid (say `CH_(3)COOH`) is titrated with a strong base (say NaOH) will beA. B. C. D.
Answer» Correct Answer - C

14.	Acetic acid is titrated with NaOH solution. Which of the following statement is correct for this titration?A. Conductance increases upto equivalence point, then it decreasesB. Conductance increases upto equivalence point, then it increasesC. first conductance increases slowly upto equivalence point and then increases rapidlyD. first conductance increases slowly upto equivalence point ad then drops rapidly.
Answer» Correct Answer - C `CH_(3)COOH+NaOHtoNa^(+)+CH_(2)COO^(-)+H_(2)O` to conductance `I^(st)` increases slowly since no. of ions increases after end point it inceases sharply due to `OH^(-)` ions.

15.	Which statement is correct?A. A solution of copper (II) sulphate can be stored in iron vessel.B. An oxide layer on zinc vessel can be easily removed by washing with dilute `HCl`.C. Molten `PbBr_(2)` is good conductor of electricity because it contains free ions.D. in the reaction `Li+(1)/(2)H_(2)toLiH`, hydrogen is a reducing agent.
Answer» Correct Answer - C ionic compounds in molten state are conductor of electricity because of free ions.

16.	During the electrolysis of 0.1 M `CuSO_(4)` solution using coppepr electrodes, a depletion of `[Cu^(2+)]` occurs near the cathode with a corresponding excess near the anode, owing to inefficient stirring of the solution. If the local concentration of `[Cu^(2+)]` near the anode and cathode are respectively 0.12 M and 0.08 M, calcualte the back emf developed. Temperature = 298 K.A. 22 mVB. 5.2 mVC. 29 mVD. 59 mV
Answer» Correct Answer - B `E_(cell)=E_(cell)^(0)-(0.0591)/(2)log_(10)(([Cu^(2+)]_("cathode"))/([Cu^(2+)]_("anode")))` `E_(cell)^(0)=0` `E_(cell)=-(0.591)/(2)log_(10)((0.08)/(0.12))=+5.2V`.

17.	The molar conductance of NaCl varies with the concentration as shown in the following table and all values follows the equation. `lambda_(m)^(c)=lambda_(m)^(oo)-bsqrt(C)` where `lambda_(m)^(c)`= molar specific conductance `lambda_(m)^(oo)=` molar specific conductance at infinite dilution C=molar concentration When a certain conductivity cell (C) was filled with 25`xx10^(-4)(M) NaCl` solution, the resistance of the cell was found to be 1000 ohm. At infinite dilution, conductance of `Cl^(-)` and `SO_(4)^(2-)` are `80ohm^(-1) cm^(2) "mole"^(-1)` and `160ohm^(-1) cm^(2) "mole"^(-1)` respectively. What is the molar conductance of NaCl at infinite dilution?A. `147ohm^(-1)cm^(2)"mole"^(-1)`B. `107ohm^(-1)cm^(2)s"mole"^(-1)`C. `127ohm^(-1)cm^(2)"mole"^(-1)`D. `157ohm^(-1)cm^(2)"mole"^(-1)`
Answer» Correct Answer - C `lamda_(m)^(C)=lamda_(m)^(infty)-bsqrt(C)` when `C_(1)=4xx10^(-4)lamda_(m)^(C)=107` and when `C_(2)=9xx10^(-4),lamda_(m)=97` so `107=lamda_(m)^(infty)-bxx2xx10^(-2)` .(1) `97=lamda_(m)^(infty)-bxx3xx10^(-2)` ..(2) `b=1000` `lamda_(m)=lamda_(m)^(infty)-bsqrt(C)` `lamda_(m)^(infty)=lamda_(m)-bsqrt(C)=107+10^(3)xx2xx10^(-2)` `lamda_(m)^(infty)=127ohm^(-1)cm^(2)"mole"^(-1)`

18.	Statement-1: Copper is dissolved at anode and deposited at cathode when Cu electrodes are used and electrolyte is 1M `CuSO_(4)(aq)` solution. Statement-2: SOP of Cu is less than SOP of water and SRP of Cu is greater than SRP of water.
Answer» S.O.P of Cu is greater than S.O.P of water `(H_(2)OtoO_(2))` and S.R.P. of Cu is greater than S.R.P of water `(H_(2)OtoH_(2))`.

