Chapter 9

In the reaction \(4 \mathrm{Fe}+3 \mathrm{O}_{2} \longrightarrow 4 \mathrm{Fe}^{3+}+6 \mathrm{O}_{2}^{2}\) which of the following statements is incorrect? (a) metallic iron is reducing agent (b) \(\mathrm{Fe}^{3+}\) is an oxidizing agent (c) metallic iron is reduced to \(\mathrm{Fe}^{3+}\) (d) redox reaction

A compound contains atoms \(X, Y, Z\) the oxidation number of \(\mathrm{X}\) is \(+2, \mathrm{Y}\) is \(+5\) and \(\mathrm{Z}\) is \(-2\) The possible form of the compound is (a) \(\mathrm{XY}_{1} \mathrm{Z}_{2}\) (b) \(\mathrm{Y}_{2}\left(\mathrm{XZ}_{3}\right)_{2}\) (c) \(\mathrm{X}_{3}\left(\mathrm{YZ}_{4}\right)_{2}\) (d) \(\mathrm{X}_{3}\left(\mathrm{Y}_{4} \mathrm{Z}\right)_{2}\)

Consider the following four electrodes (1) \(\mathrm{Cu}^{2+}(0.0001 \mathrm{M}) \mid \mathrm{Cu}(\mathrm{s})\) (2) \(\mathrm{Cu}^{2+}(0.1 \mathrm{M}) \mid \mathrm{Cu}(\mathrm{s})\) (3) \(\mathrm{Cu}^{2+}(0.01 \mathrm{M}) \mid \mathrm{Cu}(\mathrm{s})\) (4) \(\mathrm{Cu}^{2+}(0.001 \mathrm{M}) \mid \mathrm{Cu}(\mathrm{s})\) If the standard reduction potential of \(\mathrm{Cu}^{2+} \mid \mathrm{Cu}\) is \(+0.34\) \(\mathrm{V}\), the reduction potentials (in volts) of the above electrodes following the order (a) \(\mid>4>3>2\) (b) \(1>2>3>4\) (c) \(3>4>2>1\) (d) \(2>3>4>1\)

In the redox reaction \(\mathrm{xMnO}+\mathrm{yPbO}_{2}+\mathrm{zHNO}_{3} \longrightarrow \mathrm{HMnO}_{4}\) \(+\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{H}_{2} \mathrm{O}\) (a) \(\mathrm{x}=2, \mathrm{y}=5, \mathrm{z}=10\) (b) \(x=10, y=2, z=5\) (c) \(x=3, y=7, z=6\) (d) \(x=5, y=2, z=10\)

If a current of \(80.0\) microampere is drawn from a cell for 100 days, then the number of farads involved are (a) \(7.16 \times 10^{-4}\) (b) \(7.16 \times 10^{-3}\) (c) \(14.32 \times 10^{-3}\) (d) \(3.46 \times 10^{-3}\)

The same amount of electricity was passed through two separate electrolytic cells containing solutions of nickel nitrate and chromium nitrate respectively. If \(0.3\) \(g\) of nickel was deposited in the first cell, the amount of chromium deposited is (atomic weight of \(\mathrm{Ni}=59\), \(\mathrm{Cr}=52)\) (a) \(0.130 \mathrm{~g}\) (b) \(0.236 \mathrm{~g}\) (c) \(0.176 \mathrm{~g}\) (d) \(1.76 \mathrm{~g}\)

The charge required to deposit \(40.5 \mathrm{~g}\) of \(\mathrm{Al}\) (atomic mass \(=27.0 \mathrm{~g}\) ) from the fused \(\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}\) is (a) \(0.434 \times 10^{5} \mathrm{C}\) (b) \(4.34 \times 10^{5} \mathrm{C}\) (c) \(3.34 \times 10^{5} \mathrm{C}\) (d) \(43.4 \times 10^{5} \mathrm{C}\)

