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3.ELECTROCHEMISTRY (1.)The EM3+/M2+ ° values for Cr, Mn, Fe and Co are - 0.41 V, +1.57 V, +0.77 V and +1.97 V respectively. For which one of these metals the change in oxidation state from +2 to +3 is easiest? (a.) Cr (b.) Mn (c.) Fe (d.) Co (2.)Reduction potential of four elements P,Q, R, S is −2.90, +0.34, +1.20 and −0.76. Reactivity decreases in the order (a.) P > Q > R > S (b.) S > R > Q > P (c.) P > S > Q > R (d.) Q > S > R > P (3.)The emf of the cell, Ag | Ag+ (0.1 M) || Ag+ (1 M) | Ag at 298 K is (a.) 0.0059 V (b.) 0.059 V (c.) 5.9 V (d.) 0.59 V (4.)Use of electrolysis is (a.) Electrorefining (b.) Electroplating (c.) Both (a) and (b) (d.) None of these (5.)Corrosion of iron is essentially an electrochemical phenomenon where the cell reactions are (a.) Fe is oxidised to Fe2+ and dissolved oxugen in water is reduced to OH− (b.) Fe is oxidised to Fe3+ and H2O is reduced to O2 2− (c.) Fe is oxidised to Fe2+ and H2O is reduced to O2 − (d.) Fe is oxidised to Fe2+ and H2O is reduced to O2 (6.)When X amperes of current is passed through molten AlCl3 for 96.5 s. 0.09 g of aluminium is deposited. What is the value of X? (a.) 10 A (b.) 20 A (c.) 30 A (d.) 40 A (7.)The amount of electricity required to liberate 1 g-equiv of Cu is (a.) 96500 F (b.) 1 F (c.) 1 C (d.) 96500 A (8.)The standard reduction potential, E° for the half- reactions are as Zn ⇌ Zn2+ + 2e −,E° =⊕ 0.76 V Fe ⇌ Fe2+ + 2e −,E° = +0.41 V The E°cell for the cell formed by these two electrodes is (a.) −0.35 V (b. ) − 1.17 V (c.) +0.35 V (d.) +1.17 V (9.)EFe3+/Fe ° = −0.036 V , EFe2+/Fe ° = −0.439 V. The value of standard electrode potential for the charge, Fe 3+ (aq) + e − ⟶ Fe 2+ (aq) will be (a.) -0.072 V (b.) 0.385 V (c.) 0.770 V (d.) -0.270 V (10.)The hydrogen electrode is dipped in Asolution of pH 3 at 25°C. The potential would be (the value of 2.303 RT /F is 0.059 V) (a.) 0.177 V (b.) 0.087 V (c.) 0.059 V (d.) -0.177 V (11.)An electrochemical cell is set up as follows Pt(H2, 1 atm) | 0.1 M HCl | |0.1 M acetic acid | (H2, 1 atm)Pt Emf of this cell will not be zero because (a.) The pH of 0.1 M HCl and 0.1 M acetic acid is not the same (b.) Acids used in two compartments are different (c.) Emf of a cell depends on the molarities of acids used (d.) The temperature is constant (12.)Zn2+ ⟶ Zn (s); E ° = −0.76 V Cu2+ ⟶ Cu (s); E ° = −0.34 V Which of the following is spontaneous? (a.) Zn2+ + Cu ⟶ Zn + Cu2+ (b. ) Cu2+ + Zn ⟶ Cu + Zn2+ (c.) Zn2+ + Cu2+ ⟶ Zn + Cu (d. ) None of the above (13.)What will be the emf for the given cell Pt | H2 (p1 ) |H +(aq)|| H2 (p2 ) | Pt? (a.) RT 2F log p1 p2 (b.) RT F log p1 p2 (c.) RT F log p2 p1 (d.) None of these
