Title 2B ELECTRO CHEMISTRY FINAL (VIJ) FINAL.pdf ✅

ELECTRO CHEMISTRY JEE ADVANCED NISHITH Multimedia India (Pvt.) Ltd., 6 1 JEE ADVANCED - VOL - VI REDOX REACTIONS & ELECTROCHEMISTRY NISHITH Multimedia India (Pvt.) Ltd., LEVEL - VI SINGLE ANSWER QUESTIONS 1. Given the overall formation constant of the [Fe(CN)6 ] 4- ion as 1035 and the standard potentials for the half reactions,     3 2 Fe e Fe  ;E° = 0.77 V     3 4 6 6 [Fe(CN) ] e [Fe(CN) ]  ; E° = 0.36 V Calculate the overall formation constant of the [Fe(CN)6 ] 3- ion. (A) 41 8.59 10  (B) 41 7.59 10  (C) 41 5.59 10  (D) 41 9.59 10  2. For reaction, 3 2 2Fe (aq) 2I (aq) 2Fe (aq) I (s) 2       has o E 0.236V cell  at 298 K. Thestandard Gibbs energy and the equilibrium constant of the cell reaction (A) 45.55 kJ/mol, 8.5  108 (B) 50.12 kJ/mol, 7.2  107 (C) - 50.12 kJ/mol, 8.5  108 (D) -45.55 kJ/mol, 9.6  107 3. The molar conductivity of 0.025 mol L-1 methanoic acid is 46.1 S cm2 mol-1. Its degree of dissociation( ) and dissociation constant. Given o (H )   = 349.6 S cm2 mol-1 and o (HCOO )   = 54.6 S cm2 mol-1 . (A) Ka = 3.67  104  =0.214 (B) Ka = 3.67  10-4  =0.114 (C) Ka = 2.25  10-4  =0.150 (D) Ka = 2.25  10-2  =0.314 4. An alloy of Pb-Ag weighing 1.08 g was dissolved in dilute HNO3 and the volume made to 100 mL.A ? silver electrode was dipped in the solution and the emf of the cell set-up as Pt (s), H2 (g) | H+ (1 M) || Ag+ (aq.) | Ag (s) was 0.62 V. If o Ecell is 0.80 V, what is the percentage of Ag in the alloy? (At 25°C, RT/F = 0.06) (A) 25 (B) 2.50 (C) 10 (D) 50 5. Consider the standard reduction potentials (in volts) as shown in figure. Find E° 2 2 2 0.936 0.576 4 3 2 3 o 1 SO SO S O 2 |__________ E ?____________          (A) -0.326 V (B) -0.425 V (C) -0.756 V (D) -0.512 6. Calculate the emf of the cell Pt, H2 (1.0 atm) | CH3COOH (0.1 M) || NH3 (aq, 0.01 M) | H2 (1.0 atm), Pt, Ka (CH3COOH) = 1.8  10-5 , kb (NH3 ) = 1.8  10-5 (A) -0.92 V (B) -0.46 V (C) -0.35 V (D) -0.20 V 7. In two vessels each containing 500 ml water, 0.5 m mol of aniline (Kb = 10-9) and 25 m mol of HCl are added separately. Two hydrogen electrodes are constructed using these solutions. Calculate the emf of cell made by connecting them appropriately. (A) 0.395 V (B) 0.792 V (C) 0.452 V (D) 0.312 V 8. Construct the cell corresponding to the reaction: 3Cr2+(1M)  2Cr3+(1M)+ Cr(s) and predict if the reaction is spontaneous. Also calculate the following i) Hand S of the reaction at 25°C. Given 3 o Cr ,Cr E  = 0.5 V, 3 2 o Cr ,Cr E   = - 0.41 V Gof the reaction at 35°C = - 270.50 kJ (A) 1 H 51.05 kJ, S 700kJ K      (B) 1 H 31.05 kJ, S 700kJ K      (C) 1 H 51.05 kJ, S 706kJ K      (D) 1 H 53.05 kJ, S 706kJ K      9. For the reaction,            2 2 - - 4 4Al s + 3O g + 6H O +4OH 4 Al OH ; 0 E = 2.73V cell . If   0 - -1 ΔG OH = -157kJmol f and   0 -1 ΔG H O = -237.2kJmol f 2 , determine  Al OH   4  0  ΔG f A) 3 1 1.30 10 kJ mol   B) 3 1 1.30 10 kJ mol    C) 3 1 3.30 10 kJ mol   D) 3 1 3.30 10 kJ mol   
REDOX REACTIONS & ELECTROCHEMISTRY 6 2 NISHITH Multimedia India (Pvt.) Ltd., JEE ADVANCED - VOL - VI NISHITH Multimedia India (Pvt.) Ltd., 10. For the galvanic cell Ag | AgCl(s), KCl(0.2 M) || KBr(0.001 M), AgBr(s) | Ag Find the EMF generated and assign correct polarity to each electrode for a spontaneous process after taking into account the cell reaction at 25°C. [Ksp (AgCl) = 2.8  10-10; Ksp (AgBr) = 3.3  10-13] (A) 0.057 V (B) 0.021 V (C) -0.052 V (D) -0.037 V 11. Consider the reaction of extraction of gold from its ore Au + 2CN– (aq.) + 4 1 O2 (g) + 2 1 H2O Au  2 (CN) + OH– Use the following data to calculate 0 G for the reaction Kf {Au  2 (CN) } = X O2 + 2H2O + 4e–  4OH– ;E° = + 0.41 volt Au3+ + 3e– Au ;E° = + 1.5 volt Au3+ + 2e– Au+ ;E° = + 1.4 volt (A) – RT ln X + 1.29 F (B) – RT ln X – 2.11 F (C) – RT ln X 1 + 2.11 F (D) – RT ln X – 1.29 F 12. A hydrogen electrode X was placed