A certain current liberates \(0.504 \mathrm{~g}\) of hydrogen in 2 hour. The amount (or mass) of copper deposited at the cathode during the electrolysis of \(\mathrm{CuSO}_{4}\) (aq) solution by the same current flowing for the same time is (atomic masses \(\mathrm{H}=1.0, \mathrm{Cu}=63.5\) ) (a) \(16.0 \mathrm{~g}\) (b) \(32.0 \mathrm{~g}\) (c) \(8.6 \mathrm{~g}\) (d) \(1.60 \mathrm{~g}\)

Which of the following statements are incorrect? (1) specific conductance increases with dilution (2) equivalent conductance decreases with dilution (3) the conductance of all electrolytes increase with temperature Select the correct answer using the codes given below (a) 1 and 2 (b) 1 and 3 (c) 2 and 3 (d) 1,2 and 3

Specific conductance of \(0.01 \mathrm{~N}\) solution of an electrolyte is \(0.00419 \mathrm{mho} \mathrm{cm}^{-1} .\) The equivalent conductance of this solution will be (a) \(4.19 \mathrm{mh} \mathrm{cm}^{2}\) (b) \(419 \mathrm{mho} \mathrm{cm}^{2}\) (c) \(0.0419 \mathrm{mho} \mathrm{cm}^{2}\) (d) \(0.209 \mathrm{mho} \mathrm{cm}^{2}\)

A solution of \(\mathrm{CuSO}_{4}\) is electrolyzed for 7 minutes with a current of \(0.6 \mathrm{~A}\). The amount of electricity passed equal to (a) \(26 \mathrm{C}\) (b) \(4.2 \mathrm{C}\) (c) \(2.6 \times 10^{-4} \mathrm{~F}\) (d) \(2.6 \times 10^{-3} \mathrm{~F}\)

The specific conductance of \(0.1 \mathrm{~N} \mathrm{KCl}\) solution at \(23^{\circ} \mathrm{C}\) is \(0.012 \mathrm{ohm}^{-1} \mathrm{~cm}^{-1}\). The resistance of cell containing the solution at the same temperature was found to be 55 ohm. The cell constant will be (a) \(0.142 \mathrm{~cm}^{-1}\) (b) \(0.616 \mathrm{~cm}^{-1}\) (c) \(6.16 \mathrm{~cm}^{-1}\) (d) \(616 \mathrm{~cm}^{-1}\)

The equivalent conductance of \(\mathrm{Ba}^{2+}\) and \(\mathrm{Cl}^{-}\)are respectively 127 and \(76 \mathrm{ohm}^{-1} \mathrm{~cm}^{2}\) equiv \(^{-1}\) at infinite dilution. The equivalent conductance (in ohm \(^{-1} \mathrm{~cm}^{2}\) equiv-1) of \(\mathrm{BaCl}_{2}\) at infinite dilution will be (a) \(139.5\) (b) 203 (c) 279 (d) \(101.5\)

\(\mathrm{Cu}^{+}(\mathrm{aq})\) is unstable in solution and undergoes simultaneous oxidation and reduction according to the reaction, \(2 \mathrm{Cu}^{+}(\mathrm{aq}) \rightleftharpoons \mathrm{Cu}^{2+}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})\) choose correct \(E^{\circ}\) for above reaction if \(E^{\circ}\left(\mathrm{Cu}^{2+} / \mathrm{Cu}\right)=0.34 \mathrm{~V}\) and \(E^{\circ}\left(\mathrm{Cu}^{2+} / \mathrm{Cu}^{+}\right)=0.15 \mathrm{~V}\) (a) \(-0.38 \mathrm{~V}\) (b) \(+0.49 \mathrm{~V}\) (c) \(+0.38 \mathrm{~V}\) (d) \(-0.19 \mathrm{~V}\)

