Electrochemistry PYQs Set 11 (PDF)

Set 11 of 13 · Questions 301-330 of 363

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JEE Main Chemistry · Electrochemistry · Set 11 (Q301-330)

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301.
The standard electrode potential $E^{0}$ and its temperature coefficient $(\frac{dE ^{0}}{dT})$ for a cell are $2 V$ and $- 5 \times 10^{- 4} VK^{- 1}$ at $300$ K respectively. The cell reaction is:
$Zn (s) + Cu^{2 +} (aq) \to Zn^{2 +} (aq) + Cu$
The standard reaction enthalpy $(Δ_{r} H^{0})$ at $300 K$ in $kJ mol^{- 1}$ is, $(Use R = 8 JK^{- 1} mol^{- 1} and F = 96, 000 C mol^{- 1})$
1. (1) $- 412.8$
2. (2) $- 384.0$
3. (3) $192.0$
4. (4) $206.4$
302.
The electrolyte used in mercury cell iS
1. (1) $Moist paste of NH_{4} Cl and ZnCl_{2}$
2. (2) $38% solution of H_{2} SO_{4}$
3. (3) $Paste of KOH and ZnO$
4. (4) $Paste of MgCl_{2} and HgO$
303.
In the given electrochemical cell, $Ag (s) | AgCl (s) | FeCl_{2} (aq), FeCl_{3} (aq) ∣ Pt (s)$ at 298 K , the cell potential $(E_{cell})$ will increase when :(A) Concentration of Fe2+ is increased.(B) Concentration of Fe3+ is decreased.(C) Concentration of Fe2+ is decreased.(D) Concentration of Fe3+ is increased.(E) Concentration of $Cl^{-}$ is increased.
Choose the correct answer from the options given below:
1. (1) $(B) Only$
2. (2) $(A) and (E) Only$
3. (3) $(C) (D) and (E) Only$
4. (4) $A and B Only$
304.
Given below are two statements:
Statement I: Mohr's salt is composed of only three types of ions-ferrous, ammonium and sulfate.
Statement II: If the molar conductance at infinite dilution for ferrous, ammonium and sulfate ions are $x_{1}, x_{2}$ and $x_{3} S cm^{2} mol^{- 1}$ , respectively then the molar conductance for Mohr's salt solution at infinite dilution would be given by $x_{1} + x_{2} + 2 x_{3}$
In the light of the given statements, choose the correct answer from the options given below:
1. (1) $Both Statements I and Statement II are true$
2. (2) $Statement I is true but Statement II is false$
3. (3) $Both Statements I and Statement II are false$
4. (4) $Statement I is false but Statement II is true$
305.
Given below are two statements:
1 M aqueous solutions of each of $Cu (NO_{3})_{2}$ , $AgNO_{3}, Hg_{2} (NO_{3})_{2}, Mg (NO_{3})_{2}$ are electrolysed using inert electrodes. Given: $E^{0}$ Ag+/Ag $= 0.80 V$ , $E^{0}_{Hg_{2}^{2 +} / Hg}$ $0.79 V, E^{0}_{Cu^{2 +} / Cu} = 0.24 V$ and $E^{0}_{Mg^{2 +} / Mg} = - 2.37 V$ .
Statement (I): With increasing voltage, the sequence of deposition of metals on the cathode will be $Ag, Hg$ and Cu.
Statement (II): Magnesium will not be deposited at the cathode instead oxygen gas will be evolved at the cathode.
In the light of the above statements, choose the most appropriate answer from the options given below:
1. (1) $Both Statement I and Statement II are incorrect$
2. (2) $Statement I is incorrect but Statement II is correct$
3. (3) $Statement I is correct but Statement II is incorrect$
4. (4) $Both Statement I and Statement II are correct$
306.
$E_{1}, E_{2}$ and $E_{3}$ are the emfs of the following three galvanic cells respectively.
(i) $Zn_{(s)} (Zn^{2 +} (0.1 M)) (Cu^{2 +} (1 M)) Cu_{(s)}$
(ii) $Zn_{(s)} (Zn^{2 +} (1 M)) (Cu^{2 +} (1 M)) Cu_{(s)}$
(iii) $Zn_{(s)} (Zn^{2 +} (1 M) ∥ Cu^{2 +} (0.1 M)) Cu_{(s)}$
Which one of the following is true?
