Electrochemistry HOTs Class 12 Chemistry

HOTs for Class 12

Please refer to Electrochemistry HOTs Class 12 Chemistry provided below with solutions. All HOTs for Class 12 Chemistry with answers provided below have been designed as per the latest syllabus and examination petter issued by CBSE, NCERT, KVS. Students of Standard 12 Chemistry should learn the solved HOTS for Class 12 Chemistry provided below to gain better marks in examinations.

Electrochemistry Class 12 Chemistry HOTs

Question. When an aqueous solution of AgNO3 is electrolysed between platinum electrodes, the substances liberated at anode and cathode are
(a) silver is deposited at cathode and O2 is liberated at anode
(b) silver is deposited at cathode and H2 is liberated at anode
(c) hydrogen is liberated at cathode and O2 is liberated at anode
(d) silver is deposited at cathode and Pt is dissolved in electrolyte.

Answer

A

Question. For a cell reaction: Mn+(aq) + ne → M(s), the Nernst equation for electrode potential at any concentration measured with respect to standard hydrogen electrode is represented as

Electrochemistry HOTs Class 12 Chemistry
Answer

A

Question. The reaction which is taking place in nickel- cadmium battery can be represented by which of the following equation?
(a) Cd + NiO2 + 2H2O → Cd(OH)2 + Ni(OH)2
(b) Cd + NiO2 + 2OH– → Ni + Cd(OH)2
(c) Ni + Cd(OH)2 → Cd + Ni(OH)2
(d) Ni(OH)2 + Cd(OH)2 → Ni + Cd + 2H2O

Answer

A

Question. Electrical conductance through metals is called metallic or electronic conductance and is due to the movement of electrons. The electronic conductance depends on
(a) the nature and structure of the metal
(b) the number of valence electrons per atom
(c) change in temperature
(d) all of these.

Answer

D

Question. Mark the correct Nernst equation for the given cell.

Electrochemistry HOTs Class 12 Chemistry
Electrochemistry HOTs Class 12 Chemistry
Answer

C

Question. Following reactions are taking place in a Galvanic cell,
Zn → Zn2+ + 2e ; Ag+ + e → Ag
Which of the given representations is the correct method of depicting the cell?
(a) Zn(s) | Zn2+(aq) || Ag+(aq) | Ag(s)
(b) Zn2+ | Zn || Ag | Ag+
(c) Zn(aq) | Zn2+(s) || Ag+(s) | Ag(aq)
(d) Zn(s) | Ag+(aq) || Zn2+(aq) | Ag(s)

Answer

A

Question. A standard hydrogen electrode has a zero potential because
(a) hydrogen can be most easily oxidised
(b) hydrogen has only one electron
(c) the electrode potential is assumed to be zero
(d) hydrogen is the lightest element.

Question. At 25°C, Nernst equation is

Electrochemistry HOTs Class 12 Chemistry
Answer

A

Question. Given below are the standard electrode potentials of few half-cells. The correct order of these metals in increasing reducing power will be
K+|K = –2.93 V, Ag+|Ag = 0.80 V,
Mg2+|Mg = –2.37 V, Cr3+|Cr = –0.74 V.
(a) K < Mg < Cr < Ag
(b) Ag < Cr < Mg < K
(c) Mg < K < Cr < Ag
(d) Cr < Ag < Mg < K

Answer

B

Question. Mark the correct relationship from the foll1owing.
(a) Equilibrium constant is related to emf as

Electrochemistry HOTs Class 12 Chemistry
Electrochemistry HOTs Class 12 Chemistry
Answer

C

Question. During the electrolysis of dilute sulphuric acid, the following process is possible at anode.
(a) 2H2O(l) → O2(g) + 4H+(aq) + 4e
(b) 2SO2–4(aq) → S2O2–8(aq) + 2e
(c) H2O(l) → H+(aq) + OH(aq)
(d) H2O(l) + e → 1/2 H2(g) + OH(aq) 

Answer

A

Question. E° values of three metals are listed below.