in a buffer solution of sodium acetate and acetic acid in the ratio a : b and another hydrogen electrode Y was placed in a buffer solution of sodium acetate and acetic acid in the ratio b : a. If reduction potential values for two cells are found to be E1 and E2 respectively w.r.t. standard hydrogen electrode, the pKa value of the acid can be given as (A) 0.118 E1  E2 (B) 0.118 E2  E1 (C) 0.118 E1  E2  (D) 0.118 E1  E2 13. A saturated solution in AgA (Ksp = 3×10–14) and AgB (Ksp = 1×10–14) has conductivity of 375 × 10–10 Scm–1 and limiting molar conductivity of Ag+ and A ̄ are 60 Scm2 mol– 1 and 80 Scm2 mol–1 respectively then what will be the limiting molar conductivity of B ̄ (in Scm2 mol–1) (A) 150 (B) 180 (C) 190 (D) 73 14. The standard emf of the cell, 2 0.1M Cd(s)| CdCl (aq) || AgCl(s) | Ag(s) in which the cell reaction is 0.6195 V at 0°C and 0.6753 V at 25° C. The value of H of the reaction at 25°C is (A) 167.26 kJ/mol (B)-167.26 kJ/mol (C) 40 K/mol (D) -40 Kcal/mol 15. The standard electrode potentials, 2 2 o o I / I Br / Br E , E   and 2 o Fe/ Fe E  are respectively + 0.54V, – 1.09 V and 0.44V as the basis of given data which of following is/are spontaneous (A) Br 2I 2Br I 2 2      (B) 2 Fe Br Fe 2Br 2      (C) 2 Fe I Fe 2I 2      (D) 2 2 I 2Br 2I Br      16. In which of the following (Ecell – Eo cell) = 0 (A) Zn |Zn2+ (0.01 M)| |Ag+ (0.1 M) |Ag(s) (B) Pt |H2 (1 atm)| pH=1| |Zn2+ (0.01 M) |Zn (C) Pt |H2 (1 atm)| pH=1| |Zn2+ (1 M) |Zn (D) Pt |H2 (1 atm)| H+ (0.01 M)| |Zn2+(0.01 M) |Zn 17. Select the correct statements if 9.65 ampere current is passed for 1 hour through the cell 2 1M 1M Ag | Ag || Cu | Cu   (A) Ag will oxidise to Ag and new Ag 1.36M       (B) Ag will reduce to Ag and new Ag 0.64M       (C) 2 Cu  will reduce to Cu and new 2 Cu 0.82M       (D) Cu will oxidise to 2 Cu  and new 2 Cu 0.82M      
ELECTRO CHEMISTRY JEE ADVANCED NISHITH Multimedia India (Pvt.) Ltd., 6 3 JEE ADVANCED - VOL - VI REDOX REACTIONS & ELECTROCHEMISTRY NISHITH Multimedia India (Pvt.) Ltd., 18. The electrolysis of acetate solution produces ethane according to reaction :   3 2 6 2 2 2 2 CH COO C H g e CO      The current efficiency of the process is 80%. What volume of gases would be produced at 0 27 C and 740 torr, if the current of 0.5 amp is passes through the solution for 96.45 min? (A) 6.0L (B) 0.60 L (C) 1.365 L (D) 0.91 L 19. 100 mL of 0.05 M CuSO4 aq solution was electrolyzed using inert electrodes by passing current till the pH of the resulting solutin was 2. The solution after electrolysis was neutralized and then treated with excess KI and formed 2 I titrated with 0.04 M Na S O 2 2 3 Calculated the required volume in mL of Na S O 2 2 3 (A) 112.5mL (B) 100 mL (C) 125 mL (D)150mL 20. What is the potential of an electrode which originally contained 0.1 M NO3  and 0.4M H  and which has been treated by 80% of the cadmium necessary to reduce all the NO3  to NO g  at 1 bar? Given : 3 2 NO H e NO H O 4 3 2 ;        0 E V   0.96 ;log 2 0.3 (A) 0.84 V (B) 1.08 V (C) 1.23 V (D) 1.36 V MULTI ANSWER QUESTIONS 21. When a galvanic cell starts operating, with passage of time, a) spontaneous character of the cell decreases, Ecell decreases b) reaction quotient 'Q' decreases, Ecell increase c) Useful work obtainable from the cell increases d) as cell stops producing voltage, Q= K. 22. Rusting on the surface of iron involves : a)     2 Fe s Fe aq e2     (at anodic site) b) O g H aq e H O l 2 2   4 4 2          (at cathodic site) c)       2 2 2 4 4 Fe aq O g H O l      2 3 2 8 Fe O s H    d) Fe O s xH O l Fe O x H O 2 3 2 2 3 2       . 