 # Electrochemistry : Important Questions.

1.Calculate the potential of hydrogen electrode in contact with a solution whose pH is 10.

2. Calculate the emf of the cell in which the following reaction takes place:

Ni + 2 Ag(+) (0.002 M)= Ni(+2) (0.160 M)+ 2Ag Given that Eo = 1.05 V

3:The cell in which the following reactions occurs:

2Fe(+3) + 2I(-) = 2Fe(+2) + I2 Eo = 0.236 V at 298 K.  Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.

4:Why does the conductivity of a solution decrease with dilution?

5:The molar conductivity of 0.025 mol L−1 methanoic acid is  46.1 S cm2 mol−1.Calculate its degree of dissociation and dissociation constant. Given λ °(H+) = 349.6 S cm2 mol−1 λ °(HCOO−) = 54.6 S cm2 mol C = 0.025 mol L−1

6:If a current of 0.5 ampere flowsthrough a metallic wire for 2 hours, then how many electrons would flow through the wire?

7:What is the quantity of electricity in coulombs needed to reduce 1 mol of Cr2O7(-2) to Cr(+3).

8:Write the chemistry of rechargingthe lead storage battery, highlighting all the materials that are involved during recharging.

9:Suggest two materials other than hydrogen that can be used as fuels in fuel cells.Ans -  Methane and methanol can be used as fuels in fuel cells.

10:Calculate the standard cellpotentials of galvanic cells in which the following reactions take place: 2Cr(s) + 3Cd2+(aq) → 2Cr3+(aq) + 3Cd (ii) Fe2+(aq) + Ag+(aq) → Fe3+(aq) + Ag(s)

Eo (Cr) = 0.74 V , Eo(Cd) = -0.40 Calculate the ΔrGθ and equilibrium constant of the reactions  (

11:Write the Nernst equation and emfof the following cells at 298 K:

(i) Sn(s) | Sn2+(0.050 M) ||H+(0.020 M) | H2(g) (1 bar) | Pt(s)

(iii) Pt(s) | Br2(l) |Br(0.010 M) || H+(0.030 M) | H2(g) (1 bar) |Pt(s).

12:In the button cells widely used in watches and other devices the following reaction takes place:

Zn(s) + Ag2O(s) + H2O(l) → Zn2+(aq) + 2Ag(s) + 2OH(aq) Determine Gibbs energy for the reaction

13:Define conductivity and molar conductivity for the solution of an electrolyte. Discuss their variation with concentration.

14:The conductivity of 0.20 M solution of KCl at 298 K is 0.0248 Scm−1. Calculate its molar                     conductivity.Given,  κ = 0.0248 S cm−1 c = 0.20 Calculate for all concentrations and draw aplot between and c½. Find the value of.

15:Conductivity of 0.00241 M acetic acid is 7.896 × 10−5 S cm−1. Calculate its molar conductivity  and if molar conductivity at infinite dilution for acetic acid is 390.5 S cm2 mol−1, what is its dissociation constant?

Given,κ = 7.896 × 10−5 S m−1 c = 0.00241 mol L−1

16: How much electricity in terms ofFaraday is required to produce

(i) 20.0 g of Ca from molten CaCl2. (ii) 40.0 g of Al from molten Al2O3.

17:A solution of Ni(NO3)2 is electrolysed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode?

18: Three electrolytic cells A,B,Ccontaining solutions of ZnSO4, AgNO3 and CuSO4,respectively are connected in series. A steady current of 1.5 amperes was passed through them until 1.45 g of silver deposited at the cathode of cell B. How long did the current flow? What mass of copper     and zinc were deposited?

19:Predict the products ofelectrolysis in each of the following:

(i) An aqueous solution of AgNO3with silver electrodes.

(ii) An aqueous solution of AgNO3with platinumelectrodes.

(iii) A dilute solution of H2SO4withplatinum electrodes.

(iv) An aqueous solution of CuCl2 with platinumelectrodes.

20. What is meant by Fuel cell ? Also give itsreactions?

21.The conductivity of 0.001 M Acetic acid is  4.95 x 10-5 S cm- .  Calculate the dissociation constant. If molar   conductivity for  acetic acid at infinite dilution is 390.5  S cm2 mol-1  .

22.The conductivity of saturated soln of AgCl at 288K is found to be  1.382 x 10-6 S cm- . Find its solubility . Given ionic conductances of Ag+ & Cl-  at infinite dilution are 61.9  , 76.3 S cm2 mol-

23 .Find the charge in Coulombs on 1 g-ion of N-3.