Zn2+(aq) + 2e → Zn(s) ; E° = –0.76 V
Fe2+(aq) + 2e → 2Fe(s) ; E° = –0.44 V
Sn2+(aq) + 2e → Sn(s) ; E° = – 0.14 V
Which of the following statements are correct on the basis of the above information?
(i) Zinc will be corroded in preference to iron if zinc coating is broken on the surface.
(ii) If iron is coated with tin and the coating is broken on the surface then iron will be corroded.
(iii) Zinc is more reactive than iron but tin is less reactive than iron.
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i), (ii) and (iii)
(d) (i) and (iii)

Answer

C

Question. The specific conductivity of N/10 KCl solution at 20°C is 0.0212 ohm–1 cm–1 and the resistance of the cell containing this solution at 20°C is 55 ohm. The cell constant is
(a) 3.324 cm–1
(b) 1.166 cm–1
(c) 2.372 cm–1
(d) 3.682 cm–1

Answer

B

Question. Choose the option with correct words to fill in the blanks.According to preferential discharge theory, out of number of ions the one which requires _____ energy will be liberated ____ at a given electrode.
(a) least, first
(b) least, last
(c) highest, first
(d) highest, last

Answer

A

Question. ΔrG° for the cell with the cell reaction:
Zn(s) + Ag2O(s) + H2O(l) → Zn2+ (aq) + 2Ag(s) + 2OH(aq)

[E°Ag2O/Ag = 0.344 V, E°Zn2+/Zn = –0.76 V]
(a) 2.13 × 105 J mol–1
(b) –2.13 × 105 J mol–1
(c) 1.06 × 105 J mol–1
(d) –1.06 × 105 J mol–1

Answer

B

Question. E° value of Ni2+/ Ni is –0.25 V and Ag+ /Ag is +0.80 V. If a cell is made by taking the two electrodes what is the feasibility of the reaction?
(a) Since E° value for the cell will be positive, redox reaction is feasible.
(b) Since E° value for the cell will be negative, redox reaction is not feasible.
(c) Ni cannot reduce Ag+ to Ag hence reaction is not feasible.
(d) Ag can reduce Ni2+ to Ni hence reaction is feasible.

Answer

A

Question. What would be the equivalent conductivity of a cell in which 0.5 N salt solution offers a resistance of 40 ohm whose electrodes are 2 cm apart and 5 cm2 in area?
(a) 10 ohm–1 cm2 eq–1
(b) 20 ohm–1 cm2 eq–1
(c) 30 ohm–1 cm2 eq–1
(d) 25 ohm–1 cm2 eq–1 

Answer

B

Question. Which of the following is/are an application of electrochemical series?
(a) To compare the relative oxidising and reducing power of substances.
(b) To predict evolution of hydrogen gas on reaction of metal with acid.
(c) To predict spontaneity of a redox reaction.
(d) All of these

Answer

D

Question. Which of the given Nernst equation representation(s) is/are not correct for the given cell?

Electrochemistry HOTs Class 12 Chemistry

(a) I only
(b) I and III only
(c) II and IV only
(d) II, III and IV only

Answer

C

Question. The specific conductance of a saturated solution of AgCl at 25°C is 1.821 × 10–5 mho cm–1. What is the solubility of AgCl in water
(in g L–1), if limiting molar conductivity of AgCl is 130.26 mho cm2 mol–1?
(a) 1.89 × 10–3 g L–1
(b) 2.78 × 10–2 g L–1
(c) 2.004 × 10–2 g L–1
(d) 1.43 × 10–3 g L–1

Answer

C

Question. E° values for the half cell reactions are given below:
Cu2+ + e– → Cu+ ; E° = 0.15 V
Cu2+ + 2e– → Cu ; E° = 0.34 V
What will be the E° of the half-cell : Cu+ + e → Cu?
(a) +0.49 V
(b) +0.19 V
(c) +0.53 V
(d) +0.30 V

Answer

C

Question. Zn gives hydrogen with H2SO4 and HCl but not with HNO3 because
(a) Zn acts as oxidising agent when reacts with HNO3
(b) HNO3 is weaker acid than H2SO4 and HCl
(c) Zn is above the hydrogen in electrochemical series
(d) NO3 is reduced in preference to H+ ion. 