19.	The molar conductance of NaCl varies with the concentration as shown in the following table and all values follows the equation. `lambda_(m)^(c)=lambda_(m)^(oo)-bsqrt(C)` where `lambda_(m)^(c)`= molar specific conductance `lambda_(m)^(oo)=` molar specific conductance at infinite dilution C=molar concentration When a certain conductivity cell (C) was filled with 25`xx10^(-4)(M) NaCl` solution, the resistance of the cell was found to be 1000 ohm. At infinite dilution, conductance of `Cl^(-)` and `SO_(4)^(2-)` are `80ohm^(-1) cm^(2) "mole"^(-1)` and `160ohm^(-1) cm^(2) "mole"^(-1)` respectively. What is the cell constant of the conductivity cell (C)?A. `0.385cm^(-1)`B. `3.86cm^(-1)`C. `38.5cm^(-1)`D. `0.1925cm^(-1)`
Answer» Correct Answer - D For `25xx10^(-4)` (M) NaCl solution ltbr `lamda_(m)=lamda_(m)^(infty)-bsqrt(C)` `lamda_(m)=127-10^(3)(25xx10^(-4))^(1//2)` `lamda_(m)=127-10^(3)xx5xx10^(-2)` `lamda_(m)=77` but `lamda_(m)=(Kxx1000)/(M)`:`K=((l)/(a))xx(1)/(R))` `lamda_(m)=((l)/(a))xx(1)/(R)xx(1000)/(M)` `lamda_(m)=`[cell constant] `xx(1000)/(RxxM)implies77=`[cell constanta]`xx(1000)/(1000xx25xx10^(-4))` Cell constant `=77xx25xx10^(-4)=0.1925cm^(-1)`

20.	`2Ce^(4+) + Co rightarrow 2Ce^(3+) + Co^(2+), E_(cell)^(@) = 1.89V` `E_(Co^(2+)//Co)^(@) = -0.277V`. Hence `E_(Ce^(4+)//Ce^(3+))^(@)` isA. 0.805 VB. 1.62 VC. `-0.805 V`D. `-1.61 V`
Answer» Correct Answer - B `E_(cell)^(@)=1.89,E_(Ce^(4+)//Ce^(3+))^(@)+E_(Co//Co^(3+))^(@)+E_(Co//Co^(2+))^(@)=E+0.277impliesE=1.62V`

21.	Given : `E^(@) (Cu^(2+//Cu)` = 0.337V` and `E^(@) (Sn^(2+//Sn) = -0.136V`. Which of the following statements is correct?A. `Cu^(2+)` ions can be reduced by `H_(2)(g)`B. `Cu` can be oxidized by `H^(+)`C. `Sn^(2+)` ions can be reduced by `H_(2)(g)`D. `Cu` can reduce `Sn^(2+)`
Answer» Correct Answer - A As `E_(Ce^(+))^(@)toCu=0.337VgtE_(H^(+)//H_(2))^(0)` `therefore` `Cu^(2+)` can be reduced by `H_(2)`

23.	For ` Zn^(2+) //Zn, E^@ =- 0. 76 V`, for `Ag^+ //Af E^@ =0.799 V`. The correct statement is .A. The reaction Zn getting reduced Ag getting oxidized is spontaneousB. Z undergoes reduction and Ag is oxidizedC. Zn undergoes oxidation `Ag^(+)` gets reducedD. No suitable answer
Answer» Correct Answer - C Lower S.R.P containing ion ca displace higher S.R.P containing ion.

24.	The emf of the cell, `Zn\|Zn^(2+)(0.01M)\|\| Fe^(2+)(0.001M) \| Fe` at 298 K is 0.2905 then the value of equilibrium constant for the cell reaction is:A. `e^((0.32)/(0.0295))`B. `10^((0.32)/(0.0295))`C. `10^((0.26)/(0.0295))`D. `10^((0.32)/(0.059))`
Answer» Correct Answer - B `Zn\|Zn^(2+)(0.01M)\|\|Fe^(2+)(0.001M)\|Fe," "E=0.2905` cell reaction, `Zn+Fe^(2+)hArrZn^(2+)+Fe`. `0.2905=E^(@)-(0.0591)/(2)log((0.01)/(0.001)` `E^(@)=0.32"volt"` At equilibrium `E_(cell)=0` `0=0.32-(0.0591)/(2)logK_(eq)` `K_(eq)=10^(0.32//0.0295)`

