Electrochemistry is concerned with chemical reactions that generate electricity as well as the changes caused by the passage of electrical current through matter. Because the reactions involve electron transfer, they are classified as oxidation-reduction (or redox) reactions. All electrochemical systems involve electron transfer in a reacting system. In many systems, the reactions take place in a region known as the cell, where electrons are transferred at electrodes.
Download Class 12 Chemistry Worksheet on Chapter 3 Electrochemistry Set 4 PDF.
CBSE Class 12 Chemistry Chapter 3 Electrochemistry Worksheet – Set 4
Q-1: Consider the electrochemical cell
M(s) | MI2(s) | MI2(aq) | M(s)
Where ‘M’ is a metal. At 298 K, the standard reduction potentials are Eo(M2+(aq)/M(s))= -0.12 V,
Eo(MI2(s)/M(s))= -0.36V and the temperature coefficient is 1.5×10-4 VK-1. At this temperature the standard enthalpy change for the overall cell reaction, ΔrHo is ______kJ/mol. (Round off to two decimal places) (Faraday constant F = 96500 C/mol)
Q-2: Define the term “electrochemical cell.” What happens if the applied external potential exceeds the E0cell of an electrochemical cell?
Q-3:Consider the diagram and respond to the following questions.
a) Which is cathode and which is anode?
b) What will happen if the salt bridge is removed?
c) What is the direction of electron flow?
Q-4: At infinite dilution, the equivalent conductance of CH3COONa, HCl and CH3COOH are 91, 426 and 391 mho cm2 respectively at 25oC. The eq. conductance of NaCl at infinite dilution will be ( in S cm2 eq-1)
- 126
- 209
- 391
- 908
Q-5: Given: Eo(I2/I–)= +0.54 V; Eo(Br2/Br–)= +1.09V; Eo(Fe2+/Fe)= -0.44 V
Which of the following reaction is non spontaneous?
a) Fe(s) + I2 → Fe2+ + 2I–
b) Br2 +2I– → 2Br– + I2
c) Fe(s) + Br2 → Fe2+ +2Br–
d) I2 + 2Br– → 2I– + Br2
Q-6: The molar conductance of 0.012 mol dm-3 aqueous solution of chloroacetic acid is 100 ohm-1 cm2 mol-1. The ion conductance of chloroacetate and H+ ions are 50 ohm-1cm2 mol-1 and 350 ohm-1cm2 mol-1 respectively. Calculate
i) degree of dissociation
ii) Ka of chloroacetic acid
iii) H+ ion concentration of solution
Q-7: The resistance of a 0.2 M electrolyte solution is 50 Ω. The specific conductance of a 0.2 M solution of the same electrolyte is 1.4 S m-1, while the resistance of a 0.5 M solution of the same electrolyte is 280 Ω. Calculate the molar conductivity of a 0.5 M electrolyte solution in S m2 mol-1.
Q-8: In the electrolytic cell, flow of electrons is from
- Cathode to anode in solution
- Cathode to anode through internal supply
- Cathode to anode through external supply
- Anode to cathode through internal supply
Q-9: Why can’t Na be obtained through electrolysis of aqueous NaCl solution?
Q-10: For the reaction, 2Cl(g) →Cl2(g)
The thermodynamic properties
a) ΔG, ΔH and ΔS are positive
b) ΔG, ΔH and ΔS are negative
c) ΔG, ΔH are negative and ΔS is positive
d) ΔG is negative and ΔH, ΔS are positive
Q-11: Define the term corrosion. What is rust’s chemical formula?
Q-12: What is a lead storage battery? In the operation of a lead storage battery, write the anode and cathode reactions as well as the overall cell reaction.
Q-13: A copper-silver cell is being constructed. The concentration of copper ions is 0.10 M.The composition of silver ions is unknown. When the cell potential was measured, it was 0.422 V. Determine the silver ion concentration in the cell.
Given: Eo(Ag+/Ag)= +0.80V, Eo(Cu2+/Cu)= +0.34V)
Q-14: CuSO4 solution is treated with KCl and KI separately. In which case will Cu2+ be reduced to Cu+?
a) with KCl
b) with KCl and KI both
c) with KI
d) None of the above
Q-15: On passing 0.1F of electricity through aluminium, metal deposited on cathode is(Al=27)
- 0.3 g
- 0.6 g
- 0.9 g
- 1.2 g
Q-16: Which of the following is correct?
a) Tl3+ salts are strong reducing agents.
b) Ge+ undergoes self oxidation in aqueous solution
c) In boron,+1 oxidation state is more stable
d) In+ undergoes self oxidation and reduction in aqueous solution
Q-17: The standard potential of a Daniel cell is +1.10 V and the equilibrium constant for the cell reaction is 1.5 ×1037. It can be concluded that
a) Zinc oxidises copper
b) Displacement of Cu by Zinc goes to near completion
c) Copper oxidises zinc
d) Displacement of zinc by copper goes to completion
Q-18: Match the Column I with Column II
| Column I | Column II |
|---|---|
| P. (C2H5)3N +CH3COOH | 1. Conductivity decreases and then increases |
| Q. KI(0.1 M) + AgNO3(0.01 M) | 2. Conductivity decreases and then does not change much |
| R. CH3COOH + KOH | 3. Conductivity increases and then does not change much |
| S. NaOH +HI | 4. Conductivity does not change much and then increases |
Q-19: Chromium metal can be plated out from an acidic solution containing CrO3 according to the following equation:
CrO3(aq) + 6H+(aq)+ 6e– → Cr(s) + 3H2O
Calculate
i) How many grams of chromium will be plated out by 24,000C?
ii) How long will it take to plate out 1.5 g of chromium by using 12.5 A current? (Molar mass of chromium = 52 g)
Q-20: Shyam purchased an old dry cell. He puts it in the torch. The torch didn’t light up. He discovered that the cell was dead.
(a) Why did this happen?
(b) Write the overall cell reaction during discharge.
(c) Why are dry cells not rechargeable?
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