1. (1) $E_{2} > E_{1} > E_{3}$
2. (2) $E_{1} > E_{2} > E_{3}$
3. (3) $E_{3} > E_{1} > E_{2}$
4. (4) $E_{3} > E_{2} > E_{1}$
307.
Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox titration. Some half cell reactions and their standard potentials are given below :
MnO $_{4}^{-}$ (aq.) + $8 H^{+}$ (aq.) + $5 e^{-}$ → $M n^{2 +}$ (aq.) + $4 H_{2}$ O(λ) Eº = 1.51 V
$C r_{2}$ O $_{7}^{2-}$ (aq.) + $14 H^{+}$ (aq.) + $6 e^{-}$ → $2 C r^{3 +}$ (aq.) + $7 H_{2}$ O(λ) Eº = 1.38 V
$F e^{3 +}$ (aq.) + $e^{-}$ → $F e^{2 +}$ (aq.) Eº = 0.77 V
$C l_{2}$ (g) + $2 e^{-}$ → $2 C l^{-}$ (aq.) Eº = 1.40 V
Identify the only incorrect statement regarding the quantitative estimation of aqueous Fe $(N O_{3})_{2}$ :
1. (1) $MnO_{4}^{-} can be used in aqueous HCl.$
2. (2) $C r_{2} O_{7}^{2-} can be used in aqueous HCl.$
3. (3) $MnO_{4}^{-} can be used in aqueous H_{2} S O_{4}$
4. (4) $C r_{2} O_{7}^{2-} can be used in aqueous H_{2} S O_{4}$
308.
The unit of conductivity is
1. (1) $S / m$
2. (2) $S / m^{2}$
3. (3) $Sm$
4. (4) $none of these.$
309.
In the cell $Pt (s) (H_{2} (g, 1 bar) / HCl (aq) ∥ AgCl (s) / Ag (s)) Pt (s)$ the cell potential is $0.92 V$ when a $10^{- 6}$ molal $HCl$ solution is used. The standard electrode potential of $(AgCl / Ag, Cl^{-})$ electrode is:
$(Given : \frac{2.303 RT}{F} = 0.06 V at 298 K)$
1. (1) $0.94 V$
2. (2) $0.76 V$
3. (3) $0.40 V$
4. (4) $0.20 V$
310.
The electrode potentials for $C u_{(a q)}^{2 +} + e^{-} \to C u_{(a q)}^{+}$ and $C u_{(a q)}^{+} + e^{-} \to C u_{(s)}$ are $+ 0.15 V$ and $+ 0.50 V$ respectively. The value of $E_{C u^{2 +} / C u}^{\circ}$ will be
1. (1) $0.500 V$
2. (2) $0.325 V$
3. (3) $0.650 V$
4. (4) $0.150 V$
311.
Galvanization is applying a coating of :
1. (1) $Cr$
2. (2) $Cu$
3. (3) $Zn$
4. (4) $Pb$
312.
Which from following is not true about voltaic cell?
1. (1) $The anode acts as negative electrode.$
2. (2) $The cathode acts as a positive electrode.$
3. (3) $It converts electrical energy into chemical energy.$
4. (4) $Dry cell is an example of voltaic cell$
313.
Which of the following statements is not correct about rusting of iron?
1. (1) $Coating of iron surface by tin prevents rusting, even if the tin coating is peeling off.$
2. (2) $When pH lies above 9 or 10 , rusting of iron does not take place.$
3. (3) $Dissolved acidic oxides SO_{2}, NO_{2} in water act as catalyst in the process of rusting.$
4. (4) $Rusting of iron is envisaged as setting up of electrochemical cell on the surface of iron object.$
314.
Fuel cell, using hydrogen and oxygen as fuels,
A. has been used in spaceship
B. has as efficiency of $40 %$ to produce electricity
C. uses aluminum as catalysts
D. is eco-friendry
E. is actually a type of Galvanic cell only
Choose the correct answer from the options given below:
1. (1) $A, B, D, E only$
2. (2) $A, D, E only$
3. (3) $A, B, D only$
4. (4) $A, B, C only$
315.
A variable, opposite external potential $(E_{e x t}$ ) is applied to the cell Zn| $Zn^{2 +}$ (1 M) || $Cu^{2 +}$ (1M) | Cu, of potential 1.1 V. When Eext < 1.1 V and Eext > 1.1 V respectively electrons flow from:
1. (1) $Cathode to anode in both cases$
2. (2) $cathode to anode and anode to cathode$
3. (3) $anode to cathode and cathode to anode$
4. (4) $anode to cathode in both cases$
316.