23. Select the correct statement(s) regarding ref- erence electrodes a) Standard hydrogen electrode (SHE) is used as a primary reference electrode b) calomel electrode is used as a secondary ref- erence electrode c) calomel electrode is reversible with respect to chloride ion d) quinhydrone electrode is also used as a refer- ence electrode 24. Indicate the correct statements : a) conductivity cells have cell constant values indpendent of the solution filled into the cell b) In electro chemical cell, a salt bridge is used to maintain elctrical neutrality in each solutions c) Kohlrausch law is valid for both strong and weak electrolytes d) The k decreases but M E   and increase on dilution 25. Which of the following statements is/are cor- rect ? a) The conductance of one cm3 (or 1 unit3 ) of a solution is called specific conductance b) Specific conductnace increases while molar conductivity decreases on progressive dilution c) The limiting equivalent conductivity of wak electrolyte cannot be determine exactly by extraplotation of the plot of Aeq against c d) The conductance of metals is due to the mo- ment of free electrons
REDOX REACTIONS & ELECTROCHEMISTRY 6 4 NISHITH Multimedia India (Pvt.) Ltd., JEE ADVANCED - VOL - VI NISHITH Multimedia India (Pvt.) Ltd., 26. When a concentrated solution of an electro- lyte is diluted ? a) its specific conductance decreases b) its equivalent conductance increases c) its specific conductance increases and equiva- lent conductance decreases d) both specific and equivalent conductance de- creases 27. Given that 2+ 2+ 0 0 Ni / Ni Cu / Cu E = -0.25 V ;E = + 0.34 V; + 2+ - 0 0 Ag / Ag Zn / Zn E = + 0.80 V; E = -0.76 V . Which of the following redox processes will not take place in specified direction ? a)         2+ 2+ Ni aq + Cu s Ni s +Cu aq  b)         + 2+ Cu s +2Ag aq Cu aq +2Ag s  c)         + 2+ Cu s +2H aq Cu aq + H g  2 d)         + 2+ Zn s + 2H aq Zn aq + H g  2 28. Which of the following statement is correct? If 2 2 0 0 0.34 , 0.136 Cu Cu Sn Sn E V E V     and 2 0 0.0 H H E V    a) Cu ions can be reduced by H g 2   b) Cu can be oxidized by H  C) 2 Sn  ions can be reduced by H2 29. 2 amperes of current is passed for 16 min and 5 seconds through 1000 ml of 2 molar aqueous solution of CuSO4 using Pt elec- trodes. Then a) 1.2046 x 1022 electrons are passed from an- ode to cathode b) 0.635 g of Cu is deposited at cathode c) After the electrolysis process, when methyl orange is added to the residual solution, it gives yellow colour d) The volume of O2 gas liberated at anode is equal to the O2 liberated by the decomposition of 56 ml of 2 volume H2O2 solution at STP 30. For the cell,     2 0 / 0.001 || 0.1 | , Tl Tl M Cu M Cu Ecell   at 250C is 0.83V, which can be increased a) by increasing [Cu+2] b) by increasing [Tl+ ] c) by decreasing [Cu+2] d) by decreasing [Tl+ ] 31. For the cell at 298 K Ag(s) |AgCl(s) | KCl aq| |AgNO3 (aq)| Ag(s) Which of the following is wrong a) The EMF of the cell is zero when [Ag+]anodic = (Ag+ ) cathodic b) The amount of AgCl(s) precipitate in anodic compartment will decrease with the working of the cell c) The concentration of [Ag+ ] is constant in an- odic compartment with the working of cell d) 0 0 / / / cell Ag Ag Cl Ag Cl Ag E E E     0.059 1 log 1 Cl      anodic COMPREHENSION TYPE QUESTONS Comprehension -I The potential of an electrode when each species involved in it exists in the standard state is called its standard potential. The standard reduction potential of a couple is the measure of its tendency to get reduced. A series obtained by arranging the various couples in order of their decreasing standard potential is called electrochemical series. Any of the two couples of this series joined together gives an electrochemical cell in which reduction occurs at the electrode which occupiesthe higher position. The standard potential of hydrogen electrode is taken to be zero by convention.Given below are the sequence of half-reactions (acidic media) with relevant E0 values in volt at 298K.           0.560 2.26 2 4 4 0.95 1.50 3 2 2 1.18 MnO MnO MnO Mn Mn Mn Also given some more data are: 2 3 0.44 0.036 Fe Fe Fe (s)      