The standard reduction potentials of \(\mathrm{Ag}, \mathrm{Cu}, \mathrm{Co}\) and \(\mathrm{Zn}\) are \(0.799,0.337,-0.277\) and \(-0.762 \mathrm{~V}\) respectively. Which of the following cells will have maximum cell emf? (a) \(\mathrm{Zn}\left|\mathrm{Zn}^{2+}(\mathrm{IM}) \| \mathrm{Cu}^{2+}(1 \mathrm{M})\right| \mathrm{Cu}\) (b) \(\mathrm{Zn}\left|\mathrm{Zn}^{2+}(\mathrm{lM}) \| \mathrm{Ag}^{+}(\mathrm{IM})\right| \mathrm{Ag}\) (c) \(\mathrm{Cu}\left|\mathrm{Cu}^{2+}(\mathrm{lM}) \| \mathrm{Ag}^{+}(\mathrm{IM})\right| \mathrm{Ag}\) (d) \(\mathrm{Zn}\left|\mathrm{Zn}^{2+}(\mathrm{IM}) \| \mathrm{Co}^{2+}(\mathrm{IM})\right| \mathrm{Co}\)

On the basis of the information available from the reaction, \(\frac{4}{3} \mathrm{Al}+\mathrm{O}_{2} \longrightarrow \frac{2}{3} \mathrm{Al}_{2} \mathrm{O}_{3}\), \(\Delta \mathrm{G}=-827 \mathrm{~kJ} \mathrm{~mol}^{-1}\) of \(\mathrm{O}_{2}\) The minimum emf, required to carry out an electrolysis of \(\mathrm{Al}_{2} \mathrm{O}_{3}\) is \(\left(F=96500 \mathrm{C} \mathrm{mol}^{-1}\right)\) (a) \(6.42 \mathrm{~V}\) (b) \(8.56 \mathrm{~V}\) (c) \(2.14 \mathrm{~V}\) (d) \(4.28 \mathrm{~V}\)

One ampere of current is passed for 9650 seconds through molten \(\mathrm{AlCl}_{3}\). What is the weight in grams of \(\mathrm{Al}\) deposited at cathode? (Atomic weight of \(\mathrm{Al}=27\) ) (a) \(0.9\) (b) \(9.0\) (c) \(0.18\) (d) \(18.0\)

The emf of a Daniell cell at \(298 \mathrm{~K}\) is \(E_{\text {. }}\) \(\mathrm{Zn}\left|\mathrm{ZnSO}_{4} \| \mathrm{CuSO}_{4}\right| \mathrm{Cu}\) \((0.01 \mathrm{M}) \quad(1.0 \mathrm{M})\) when the concentration of \(\mathrm{ZnSO}_{4}\) is \(1.0 \mathrm{M}\) and that of \(\mathrm{CuSO}_{4}\) is \(0.01 \mathrm{M}\), the emf changed to \(E_{2^{\prime}}\) What is the relationship between \(E_{1}\) and \(E_{2}\) ? (a) \(E_{1}=E_{2}\) (b) \(E_{2} \neq E_{1}\) (c) \(E_{1}>E_{2}\) (d) \(E_{1}

The standard emf of a galvanic cell involving cell reaction with \(\mathrm{n}=2\) is found to be \(0.295 \mathrm{~V}\) at \(25^{\circ} \mathrm{C}\). The equilibrium constant of the reaction would be (Given \(\left.F=96500 \mathrm{C} \mathrm{mol}^{-1} ; \mathrm{R}=8.314 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}\right)\) (a) \(2.0 \times 10^{11}\) (b) \(4.0 \times 10^{12}\) (c) \(1.0 \times 10^{2}\) (d) \(1.0 \times 10^{10}\)

If \(E^{\circ}\left(\mathrm{Fe}^{2+} / \mathrm{Fe}\right)=-0.441 \mathrm{~V}\) and \(E^{\circ}\left(\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}\right)=0.771 \mathrm{~V}\), the standard emf of the reaction \(\mathrm{Fe}+2 \mathrm{Fe}^{3+} \longrightarrow 3 \mathrm{Fe}^{2+}\) will be (a) \(1.212 \mathrm{~V}\) (b) \(0.111 \mathrm{~V}\) (c) \(0.330 \mathrm{~V}\) (d) \(1.653 \mathrm{~V}\)