Answer

D

Question. When water is added to an aqueous solution of an electrolyte, what is the change in specific conductivity of the electrolyte?
(a) Conductivity decreases
(b) Conductivity increases
(c) Conductivity remains same
(d) Conductivity does not depend on number of ions.

Answer

A

Question. Jiya, a class-12 student recorded Λm of various electrolytes like acetic acid, sodium chloride and AlPO4, etc., at various concentrations. Then she plotted Λm versus √C . Graphs obtained by her are shown below:

Electrochemistry HOTs Class 12 Chemistry

Which of the given graph(s) is/are correct?
(a) I only
(b) I and II only
(c) I and III only
(d) I, II and III 

Answer

B

Question. Given below are two figures of Daniell cell
(X) and (Y). Study the figures and mark the incorrect statement from the following.

Electrochemistry HOTs Class 12 Chemistry

(a) In fig (X), electrons flow from Zn rod to Cu rod hence current flows from Cu to Zn (Eext < 1.1 V).
(b) In fig (Y), electrons flow from Cu to Zn and current flows from Zn to Cu (Eext > 1.1 V).
(c) In fig (X), Zn dissolves at anode and Cu deposits at cathode.
(d) In fig (Y), Zn is deposited at Cu and Cu is deposited at Zn. 

Answer

D

Question. Given below are few reactions with some expressions. Mark the expression which is not correctly matched.

Electrochemistry HOTs Class 12 Chemistry
Answer

B

Question. Arun, a class-12 student has a good habit of practicing the topic at home whichever taught in the class. After learning Nernst equation in class, he tried writing few Nernst equations for different cells. Next day when he shown the work to his class teacher she said all are correct except one.
The incorrect Nernst equation is

Electrochemistry HOTs Class 12 Chemistry
Answer

C

Question. The standard reduction potential for the half-cell reaction, Cl2 + 2e → 2Cl will be
(Pt2+ + 2Cl → Pt + Cl2 , E°cell = –0.15 V ;
Pt2+ + 2e → Pt, E° = 1.20 V)
(a) –1.35 V
(b) +1.35 V
(c) –1.05 V
(d) +1.05 V

Answer

B

Question. The half-cell reactions with their appropriate standard reduction potentials are
(i) Pb2+ + 2e → Pb ; E° = –0.13 V
(ii) Ag+ + e → Ag ; E° = +0.80 V
Based on the above data, which of the following reactions will take place?
(a) Pb2+ + 2Ag → 2Ag+ + Pb
(b) 2Ag + Pb → 2Ag+ + Pb2+
(c) 2Ag+ + Pb → Pb2+ + 2Ag
(d) Pb2+ + 2Ag+ → Pb + Ag

Answer

C

Question. In a cell reaction, Cu(s) + 2Ag+(aq) → Cu2+(aq)+ 2Ag(s)
E°cell = +0.46 V. If the concentration of Cu2+ ions is doubled then E°cell will be
(a) doubled
(b) halved
(c) increased by four times
(d) unchanged. 

Answer

D

Question. Units of the properties measured are given below. Which of the properties has not been matched correctly?
(a) Molar conductance = S m2 mol–1
(b) Cell constant = m–1
(c) Specific conductance = S m2
(d) Equivalent conductance = S m2 (g eq)–1

Answer

C

Question. The equivalent conductivity of N/10 solution of acetic acid at 25°C is 14.3 ohm–1 cm2 equiv–1.
What will be the degree of dissociation of acetic acid (ΛCH3COOH = 390.71 ohm–1 cm2 equiv–1)?
(a) 3.66%
(b) 3.9%
(c) 2.12%
(d) 0.008% 