(14.)By diluting a weak electrolyte , specific conductivity (Kc) and equivalent conductivity (λc) change as (a.) Both increase (b.) Kc increases , λc decreases (c.) Kc decreases , λc increases (d.) Both decrease (15.)Electrolytes, when dissolved in water, dissociate into their constituent ions. The degree of dissociation of a weak electrolyte increases with (a.) The presence of a substance yielding common ion (b.) Decreasing temperature (c.) Decreasing concentration of the electrolyte (d.) Increasing concentration of the electrolyte (16.)By passing 9.65 A current for 16 min 40 s , the volume of O2 liberated at STP will be (a.) 280 mL (b.) 560 mL (c.) 1120 mL (d.) 2240 mL (17.)What is the cell reaction occurring in Daniel cell (Galvanic cell)? (a.) Cu(s) + ZnSO4 (aq) ⟶ CuSO4 (aq) + Zn(s) (b. ) Zn(s) + CuSO4 (aq) → Cu(s) + ZnSO4 (aq) (c.) Ni(s) + ZnSO4 (aq) ⟶ NiSO4 (aq) + Zn(s) (d. ) 2Na(s) + CdSO4 (aq) ⟶ Na2SO4 (aq) + Cd (s) (18.)Conductivity of a strong electrolyte (a.) Decreases on dilution (b.) Increases on dilution (c.) Does not change considerably on dilution (d.) Depends on density (19.)Give the products available on the cathode and the anode respectively during the electrolysis of an aqueous solution of MgSO4 between inert electrodes. (a.) H2 (g) and O2(g) (b.) O2 (g) and H2(g) (c.) O2 (g) and Mg(s) (d.) O2 (g) and SO2(g) (20.)A solution containing one mole per litre of each Cu(NO3 )2, AgNO3,Hg2 (NO3 )2 and Mg(NO3 )2 is being electrolysed by using inert electrodes. The values of standard electrode potentials in volts (reducing potentials) are Ag/Ag+ = +0.80, 2Hg/ Hg2+ = +0.79, Cu/Cu2+ = +0.34, Mg/Mg2+ = −2 With increasing voltage, the sequence of deposition of metals on the cathode will be (a.) Ag, Hg, Cu (b.) Cu,Hg, Ag (c.) Ag,Hg, Cu, Mg (d.) Mg, Cu,Hg, Ag (21.)In Agalvanic cell, the electrons flow from (a.) Anode to cathode through the solution (b.) Cathode to anode through the solution (c.) Anode to cathode through the external circuit (d.) Cathode to anode through the external circuit (22.)By how much is the oxidizing power of Cr2O7 2−/Cr3+ couple decreased if the H + concentration is decreased from 1 M to 10−3 M at 25°C? (a.) 0.207 V (b.) 0.414 V (c.) 0.001 V (d.) 0.287 V (23.)What is the value of Ecell? Cr | Cr3+ (0.1 M) || Fe2+ (0.01 M) | Fe Given, E°Cr3+/Cr = −0.74 V and E°Fe2+/Fe = −0.44 V (a.) +0.2941 V (b.) +0.5212 V (c.) +0.1308 V (d.) -0.2606 V (24.)The reduction electrode potential, E of 0.1 M solution of M+ ions (ERP = −2.36 V) is (a.) -4.82 V (b.) -2.41 V (c.) +2.41 V (d.) None of these (25.)The resistance of N 10 solution is found to be 2.5 × 103Ω . The equivalent conductance of the solution is (cell constant = 1.25cm−1 ) (a.) 2.5Ω−1 cm2 equiv−1 (b.) 5.0Ω−1 cm2 equiv−1 (c.) 2.5Ω−1 cm−2 equiv−1 (d.) 5.0Ω−1 cm−2 equiv−1 (26.)The cell reaction is spontaneous, when (a.) Ered ° is negative (b.) Ered ° is positive (c.) ΔG ° is negative (d.) ΔG ° is positive (27.)Using the following data, for the electrode potentials calculate ∆G°, in kJ, for the indicated reaction 5Ce4+(aq) + Mn2+(aq) + 4H2O(l) → 5Ce3+(aq) + MNO4 −(aq) + 8H +(aq) MnO4 −(aq) + 8H +(aq) + 5e − → Mn2+(aq) + 4H2O(l) E° = +1.51 V Ce4+(aq) + e − → Ce3+(aq) E° = +1.61 V (a.) −36.24 (b. ) − 48.25 (c.) −31.54 (d. ) − 19.65