In the redox reaction \(\mathrm{xKMnO}_{4}+\mathrm{yNH}_{3} \longrightarrow \mathrm{KNO}_{3}+\mathrm{MnO}_{2}+\mathrm{KOH}\) \(+\mathrm{H}_{2} \mathrm{O}\) (a) \(x=3, y=8\) (b) \(x=6, y=3\) (c) \(x=5, y=10\) (d) \(x=8, y=3\)

How much chlorine will be liberated on passing one ampere current for 30 min through \(\mathrm{NaCl}\) solution? (a) \(0.66 \mathrm{~mol}\) (b) \(0.33 \mathrm{~mol}\) (c) \(0.66 \mathrm{~g}\) (d) \(0.33 \mathrm{~g}\)

The chemical reaction, \(2 \mathrm{AgCl}(\mathrm{s})+\mathrm{H}_{2}(\mathrm{~g}) \longrightarrow 2 \mathrm{HCl}(\mathrm{aq})+2 \mathrm{Ag}(\mathrm{s})\) taking place in a galvanic cell is represented by the notation (a) \(\mathrm{Pt}(\mathrm{s}) \mid \mathrm{H}_{2}(\mathrm{~g}), 1\) bar \(\mid 1 \mathrm{M} \mathrm{KCl}\) (aq) \(|\mathrm{AgCl}(\mathrm{s})| \mathrm{Ag}\) (s) (b) \(\mathrm{Pt}(\mathrm{s})\left|\mathrm{H}_{2}(\mathrm{~g}), 1 \mathrm{bar}\right| 1 \mathrm{M} \mathrm{KCl}(\mathrm{aq})\left|1 \mathrm{M} \mathrm{Ag}^{+}(\mathrm{aq})\right|\) \(\mathrm{Ag}(\mathrm{s})\) (c) \(\mathrm{Pt}(\mathrm{s}) \mid \mathrm{H}_{2}(\mathrm{~g}), 1\) bar \(\mid 1 \mathrm{M} \mathrm{KCl}\) (aq) \(|\mathrm{AgCl}(\mathrm{s})| \mathrm{Ag}\) (s) (d) \(\mathrm{Pt}(\mathrm{s})\left|\mathrm{H}_{2}(\mathrm{~g}), 1 \mathrm{bar}\right| 1 \mathrm{M} \mathrm{KCl}\) (aq) \(|\mathrm{Ag}(\mathrm{s})| \mathrm{AgCl}\)

One faraday of electricity is passed separately through one litre of one molar aqueous solutions of (i) \(\mathrm{AgNO}_{3}\) (ii) \(\mathrm{SnCl}_{4}\) and (iii) \(\mathrm{CuSO}_{4}\). The number of moles of \(\mathrm{Ag}, \mathrm{Sn}\), and \(\mathrm{Cu}\) deposited at cathode are respectively (a) \(1.0,0.25,0.5\) (b) \(1.0,0.5,0.25\) (c) \(0.5,1.0,0.5\) (d) \(0.25,0.25,0.5\)

\(2 \mathrm{MnO}_{4}+\mathrm{aH}^{+}+\mathrm{bH}_{2} \mathrm{O}_{2} \longrightarrow 2 \mathrm{Mn}^{+2}+\mathrm{H}_{2} \mathrm{O}+\mathrm{dO}_{2}\) What are the values of \(\mathrm{a}, \mathrm{b}, \mathrm{c}\) and \(\mathrm{d} ?\) (a) \(4,5,4,5\) (b) \(6,5,8,5\) (c) \(3,2,4,8\) (d) \(2,5,4,6\)