For the given cell $Fe^{2 +}_{(aq)} + Ag^{+}_{(aq)} \to Fe_{(aq)}^{3 +} + Ag_{(s)}$ The standard cell potential of the
above reaction is
$Ag^{+} + e^{-} \to Ag E^{θ} = xV$
Given: $Fe^{2 +} + 2 e^{-} \to Fe E^{θ} = yV$
$Fe^{3 +} + 3 e^{-} \to Fe E^{θ} = zV$
1. (1) $x + y - z$
2. (2) $x + 2 y$
3. (3) $x + 2 y - 3 z$
4. (4) $y - 2 x$
317.
Which of the following is incorrect in a galvanic cell?
1. (1) $Oxidation occurs at anode.$
2. (2) $Reduction occurs at cathode.$
3. (3) $The electrode at which electrons are gained is called cathode.$
4. (4) $The electrode at which electrons are lost is called cathode.$
318.
$The standard reduction potentials at 298 K for the following half cells are given below : Cr_{2} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 Cr^{3 +} + 7 H_{2} O, E^{\circ} = 1.33 V Fe^{3 +} (aq) + 3 e^{-} \to Fe E^{\circ} = - 0.04 V Ni^{2 +} (aq) + 2 e^{-} \to Ni E^{\circ} = - 0.25 V Ag^{+} (aq) + e^{-} \to Ag E^{\circ} = 0.80 V Au^{3 +} (aq) + 3 e^{-} \to Au E^{\circ} = 1.40 V Consider the given electrochemical reactions, The number of metal(s) which will be oxidized be Cr_{2} O_{7}^{2 -}, in aqueous solution is_____$
319.
$The photoelectric current from Na (work function, w_{0} = 2.3 eV) is stopped by the output voltage of the cell Pt (s) (H_{2} (g, 1 bar)) HCl (aq . pH = 1) (AgCl (s)) Ag (s) The pH of aq. HCl required to stop the photoelectric current from K (w_{0} = 2.25 eV), all other conditions remaining the same, is \times 10^{- 2} (to the nearest integer). Given: 2.303 \frac{RT}{F} = 0.06 V; E_{AgClAglCC^{-}}^{= 0} = 0.22 V$
320.
$Consider the following half cell reaction Cr_{2} O_{7}^{2 -} (aq) + 6 e^{-} + 14 H^{+} (aq) \to 2 Cr^{3 +} (aq) + 7 H_{2} O (l) The reaction was conducted with the ratio of \frac{( Cr ^{3 +} ) ^{2}}{( Cr _{2} O _{7}^{2 -} )} = 10^{- 6} . The pH value at which the EMF of the half cell will become zero is .(nearest integer value) [Given: standard half cell reduction potential E_{Cr_{2} O_{7}^{2 -}, H^{+} / Cr^{3 +}}^{\circ} = 1.33 V, \frac{2.303 RT}{F} = 0.059 V .]$
321.
$The pH and conductance of a weak acid (HX) was found to be 5 and 4 \times 10^{- 5} S, respectively. The conductance was measured under standard condition using a cell where the electrode plates having a surface area of 1 cm^{2} were at a distance of 15 cm apart. The value of the limiting molar conductivity is____Sm^{2} mol^{- 1} . (nearest integer) (Given : degree of dissociation of the weak acid (α) ≪ 1)$
322.
$Consider the following redox reaction taking place in acidic medium BH_{4}^{-} (aq) + ClO_{3}^{-} (aq) ⟶ H_{2} BO_{3}^{-} (aq) + Cl^{-} (aq) If the Nernst equation for the above balanced reaction is E_{cell} = E_{cell}^{\circ} - \frac{RT}{nF} ln Q, then the value of n is____.(Nearest integer)$
323.
$Copper reduces N O_{3}^{- into} NO and N O_{2} depending upon the concentration of NH O_{3} in solution. (Assuming fixed (C u^{2 +}) and P_{NO} = P_{N O_{2}}) the HN O_{3} concentration at which the thermodynamic tendencyfor reduction of N O_{3}^{-} into NO and N O_{2} by copper is same is 10^{x} M. The value of 2 x is ____ (Rounded-off tothe nearest integer) [Given: E_{C u^{2 +} / Cu}^{0} = 0.34 V, E_{N O_{3}^{-} / NO}^{0} = 0.96 V, E_{N O_{3}^{-} / NO_{2}}^{0} = 0.79 V andat 298K, \frac{RT}{F} (2.303) = 0.059]$
324.