Answer

A

Question. Which of the following is the cell reaction that occurs when the following half-cells are combined?
I2 + 2e → 2I (1 M) ; E° = +0.54 V
Br2 + 2e → 2Br– (1 M) ; E° = +1.09 V
(a) 2Br– + I2 → Br2 + 2I
(b) I2 + Br2 → 2I– + 2Br
(c) 2I– + Br2 → I2 + 2Br
(d) 2I– + 2Br– → I2 + Br2

Answer

C

Question. The process of chemical decomposition of the electrolyte by the passage of electricity through its melt or aqueous solution is called electrolysis.
The following apparatus is used for the electrolysis process:

Electrochemistry HOTs Class 12 Chemistry

Nandini, a young scientist, tried different electrolysis experiments using various electrolytes.
The incorrect observation of her experiment is
(a) cations which get reduced at cathode preferentially are hydronium ions in electrolysis of aqueous NaCl
(b) cations reaching to cathode are Cu2+ ions during electrolysis of CuSO4 solution
(c) during electrolysis of conc. H2SO4, S2O82– is formed at anode
(d) S2O82– is formed at anode during electrolysis of CuSO4 solution. 

Answer

D

Question. Molar conductivity of NH4OH can be calculated by the equation,

Electrochemistry HOTs Class 12 Chemistry
Answer

C

Question. Two solutions of X and Y electrolytes are taken in two beakers and diluted by adding 500 mL of water. Lm of X increases by 1.5 times while that of Y increases by 20 times, what could be the electrolytes X and Y ?
(a) X → NaCl, Y → KCl
(b) X → NaCl, Y → CH3COOH
(c) X → KOH, Y → NaOH
(d) X → CH3COOH, Y → NaCl

Answer

B

Question. Shubh learnt during his electrochemistry class that the standard electrode potentials are very important and we can extract a lot of useful informations from them. If the standard electrode potential of an electrode is greater than zero then its reduced form is more stable compared to hydrogen gas. Similarly, if the standard electrode potential is negative then hydrogen gas is more stable than the reduced form of the species.
Based on the given data,

Electrochemistry HOTs Class 12 Chemistry

He made following conclusions:
I. SnSO4 solution can be stored in Fe vessel.
II. FeSO4 solution can be stored in Zn vessel.
III. Cr2(SO4)3 solution can be stored in Sn vessel.
IV. ZnSO4 solution cannot be stored in iron vessel.
The correct conclusion(s) is/are
(a) I and II
(b) III and IV
(c) III only
(d) all of these. 

Answer

C

Question. Mark the incorrect statement.
(a) The limiting equivalent conductance for weak electrolytes can be computed with the help of Kohlrausch’s law.
(b) EMF of a cell is the difference in the reduction potentials of cathode and anode.
(c) For cell reaction to occur spontaneously, the EMF of the cell should be negative.
(d) Fluorine is the strongest oxidising agent as its reducing potential is very high.

Answer

C

Question. When a lead storage battery is discharged:
(a) SO2 is evolved
(b) lead is formed
(c) H2SO4 is consumed
(d) PbSO4 is consumed

Answer

C

Question. How many coulomb are required for the oxidation of 1 mol of H2O2 to O2?
(a) 9.65 × 104 C
(b) 93000 C
(c) 1.93 × 105C
(d) 19.3 × 102C

Answer

C

Question.KCl is used in salt bridge because:
(a) It forms a good jelly with agar-agar
(b) It is a strong electrolyte
(c) It is a good conductor of electricity
(d) Migration factor of K+ and Cl– ions are almost equal

Answer

D

Question. The nature of curve of E° cell against log KC is:
(a) a straight line
(b) parabola
(c) a hyperbola
(d) an elliptical curve

Answer

A

Question. For a spontaneous reaction the ΔG, equilibrium constant (K) and E°cell will be respectively.
(a) – ve, < 1, – ve
(b) – ve, > 1, – ve
(c) – ve, > 1, + ve
(d) + ve, > 1, – ve

Answer

C

Question. Determine the value of E°cell for the following reaction, cu2+ + Sn+2 → Cu + Sn+4, equilibrium constant is 106.
(a) 0.1773
(b) .01773
(c) 0.2153
(d) 1.773