The electrochemical equivalent of a metal is ' \(\mathrm{x}^{\prime} \mathrm{g}\). coulomb \(^{-1} .\) The equivalent weight of metal is (a) \(\underline{x}\) (b) x. 96500 (c) \(\mathrm{x} / 96500\) (d) \(1.6 \times 10^{-19}\)

In electrolysis of dilute \(\mathrm{H}_{2} \mathrm{SO}_{4}\), what is liberated at anode? (a) \(\mathrm{H}_{2}\) (b) \(\mathrm{SO}_{4}^{2-}\) (c) \(\mathrm{SO}_{2}\) (d) \(\mathrm{O}_{2}\)

In electrolysis of dilute \(\mathrm{H}_{2} \mathrm{SO}_{4}\), what is liberated at anode? (a) \(\mathrm{H}_{2}\) (b) \(\mathrm{SO}_{4}^{2-}\) (c) \(\mathrm{SO}_{2}\) (d) \(\mathrm{O}_{2}\)

Corrosion of iron is essentially an electrochemical phenomenon where the cell reactions are (a) \(\mathrm{Fe}\) is oxidized to \(\mathrm{Fe}^{2+}\) and dissolved oxygen in water is reduced to \(\mathrm{OH}^{-}\) (b) \(\mathrm{Fe}\) is oxidized to \(\mathrm{Fe}^{3+}\) and \(\mathrm{H}_{2} \mathrm{O}\) is reduced to \(\mathrm{O}_{2}^{2-}\) (c) \(\mathrm{Fe}\) is oxidized to \(\mathrm{Fe}^{2+}\) and \(\mathrm{H}_{2} \mathrm{O}\) is reduced to \(\mathrm{O}_{2}\) (d) \(\mathrm{Fe}\) is oxidized to \(\mathrm{Fe}^{2+}\) and \(\mathrm{H}_{2} \mathrm{O}\) is reduced to \(\mathrm{O}_{2}\)

Corrosion of iron is essentially an electrochemical phenomenon where the cell reactions are (a) \(\mathrm{Fe}\) is oxidized to \(\mathrm{Fe}^{2+}\) and dissolved oxygen in water is reduced to \(\mathrm{OH}^{-}\) (b) \(\mathrm{Fe}\) is oxidized to \(\mathrm{Fe}^{3+}\) and \(\mathrm{H}_{2} \mathrm{O}\) is reduced to \(\mathrm{O}_{2}^{2-}\) (c) \(\mathrm{Fe}\) is oxidized to \(\mathrm{Fe}^{2+}\) and \(\mathrm{H}_{2} \mathrm{O}\) is reduced to \(\mathrm{O}_{2}\) (d) \(\mathrm{Fe}\) is oxidized to \(\mathrm{Fe}^{2+}\) and \(\mathrm{H}_{2} \mathrm{O}\) is reduced to \(\mathrm{O}_{2}\)

The standard reduction potentials of \(\mathrm{Zn}^{2+} \mid \mathrm{Zn}\) and \(\mathrm{Cu}^{2+}\) \(\mathrm{Cu}\) are \(-0.76 \mathrm{~V}\) and \(+0.34 \mathrm{~V}\) respectively. What is the cell emf (in V) of the following cell? (RT/F=0.059) \(\mathrm{Zn}\left|\mathrm{Zn}^{2+}(0.05 \mathrm{M}) \| \mathrm{Cu}^{2+}(0.005 \mathrm{M})\right| \mathrm{Cu}\) (a) \(1.1295\) (b) \(1.0705\) (c) \(1.1\) (d) \(1.041\)

