The study of the relationship between electrical energy and chemical changes in redox reactions is known as electrochemistry. Chemical energy is converted to electrical energy as a result of spontaneous redox reactions. Electrical energy can be used to convert non-spontaneous redox reactions into redox reactions.
Download Class 12 Chemistry Worksheet on Chapter 3 Electrochemistry Set 5 PDF.
CBSE Class 12 Chemistry Chapter 3 Electrochemistry Worksheet – Set 5
Q-1: Given below are the half-cell reactions,
Mn2++ 2e– → Mn ; Eo= -1.18 V
Mn3+ + e– → Mn2+ ; Eo=+1.51V
Calculate the Eo for 3Mn2+ →2Mn3+ + Mn. Is the reaction spontaneous or non spontaneous?
Q-2: Eo for Fe2++2e– → Fe is -0.44V and Eo for Zn2++2e– → Zn is -0.76V, thus
a) Fe is more electropositive than Zn
b) Zn is more electropositive than Fe
c) Zn is more electronegative
d) Fe is more electronegative
Q-3: Which of the following 0.1M aqueous solution has the highest electrical conductivity?
a) acetic acid
b) chloroacetic acid
c) difluoro acetic acid
d) fluoro acetic acid
Q-4: When an electric current is passed through acidulated water, 112mL of hydrogen gas at STP gets collected at cathode in 965 seconds. The current passed in amperes is
a) 1
b) 2
c) 0.5
d) 0.1
Q-5: Inert electrodes are used to electrolyze a sodium sulphate solution in water. The cathode and anode products are, respectively:
a) H2 and O2
b) O2 and H2
c) O2 and Na
d) SO2 and H2
Q-6: Which one of the following metals could not be obtained on electrolysis of aqueous solutions of its salts?
a) Mg
b) Ag
c) Cu
d) Cr
Q-7: The Zn2+|Zn half cell (Eo= -0.762 V) is connected to a Cu2+|Cu half cell (Eo = 0.34 V). What is the value of Eocell for spontaneous conversion of chemical energy to electrical energy? What is the value of log10K, where K is the equilibrium constant? (Use 2.303RT/F = 0.06)
Q-8: Clean electrical energy is provided by fuel cells in a variety of applications, including automobiles and stationary power sources. Hydrogen normally combines with oxygen to produce electrical energy and water. When we substitute butane for hydrogen at 1.0 bar and 298 K, the following reaction occurs:
C4H10(g) + 13/2 O2(g) → 4CO2(g) + 5H2O(l)
If the change in the Gibbs free energy of this reaction is 2746.06 kJ/mol, involving 26 electrons. Calculate the open circuit voltage.
a) +1.55 V
b) -1.09 V
c) 3.15 V
d) 2.06 V
Q-9: If the Eocell for a given reaction has a negative value, which gives the correct relationships for the values of ΔGo and Keq?
- ΔGo >0; Keq<1
- ΔGo >0; Keq>1
- ΔGo <0; Keq>1
- ΔGo <0; Keq<1
Q-10: An aqueous solution containing one mole per litre each of Cu(NO3)2,AgNO3, Hg2(NO3)2, Mg(NO3)2 is being electrolysed by using inert electrodes. The value of standard potentials are
Eo(Ag+/Ag) = 0.80 V , Eo(Hg2+2/Hg)= 0.79 V, Eo(Cu2+/Cu) = 0.34 V and Eo(Mg2+/Mg) = -2.3 V
With increasing voltage, find the correct sequence of deposition of metals on the cathode..
Q-11: Estimate the minimum potential difference needed to reduce Al2O3 at 500ºC. The free energy change for the decomposition reaction :
⅔ Al2O3 → 4/3 Al + O2 is ΔG = +960 kJ, F=96500 C/mol
Q-12: The EMF of the cell
Pt(s)|H2(1 atm) | H+ (a=x) || H+ (a=1)|H2(1 atm)| Pt(s) at 25oC is 0.59 V. Calculate the pH of the solution.
Q-13: Match the column I with column II
| Column I | Column I |
|---|---|
| A. ᴧm | 1. Intensive Property |
| B. Eocell | 2. Depends on number of ions/volume |
| C. 𝝹 | 3. Extensive property |
| D.ΔrGcell | 4. Increases with dilution |
Q-14: When the electric current is passed through a cell having an electrolyte, the positive ions move towards the cathode and negative ions towards the anode. If the cathode is pulled out of the solution
a) the positive and negative ions will move towards anode
b) the positive ions will start moving towards the anode while negative ions will stop moving
c) the negative ions will continue to move towards anode while positive ions will stop working.
d) the positive and negative ions will start moving randomly
Q-15: Equivalent conductivity of Fe2(SO4)3 is related to the molar conductivity by the expression:
a) ᴧeq=ᴧm
b) ᴧeq=ᴧm/3
c) ᴧeq= 3ᴧm
d) ᴧeq=ᴧm/6
Q-16: What is the molar conductivity of AgI at zero concentration if the 𝝀o value of NaI, AgNO3, NaNO3 are respectively 12 ohm-1cm2mol-1, 16 ohm-1cm2mol-1 and 10ohm-1cm2mol-1?
Q-17: In an electrochemical cell, EO(A2+/A)= -0.33 V, EO(B/B2+)= 0.50 V. Find ΔGO.
Q-18: Which of the following elements has the highest value of Eo(M2+/M)?
Ni, Mn, Cu, Fe
Q-19: Manganate ion disproportionate in neutral medium. Find the spin only magnetic moment of the species formed by the oxidation of manganate ion.(in B.M)
Q-20: Reena, a class XII Chemistry student, discovered that some kitchen wares made of iron or copper were galvanised.Reena advised her mother not to use these cookwares and to have them plated with tin rather than zinc.
(a) Why was Reena opposed to using zinc-plated cookware?
(b) What would happen if zinc-plated cookware was used in the kitchen?
(c) Can tin be used to plate the cookware?
(d) What values are associated with Reena’s advice?
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