25.	`K_(d)` for dissociation of `[Ag(NH_(3))_(2)]^(+)` into `Ag^(+)` and `NH_(3)` is `6 xx 10^(-8)`. Calculae `E^(@)` for the following half reaction. `AG(NH_(3))_(2)^(+) +e^(-) rarr Ag +2NH_(3)` Given `Ag^(+) +e^(-) rarr Ag, E^(@) = 0.799V`
Answer» Correct Answer - 0.373 V `[Ag(NH_(3))_(2)]^(+)toAg^(+)+2NH_(3),K_(d)=6xx10^(-8),triangleG_(1)^(0)=-RTln6xx10^(-8)` `underline(Ag^(+)+e^(-)toAg,)" "E^(@)=0.799"volt",triangleG_(2)^(@)=-1xx0.799xxF` `underline([Ag(NH_(3))_(2)]^(+)+e^(-)toAg(s)+)2NH_(3)," "triangleG^(@)=triangleG_(1)^(0)+triangleG_(2)^(0)` `-1xxE^(@)xxF=-RTln6xx10^(-8)-1xx0.799xxF` `E^(@)=0.373"volt"`

26.	Calculate the potential of an indicator electrode versus the standard hydrogen electrode, which originally contained `0.1M MnO_(4)^(-)` and `0.8M H^(+)` and which was treated with `Fe^(2+)` necessary to reduce `90%` of the `MnO_(4)` to `Mn^(2+)` `MnO_(4)^(-) +8H^(+) +5e rarr Mn^(2+) +H_(2)O, E^(@) = 1.51V`
Answer» Correct Answer - 1.39 V `{:(,MnO_(4)^(-),+,8H^(+),+,5e^(-),to,Mn^(2+),+,H_(2)O),("Initially",0.1,,0.8,,,,0,,0),("After reaction",0.1-0.1xx0.9,,0.8-0.09xx8,,,,0.09,,0.09),(,0.10-0.09,,0.8-0.09xx8,,,,0.09,,0.09),(,0.01,,0.08,,,,0.09,,0.09):}` `E=E^(@)-(0.059)/(5)log(([Mn^(2+)])/([MnO_(4)^(-)][H^(+)]^(8)))=1.51-(0.059)/(g)log_(10)(((0.09))/((0.01)(0.08)^(8)))=1.39V`

27.	Which of the following statements is wrong about galvanic cells?A. Cathode is the positive electrodeB. cathode is the negative electrodeC. electrons flow from cathode to anode in the external circuitD. reduction occurs at cathode
Answer» Correct Answer - B::C Reduction and electronation take place at cathode electrode, so it become positive electrode.

28.	Which of the following is/are function(s) of salt-bridge?A. it completes the electrical circuit with electrons flowing from one electrode to the other through external wires ad a flow of ions betwee the two compartments through salt-bridge.B. it minimises the liquid-liquid junction potentialC. both correctD. none of these
Answer» Correct Answer - C

29.	Salt bridge containsA. calomelB. corrosive sublimateC. `H_(2)O`D. agar-agar paste
Answer» Correct Answer - D Agar-agar is a gelatin, it used in salt bridge along with KCl electrolyte.

30.	The resistance of two electrolytes X and Y ere found to be 45 and 100 respectively when equal volumes of both the solutions were taken in the same cell in two different experiments. If equal volumes of these solutions are mixed in the same cell, what will be the conductance of the mixture?
Answer» Correct Answer - `0.016mhocm^(-1)` `K=(K_(1)+K_(2))/(2)impliesK=(1)/(2)((1)/(R_(1))+(1)/(R_(2)))impliesK=0.0165Scm^(-1)`

31.	The highest electrical conductivity of the following aqueous solutions is ofA. 0.1 M acetic acidB. 0.1 M chloroacetic acidC. 0.1 M fluoroacetic acidD. 0.1 M difluoroacetic acid.
Answer» Correct Answer - D Difluoroacetic acid will be strongest acid due to electron withdrawing effect of two fluoring atoms so as it will show maximum electrical conductivity.

33.	Name te factors which affect electrical conductivity of electrolytes.
Answer» (i). Nature of electrolyte. (ii). Concentration of ions in solution. (iii). Temperature.