\(\mathrm{K}_{\text {p }}\) of \(\mathrm{BaSO}_{4}\) is \(1 \times 10^{-10 .}\) If the ionic conductances of \(\mathrm{Ba}^{+}\)and \(\mathrm{SO}_{4}^{2-}\) ions are 64 and \(80 \mathrm{ohm}^{-1} \mathrm{~cm}^{2} \mathrm{~mol}\) - respectively, then its specific conductance is (a) \(1.44 \times 10^{-8} \mathrm{ohm}^{-1} \mathrm{~cm}^{-1}\) (b) \(144 \times 10^{-8} \mathrm{ohm}^{-1} \mathrm{~cm}^{-1}\) (c) \(1.44 \times 10^{8} \mathrm{ohm}^{-1} \mathrm{~cm}^{-1}\) (d) \(144 \times 10^{8} \mathrm{ohm}^{-1} \mathrm{~cm}^{-1}\)

The reaction potential values of \(\mathrm{M}, \mathrm{N}\) and \(\mathrm{O}\) are \(+2.46,-1.13\) and \(-3.13 \mathrm{~V}\) respectively. Which of the following order is correct, regarding their reducing property? (a) \(\mathrm{O}>\mathrm{N}>\mathrm{M}\) (b) \(\mathrm{O}>\mathrm{M}>\mathrm{N}\) (c) \(\mathrm{M}>\mathrm{N}>\mathrm{O}\) (d) \(\mathrm{M}>\mathrm{O}>\mathrm{N}\)

\(\mathrm{aHNO}_{3}+\mathrm{bH}_{2} \mathrm{~S} \longrightarrow \mathrm{cNO}+\mathrm{d} \mathrm{H}_{2} \mathrm{O}+3 \mathrm{~S}\). What are the values of \(\mathrm{a}, \mathrm{b}, \mathrm{c}, \mathrm{d}\) ? (a) \(2,3,2,2\) (b) \(2,3,2,4\) (c) \(3,3,2,4\) (d) \(4,3,1,2\)

If the aqueous solutions of the following salts are electrolysed for 1 hour with 10 ampere current, which solution will deposit the maximum mass of the metal at the cathode? The atomic weights are \(\mathrm{Fe}=56, \mathrm{Zn}=\) \(65, \mathrm{Ag}=108, \mathrm{Hf}=178\) and \(\mathrm{W}=184\) (a) \(\mathrm{ZnSO}_{4}\) (b) \(\mathrm{FeCl}_{3}\) (c) \(\mathrm{HfCl}_{4}\) (d) \(\mathrm{AgNO}_{3}\)

Given the standard reduction potentials \(\mathrm{Zn}^{2+} / \mathrm{Zn}=\) \(-0.74 \mathrm{~V}, \mathrm{Cl}_{2} / \mathrm{Cl}^{-}=1.36 \mathrm{~V}, \mathrm{H}^{+} 1 / 2 \mathrm{H}_{2}=0 \mathrm{~V}\) and \(\mathrm{Fe}^{2+} / \mathrm{Fe}^{3+}\) \(=0.77 \mathrm{~V}\). The order of increasing strength as reducing agent is (a) \(\mathrm{Zn}, \mathrm{H}_{2}, \mathrm{Fe}^{2+}, \mathrm{Cl}^{-}\) (b) \(\mathrm{H}_{2}, \mathrm{Zn}, \mathrm{Fe}^{2+}, \mathrm{Cl}^{-}\) (c) \(\mathrm{Cl}^{-}, \mathrm{Fe}^{2+}, \mathrm{Zn}, \mathrm{H}_{2}\) (d) \(\mathrm{Cl}^{-} \mathrm{Fe}^{2+}, \mathrm{H}_{2}, \mathrm{Zn}\)

In the electrolytic cell, flow of electrons is from (a) cathode to anode in solution (b) cathode to anode through external supply (c) cathode to anode through internal supply (d) anode to cathode through internal supply

A gas at \(1 \mathrm{~atm}\) is bubbled through a solution containing a mixture of \(1 \mathrm{M} \mathrm{Y}^{-}\)and \(1 \mathrm{M} \mathrm{Z}^{-}\)at \(25^{\circ} \mathrm{C}\). If the reduction potential of \(Z>Y>X\), then (a) \(\mathrm{Y}\) will oxidize \(\mathrm{X}\) and not \(\mathrm{Z}\) (b) \(\mathrm{Y}\) will oxidize \(\mathrm{Z}\) and \(\mathrm{not} \mathrm{X}\)