(28.)Resistance of a conductivity cell filled with a solution of an electrolyte of concentration 0.1 M is 100Ω. The conductivity of this solution is 1.29 S m−1 . Resistance of the same cell when filled with 0.2 M of the same solution is 520Ω. The molar conductivity of 0.02 M solution of the electrolyte will be (a.) 124 × 10−4 S m2 mol−1 (b.) 1240 × 10−4 S m2 mol−1 (c.) 1.24 × 10−4 S m2 mol−1 (d.) 12.4 × 10−4 S m2 mol−1 (29.)The units of equivalent conductance, are (a.) Ω cm2 equiv−1 (b.) Ω cm2 equiv (c.) Ω −1 cm2 equiv−1 (d.) Ω cm2 equiv (30.)The specific conductance of 0.1 N KCl solution at 23°C is 0.012 ohm−1 cm−1 . The resistance of cell containing the solution at the same temperature was found to be 55 ohm. The cell constant will be (a.) 0.66 cm−1 (b.) 1.12 cm−1 (c.) 0.918 cm−1 (d.) 1.66 cm−1 (31.)Cu+ (aq) is unstable in solution and undergoes simultaneous oxidation and reduction, according to the reaction 2Cu+ (aq) ⇌ Cu2+ (aq) + Cu (s) choose correct E ° for the above reaction if ECu2+/Cu ° = 0.34 V , ECu2+/Cu+ ° = 0.15 V (a.) -0.38 V (b.) +0.49 V (c.) +0.38 V (d.) -0.19 V (32.)In a galvanic cell, the electrons flow from (a.) Anode to cathode through the external circuit (b.) Anode to cathode through the solution (c.) Cathode to anode through the external circuit (d.) Cathode to anode through the solution (33.)When Cu reacts with AgNO3 solution, the reaction takes place is (a.) Oxidation of Cu (b.) Reduction of Cu (c.) Oxidation of Ag (d.) Reduction of NO3 − (34.)A silver cup is plated with silver by passing 965 C of electricity. The amount of Ag deposited is (a.) 107.89 g (b.) 9.89 g (c.) 1.0002 g (d.) 1.08 g (35.)The value of Λeq ∞ for NH4Cl,NaOH and NaCl are respectively,149.74,248.1 and 126.4Ω −1 cm2 equiv −1 . The value of Λeq ∞ of NH4OH is (a.) 371.44 (b.) 271.44 (c.) 71.44 (d.) Cannot be predicted from given data (36.)The standard electrode potential for the half – cell reactions are Zn2+ + 2e − ⟶ Zn; E ° = -0.76 V Fe2+ + 2e − ⟶ Fe; E ° = -0.44 V The emf of the cell reaction, Fe2+ + Zn ⟶ Zn2+ + Fe is (a.) -0.32 V (b.) -1.20 V (c.) +1.20 V (d.) +0.32 V (37.)The best way to prevent rusting of iron is (a.) Making it cathode (b.) Putting in saline water (c.) Both (a) and (b) (d.) None of these (38.)The equivalent conductivity of a solution containing 2.54 g of CuSO4 per L is 91.0 Ω −1 cm2 eq−1 . Its conductivity would be (a.) 2.9 × 10−3 Ω −1 cm2 (b.) 1.8 × 10−2 Ω −1 cm2 (c.) 2.4 × 10−4 Ω −1 cm2 (d.) 3.6 × 10−3 Ω −1 cm2 (39.)9.65 C electric current is passed through fused anhydrous MgCl2. The magnesium metal thus obtained is completely converted into a Grignard reagent. The number of moles of Grignard reagent obtained is (a.) 5 × 10−4 (b.) 1 × 10−4 (c.) 5 × 10−5 (d.) 1 × 10−5 (40.)In the electrolysis of water, 1 F of electrical energy would evolve (a.) 1 mole of oxygen (b.) 1 g atom of oxygen (c.) 8 g of oxygen (d.) 22.4 L of oxygen (41.)The standard oxidation potentials of Zn, Cu, Ag and Ni electrodes are + 0.76, -0.34, -0.80 and +0.25 V respectively. Which of the following reaction will provide maximum voltage? (a.) Cu + 2 Ag+ (aq) → Cu2+ (aq) + 2 Ag (b. ) Zn + 2 Ag+ (aq) → Zn2+ (aq) + 2 Ag (c.) H2 + Ni2+ (aq) → 2H+ (aq) + Ni (d. ) Zn + Cu2+ (aq) → Zn2+ (aq) + Cu (42.)The E °of Fe2+ / Fe and Sn2+ /Sn are -0.44 V and -0.14 V respectively. If cell reaction is