$MX is a sparingly soluble salt that follows the given solubility equilibrium at 298 K . MX (s) ⇌ M^{+} (aq) + X^{-} (aq); K_{sp} = 10^{- 10} If the standard reduction potential for M^{+} (aq) \to + e^{-} M (s) is (E_{M^{+} / M}^{⊖}) = 0.79 V, then the value of the standard reduction potential for the metal/metal insoluble salt electrode E_{X^{-} / MX (s) / M}^{⊖} is____mV. (nearest integer) [Given : \frac{2.303 RT}{F} = 0.059 V]$
325.
$Electricity is passed through an acidic solution of Cu^{2 +} till all the Cu^{2 +} was exhausted, leading to the deposition of 300 mg of Cu metal. However, a current of 600 mA was continued to pass through the same solution for another 28 minutes by keeping the total volume of the solution fixed at 200 mL. The total volume of oxygen evolved at STP during the entire process is____mL. (Nearest integer) [Given: Cu^{2 +} (aq) + 2 e^{-} \to Cu (s) E_{red}^{o} = + 0.34 V O_{2} (g) + 4 H^{+} + 4 e^{-} \to 2 H_{2} OE_{red}^{o} = + 1.23 V Molar mass of Cu = 63.54 g mol^{- 1} Molar mass of O_{2} = 32 g mol^{- 1} Faraday Constant = 96500 Cmol^{- 1} Molar volume at STP = 22.4 L]$
326.
$For strong electrolyte Λ_{m} increases slowly with dilution and can be represented by the equation Λ_{m} = Λ_{m}^{\circ} - Ac^{1/2} Molar conductivity values of the solutions of strong electrolyte AB at 18^{\circ} C are given below:$
$c (mol L^{- 1})$ $0.04$ $0.09$ $0.16$ $0.25$
$Λ_{m} (S cm^{2} mol^{- 1})$ $96.1$ $95.7$ $95.3$ $94.9$
$The value of constant A based on the above data (in) (Scm^{2} mol^{- 1} / (mol / L)^{1/2}) unit is____.$
327.
$Molar conductivity of a weak acid HQ of concentration 0.18 M was found to be 1/30 of the molar conductivity of another weak acid HZ with concentration of 0.02 M. If λ^{\circ} Q^{-} happened to be equal with λ^{\circ} Z^{-}, then the difference of the pK_{a} values of the two weak acids (pK_{a} (HQ) - pK_{a} (HZ)) is____(Nearest integer). [Given: degree of dissociation (α) ≪ 1 for both weak acids, λ^{\circ} : limiting molar conductivity of ions]$
328.
$Consider the following redox reaction : MnO_{4}^{-} + H^{+} + H_{2} C_{2} O_{4} ⇌ Mn^{2 +} + H_{2} O + CO_{2} The standard reduction potentials are given as below (E_{red}^{\circ}) E_{MnO_{4}^{-} / Mn^{2 +}}^{\circ} = + 1.51 V E_{CO_{2} / H_{2} C_{2} O_{4}}^{\circ} = - 0.49 V If the equilibrium constant of the above reaction is given as K_{eq} = 10^{x}, then the value of x =________(nearest integer)$
329.
$The cell potential for Zn∣Z n^{2 +} (aq) ∣∣S n^{x +} ∣Sn is 0.801 V at 298 K. The reaction quotient for the above reaction is 1 0^{- 2} . The number of electrons involved in the given electrochemical cell reaction is ..... (Given E_{Z n^{2 +} ∣ Z n}^{0} = - 0.763 V, E_{S n^{x +} ∣ S n}^{0} = + 0.008 V and \frac{2.303 R T}{F} = 0.06 V)$
330.
$At 298 K, a 1 litre solution containing 10 mmol of C r_{2} O_{7}^{2 -} and 100 mmol of C r^{3 +} shows a pH of 3.0. Given : C r_{2} O_{7}^{2 -} \to C r^{3 +}; E^{\circ} = 1.330 V and \frac{2.303 R T}{F} = 0.059 V The potential for the half cell reaction is x \times 1 0^{- 3} V. The value of x is$