The oxidation number of sulphur in \(\mathrm{S}_{8}, \mathrm{~S}_{2} \mathrm{~F}_{2}, \mathrm{H}_{2} \mathrm{~S}\) respectively, are (a) \(0,+1\) and \(-2\) (b) \(+2,+1\) and \(-2\) (c) \(0,+1\) and \(+2\) (d) \(-2,+1\) and \(-2\).

A dilute aqueous solution of \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) is electrolyzed using platinum electrodes. The product at the anode and cathode are (a) \(\mathrm{O}_{2}, \mathrm{H}_{2}\) (b) \(\mathrm{S}_{2} \mathrm{O}_{8}^{2-}, \mathrm{Na}\) (c) \(\mathrm{O}_{2}, \mathrm{Na}\) (d) \(\mathrm{S}_{2} \mathrm{O}_{8}^{2-}, \mathrm{H}_{2}\)

The standard reduction potential for \(\mathrm{Fe}^{2+} / \mathrm{Fe}\) and \(\mathrm{Sn}^{2+} /\) Sn electrodes are \(-0.44\) and \(-0.14\) volts respectively. For the cell reaction \(\mathrm{Fe}^{2+}+\mathrm{Sn} \longrightarrow \mathrm{Fe}+\mathrm{Sn}^{2+}\) The standard emf is (a) \(+0.30 \mathrm{~V}\) (b) \(-0.58 \mathrm{~V}\) (c) \(+0.58 \mathrm{~V}\) (d) \(-0.300 \mathrm{~V}\)

The standard oxidation potential \(E^{\circ}\) for the half reactions are as \(\mathrm{Zn} \longrightarrow \mathrm{Zn}^{2+}+2 \mathrm{e}^{-} ; E^{\circ}=+0.76 \mathrm{~V}\) \(\mathrm{Fe} \longrightarrow \mathrm{Fe}^{2+}+2 \mathrm{e} ; E^{\circ}=+0.41 \mathrm{~V}\) The emf for the cell reaction \(\mathrm{Fe}^{2+}+\mathrm{Zn} \longrightarrow \mathrm{Zn}^{2+}+\mathrm{Fe}\) is (a) \(+1.17 \mathrm{~V}\) (b) \(-0.35 \mathrm{~V}\) (c) \(+0.35 \mathrm{~V}\) (d) \(0.117 \mathrm{~V}\)

When a lead storage battery is discharged (a) lead is formed (b) lead sulphate is consumed (c) \(\mathrm{SO}_{2}\) is evolved (d) sulphuric acid is consumed

A solution of sodium sulphate in water is electrolyzed using inert electrodes. The products at the cathode and anode are respectively (a) \(\mathrm{O}_{2}, \mathrm{H}_{2}\) (b) \(\mathrm{O}_{2}, \mathrm{Na}\) (c) \(\mathrm{O}_{2}, \mathrm{SO}_{2}\) (d) \(\mathrm{H}_{2}, \mathrm{O}_{2}\)

A solution containing one mole per litre of each \(\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2} ; \mathrm{AgNO}_{3} ; \mathrm{Hg}_{2}\left(\mathrm{NO}_{3}\right)_{2} ;\) is being electrolyzed by using inert electrodes. The values of standard electrode potentials in volts (reduction potentials) are \(\mathrm{Ag} / \mathrm{Ag}^{+}=+0.80,2 \mathrm{Hg} / \mathrm{Hg}_{2}^{+4}=+0.79\) \(\mathrm{Cu} / \mathrm{Cu}^{+4}=+0.34, \mathrm{Mg} / \mathrm{Mg}^{+}=-2.37\) With increasing voltage, the sequence of deposition of metals on the cathode will be (a) \(\mathrm{Cu}, \mathrm{Hg}, \mathrm{Ag}\) (b) \(\mathrm{Ag}, \mathrm{Hg}, \mathrm{Cu}, \mathrm{Mg}\) (c) \(\mathrm{Mg}, \mathrm{Cu}, \mathrm{Hg}, \mathrm{Ag}\) (d) \(\mathrm{Ag}, \mathrm{Hg}, \mathrm{Cu}\)