Fe + Sn2+ → Fe2+ + Sn then emf of the cell is (a.) +0.30 V (b.) -0.58 V (c.) +0.58 V (d.) -0.30 V (43.)How long (in hours) must a current of 5.0 A be maintained to electroplate 60 g of calcium from molten CaCl2? (a.) 27 h (b.) 8.3 h (c.) 11 h (d.) 16 h (44.)In Acell that utilises the reaction, Zn (s) + 2H+ (aq) → Zn2+(aq) + H2 (g) addition of H2SO4 to cathode compartment, will (a.) Lower the E and shift the equilibrium to the left (b.) Lower the E and shift the equilibrium to the right (c.) Increase the E and shift the equilibrium to the right (d.) Increase the E and shift the equilibrium to the left (45.)Molar conductance of electrolytic solution Λm is (a.) ∝ l (b.) ∝ (1/A) (c.) ∝ (1/C) (d.) ∝ (√C) (46.)Reduction potentials of A, B, C, and D are 0.8 V, 0.79 V, 0.34 V and -2.37 V respectively. Which element displaces all the other three elements? (a.) B (b.) A (c.) D (d.) C (47.)Standard electrode potential of cell H2 |H +||Ag+|Ag is (Given,E°Ag+/Ag = 0.80 V) (a.) 0.4 V (b.) 0.8 V (c.) 1.4 V (d.) 1.8 V (48.)Which of the following reactions is used to make a fuel cell? (a.) 2H2 (g) + O2 (g) → 2H2O(l) (b.) 2Fe(s) + O2 (g) + 4H +(aq) → 2Fe2+(aq) + 2H2O(l) (c.) Pb(s) + PbO2 (s) + 2H2SO4 (aq) → 2PbSO4 (s) + H2O(l) (d.) Cd(s) + 2Ni(OH)3 (s) → CdO(s) + 2Ni(OH)2 + 2H2O(l) (49.)Two different electrolytic cells filled with molten Cu(NO3)2 and molten Al(NO3)3 respectively are connected in series. When electricity is passed 2.7 g Al is deposited on electrode. Calculate the weight of Cu deposited on cathode. [Cu = 63.5;Al = 27.0 g mol−1 ] (a.) 190.5 g (b.) 9.525 g (c.) 63.5 g (d.) 31.75 g (50.)Specific conductivity of a solution (a.) Increases with dilition (b.) Decreases with dilution (c.) Remains unchanged with dilution (d.) Depends on mass of electrolyte (51.)The ionic conductance of Ba2+ and Cl− are respectively 127 and 76 Ω −1 cm2 at infinite dilution. The equivalent conductance (in Ω −1 cm2 ) of BaCl2 at infinite dilution will be (a.) 139.5 (b.) 203 (c.) 279 (d.) 101.5 (52.)The standard reduction potential E ° for the half reactions are as Zn → Zn2+ + 2e − , E ° = 0.76 V Cu → Cu2+ + 2e − , E ° = 0.34 V The emf for the cell reaction, Zn + Cu2+ → Zn2+ + Cu (a.) 0.42 V (b.) -0.42 V (c.) -1.1 V (d.) 1.1 V (53.)If ‘F’ is faraday and ‘N’ is Avogadro number, then charge of electron can be expressed as (a.) F × N (b.) F N (c.) N F (d.) F 2N (54.)The cell reaction of Acell is Mg (s) + Cu2+ (aq) ⟶ Cu (s) + Mg2+ (aq) . If the standard reduction potentials of Mg and Cu are – 2.37 and + 0.34 V respectively. The emf of the cell is (a.) 2.03 V (b.) -2.03 V (c.) +2.71 V (d.) -2.71 V (55.)Daniel cell, anode and cathode are respectively (a.) Zn | Zn2+ and Cu2+ | Cu (b. ) Cu | Cu2+ and Zn2+ | Zn (c.) Fe | Fe2+ and Cu2+ | Cu (d. ) Cu | Cu2+ and Fe2+ | Fe (56.)Astandard hydrogen electrode has zero electrode potential because (a.) Hydrogen is easier to oxidise