Answer

A

Question. Which is the best reducing agent?
(a) F
(b) Cl
(c) Br
(d) I

Answer

D

Question.If a salt bridge is removed between the half cells, the voltage:
(a) drops to zero
(b) does not change
(c) increase gradually
(d) increases rapidly

Answer

A

Question. Faraday’s law of electrolysis are related to the:
(a) Atomic number of the cation
(b) atomic number of the anion
(c) equivalent weight of the electrolyte
(d) speed of the cation

Answer

C

Question. The process in which chemical change occurs on passing electricity is termed:
(a) Ionisation
(b) neutralisation
(c) electrolysis
(d) hydrolysis

Answer

C

Question. The charge required for the reduction of 1 mol of MnO4 to MnO2 is:
(a) 1 F
(b) 3 F
(c) 5 F
(d) 4 F

Answer

B

Question. The value of Λºm for NH4Cl, NaOH and NaCl are 129.8, 248.1 and 126.4 Ohm–1 cm2 mol–1 respectively. Calculate Λºm for NH4OH solution.
(a) 215.5
(b) 251.5
(c) 244.7
(d) 351.5

Answer

B

Question. A current of 9.65 amp flowing for 10 minutes deposits 3.0 g of a metal. The equivalent wt. of the metal is:
(a) 10 g
(b) 30 g
(c) 50 g
(d) 96.5 g

Answer

C

Question. In a Golvenic cell the electrical work done is equal to:
(a) free energy change
(b) mechanical work done
(c) thermodynamic work done
(d) all of the above

Answer

A

Question. When lead storage battery is charged it is:
(a) an electrolyte cell
(b) a galvenic cell
(c) a daniel cell
(d) a and b both

Answer

A

Question. In a galvenic cell the direction of current is:
(a) anode to cathode
(b) cathode to anode
(c) Zn rod to Cu rod
(d) Depend on concentration of ZnSO4 and CuSO4

Answer

B

Question. Which metal does not give the following reaction M + water → oxide or hydroxide + H2
(a) Fe
(b) Na
(c) Hg
(d) Ag

Answer

C,D

Question. Electrolysis of aq. CuSO4 produces:
(a) an increase in pH
(b) a decrease in pH
(c) either decrease or increase
(d) H2SO4 in the solution

Answer

B,D

Question. Zn cannot displace following ions from their aquous solution:
(a) Al+3
(b) Cu2+
(c) Fe2+
(d) Na+

Answer

A,D

Question. Which one is not a secondary battery?
(a) laclanche cell
(b) Ni-Cd cell
(c) Mercury cell
(d) Daniel cell

Answer

A,C,D

Question. Which of the following decrease with increase in concentration?
(a) conductance
(b) specifci conductance
(c) Molar conductance
(d) Conductivity

Answer

A,C

Fill in the blanks type question:

Question. To deposite 2 mol of Ca from CaCl2 …………… electricity is required. 

Answer

4 F

Question. ……………… gives a constant voltage throughout its life. 

Answer

Mercury cell

Question. Match the column and choose correct option:
(A) Conductance               P. m–1
(B) Conductivity               Q. 5 cm–1
(C) Molar conductance      R. Siemen
(D) Cell constant              S. 5 cm2 mol–1
(a) A–R, B–Q, C–S, D–P
(b) A–R, B–S, C–Q, D–P
(c) A–R, B–Q, C–P, D–S
(d) A–R, B–P, C–Q, D–S

Answer

A

Question. Match the column and choose correct option:
(A) MnO4 → Mn+2 (1 mol)       P. Required 1F
(B) CuSO4 → Cu (1 mol)                Q. Required 5 F
(C) Al2O3 → Al (1 mol)                   R. Required 3 F
(D) NaCl → Na (1 mol)                   S. Required 2 F
(a) A–Q, B–P, C–S, D–R
(b) A–P, B–Q, C–S, D–R
(c) A–Q, B–S, C–P, D–R
(d) A–Q, B–S, C–R, D–P

Answer

D