The standard reduction potentials at \(298 \mathrm{~K}\) for the following half- reactions are given against each \(\mathrm{Zn}^{2+}(\mathrm{aq})+2 \mathrm{e}=\mathrm{Zn}(\mathrm{s})-0.762\) \(\mathrm{Cr}^{3+}(\mathrm{aq})+2 \mathrm{e}=\mathrm{Cr}(\mathrm{s}) \quad-0.740\) \(2 \mathrm{H}^{+}(\mathrm{aq})+2 \mathrm{e} \rightleftharpoons=\mathrm{H}_{2}(\mathrm{~g}) \quad 0.000\) \(\mathrm{Fe}^{3+}(\mathrm{aq})+2 \mathrm{e}=\mathrm{Fe}^{2+}(\mathrm{aq}) 0.770\) Which is the strongest reducing agent? (a) \(\mathrm{H}_{2}(\mathrm{~g})\) (b) \(\mathrm{Cr}(\mathrm{s})\) (c) \(\mathrm{Zn}(\mathrm{s})\) (d) \(\mathrm{Fe}^{2+}(\mathrm{aq})\) Eor the eon

For the equation \(\mathrm{NO}_{3}^{-}+4 \mathrm{H}^{+}+\mathrm{e}^{-} \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}+\mathrm{NO} .\) The number of electrons in its balanced form would be (a) 6 (b) 4 (c) 3 (d) 9

One litre of \(1 \mathrm{M} \mathrm{CuSO}_{4}\) solution is electrolysed. After passing \(2 \mathrm{~F}\) of electricity, molarity of \(\mathrm{CuSO}_{4}\) solution will be (a) \(\mathrm{M} / 2\) (b) \(\mathrm{M} / 4\) (c) \(\mathrm{M}\) (d) 0

In acidic medium \(\mathrm{MnO}_{4}^{-}\)is an oxidizing agent \(\mathrm{MnO}_{4}^{-}+8 \mathrm{H}^{+}+5 \mathrm{e}^{-} \longrightarrow \mathrm{Mn}^{2+}+4 \mathrm{H}_{2} \mathrm{O} .\) If \(\mathrm{H}^{+}\)ion concentration is doubled, electrode potential of the half cell \(\mathrm{MnO}_{4}^{-}, \mathrm{Mn}^{2+} / \mathrm{Pt}\) will (a) increase by \(28.46 \mathrm{mV}\) (b) decrease by \(28.46 \mathrm{mV}\) (c) increase by \(14.23 \mathrm{mV}\) (d) decrease by \(142.30 \mathrm{mV}\)

In acidic medium \(\mathrm{MnO}_{4}^{-}\)is an oxidizing agent \(\mathrm{MnO}_{4}^{-}+8 \mathrm{H}^{+}+5 \mathrm{e}^{-} \longrightarrow \mathrm{Mn}^{2+}+4 \mathrm{H}_{2} \mathrm{O} .\) If \(\mathrm{H}^{+}\)ion concentration is doubled, electrode potential of the half cell \(\mathrm{MnO}_{4}^{-}, \mathrm{Mn}^{2+} / \mathrm{Pt}\) will (a) increase by \(28.46 \mathrm{mV}\) (b) decrease by \(28.46 \mathrm{mV}\) (c) increase by \(14.23 \mathrm{mV}\) (d) decrease by \(142.30 \mathrm{mV}\)