Electrochemistry: Class 12 Previous Year Questions

Electrochemistry questions asked in CBSE board exams

Repeated questions first. Open the free app to see each question as it appeared in the paper, with its marking scheme.

1. (a) Calculate emf and G for the following cell at 298 K : 5 Mg(s) / Mg2+(0.01 M) // Ag+(0.001 M) / Ag(s) Given : E Mg2+ / Mg = –2.37 V E Ag+ / Ag = +0.80 V [ 1 F = 96500 C mol–1, log 10 = 1] OR (b) For the reaction : 5 2AgCl(s) + H2(g) (0.4 atm) — 2Ag(s) +…
   Board 20265 markslong answer
2. (A) (a) The conductivity of 0.1 mol L–1 solution of NaCl is 1.06 × 10–2 S cm–1. Calculate its molar conductivity and degree of dissociation. 3 + 2 °Na+ = 50.1 S cm2 mol–1 °Cl – = 76.5 S cm2 mol–1 (b) (i) Following cell reaction occurs in a galvanic cell : 2A…
   Board 20265 markslong answer
3. What will happen during the electrolysis of aqueous solution of CuCl2 by using platinum electrodes ? 1 (A) Cu will deposit at Anode (B) H2 gas will be released at cathode (C) O2 gas will be released at anode (D) Cl2 gas will be released at anode { } 6 6. …
   Board 20261 markMCQ
4. (a) Answer the following : 3  1 (i) Why is the Equilibrium Constant (Kc) related to E cell and not to Ecell ? (ii) Two metals ‘A’ and ‘B’ have standard electrode potential values of –0.24 V and +0.80 V respectively. Which of these will liberate hydrogen gas …
   Board 20263 marksshort answer
5. (A) 31. (a) Write the cell reaction and calculate the e.m.f. of the following cell at 298 K : (3 + 2 = 5) Sn(s) ISn2+ (0.004 M) IIH+ (0.02 M) IH2(g) (1 Bar) IPt (s) · 19 (b) 1 HO () 31.(B) (a) (2 + 3 = 5) (b) ()+H -01 × 0' ()+g 10'0 (b)*3 0'0 Cr20(aq) + 14H+(a…
   Board 20255 markslong answer
6. The electrical resistance of a column of 0.05 M NaOH solution of area 0.8 cm2 and length 40 cm is 5 × 103 ohm. Calculate its resistivity, conductivity and molar conductivity.
   Board 20253 marksshort answer
7. (A) (a) Calculate the standard Gibbs energy (A,G°) of the following reaction at 25 °C : 3 + 2 Au(s) + Ca2+(1M) · Au3+(1M) + Ca(s) = - 2.87 V [1 F = 96500 C mol-1] (b) Tarnished silver contains Ag2S. Can this tarnish be removed by placing tarnished silverware i…
   Board 20255 markslong answer
8. State the following : (a) 23. (i) Kohlrausch law of independent migration of ions and (ii) Faraday's first law of electrolysis. (b) Using Evalues of X and Y given below, predict which is better for values coating the surface of iron to prevent corrosion and wh…
   Board 20253 marksshort answer
9. Standard electrode potential for Sn4+/Sn2+ couple is +0.15 V and that for the Cr3+/Cr couple is -0.74 V. The two couples in their standard states are connected to make a cell. The cell potential will be (A) +1.19V (B)+0.89 V (C)+0.18 V (D) +1.83 V
   Board 20251 markMCQ
10. Assertion (A) : Cu cannot liberate H, on reaction with dilute mineral acids. Reason (R) : Cu has positive electrode potential.
    Board 20251 markAssertion-Reason
11. (H$) (i) 0 05 M CH3COOH [db`Z H$m à{VamoY 100 Amo_ nm`m J`m & `{X gob pñWam§H$ 0 0354 cm 1 h¡, Vmo Eogr{Q>H$ Aåb {db`Z H$s _moba MmbH$Vm n[aH${bV H$s{OE & (ii) \¡$amS>o Ho$ {dÚwV-AnKQ>Z H$m àW_ {Z`_ {b{IE & 1 _mob 4 MnO H$mo Mn2+ _| AnM`Z Ho$ {bE \¡$amS>o _| {…
    Board 20245 markslong answer
12. During electrolysis of aqueous solution of NaCl : (A) H2 (g) is liberated at cathode (B) Na is formed at cathode (C) O2 (g) is liberated at anode (D) Cl2 (g) is liberated at cathode 8 11. amgm`{ZH$ A{^{H«$`m {b{IV _mÌmAm| _| go {H$gH$mo n[ad{V©V H$a XoVm h¡ ? …
    Board 20241 markMCQ
13. Calculate the potential of Iron electrode in which the concentration of Fe2+ ion is 0·01 M. (E o Fe2+/Fe = 0·45 V at 298 K) [Given : log 10 = 1]
    Board 20242 marksshort answer
14. (a) Conductivity of 2  10–3 M methanoic acid is 8  10–5 S cm–1. Calculate its molar conductivity and degree of dissociation if o m for methanoic acid is 404 S cm2mol–1. 3 + 2 (b) Calculate the rG and log Kc for the given reaction at 298 K : Ni(s) + 2Ag+ (…
    Board 20235 markslong answer
15. (H$) (i) Am`Zm| Ho$ ñdV§Ì A{^J_Z H$m H$mobamD$e {Z`_ {b{IE & H$mobamD$e {Z`_ Ho$ AZwgma Eogr{Q>H$ Aåb H$s gr_m§V _moba MmbH$Vm Ho$ {bE ì`§OH$ {b{IE & (ii) 298 K na Xr JB© A{^{H«$`m Ho$ {bE A{YH$V_ H$m`© Am¡a log Kc n[aH${bV H$s{OE : Ni (s) + 2Ag+ (aq) Ni2+ (aq…
    Board 20235 markslong answer
16. (a) Give reasons : 2  1 (i) Mercury cell delivers a constant potential during its life time. (ii) In the experimental determination of electrolytic conductance, Direct Current (DC) is not used. OR (b) Define fuel cell with an example. What advantages do the f…
    Board 20232 marksshort answer
17. Which of the following solutions of KCl will have the highest value of molar conductivity ? 1 (a) 0.01 M (b) 1 M (c) 0.5 M (d) 0.1 M
    Board 20231 markMCQ
18. Assertion (A) : Conductivity decreases with decrease in concentration of electrolyte. 1 Reason (R) : Number of ions per unit volume that carry the current in a solution decreases on dilution.
    Board 20231 markAssertion-Reason
19. Write the Nernst equation for the following cell reaction : Zn(s) + Cu2+ (aq) · Zn2+ (aq) + Cu(s) How will the Ecel be affected when concentration of (i) Cu2+ ions is increased and (i) Zn2+ ions is increased ? 1 ×2=2
    Board 20221 markvery short
20. Two statements are given below - one labelled Assertion (A) and the other labelled Reason (R). Assertion (A): Copper does not form copper (II) sulphate on reaction with dil. sulphuric acid. Reason (R): The standard potential for Cu+2|Cu electrode is negative. …
    CBSE practice 2023-241 markAssertion-Reason

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