Chapter 9

Which of the following is a redox reaction? (a) \(\mathrm{NaCl}+\mathrm{KNO}_{3} \longrightarrow \mathrm{NaNO}_{3}+\mathrm{KCl}\) (b) \(\mathrm{CaC}_{2} \mathrm{O}_{4}+2 \mathrm{HCl} \longrightarrow \mathrm{CaCl}_{2}+\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) (c) \(\mathrm{Mg}(\mathrm{OH})_{2}+2 \mathrm{NH}_{4} \mathrm{Cl} \longrightarrow \mathrm{MgCl}_{2}+2 \mathrm{NH}_{4} \mathrm{OH}\) (d) \(\mathrm{Zn}+2 \mathrm{AgCN} \longrightarrow 2 \mathrm{Ag}+\mathrm{Zn}(\mathrm{CN})_{2}\)

Which of the following is not a redox reaction? (a) \(\mathrm{MgCO}_{3} \longrightarrow \mathrm{MgO}+\mathrm{CO}_{2}\) (b) \(\mathrm{O}_{2}+2 \mathrm{H}_{2} \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}\) (c) \(\mathrm{Na}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{NaOH}+1 / 2 \mathrm{H}_{2}\) (d) \(\mathrm{SnCl}_{4} \longrightarrow \mathrm{SnCl}_{2}+\mathrm{Cl}_{2}\)

In the following rection \(4 \mathrm{P}+3 \mathrm{KOH}+3 \mathrm{H}_{2} \mathrm{O} \longrightarrow 3 \mathrm{KH}_{2} \mathrm{PO}_{2}+\mathrm{PH}_{3}\) (a) \(\mathrm{P}\) is only oxidized (b) \(\mathrm{P}\) is only reduced (c) P is both oxidized as well as reduced (d) none of these

The oxidation number of \(\mathrm{V}\) in \(\mathrm{Cs}_{4} \mathrm{Na}\left(\mathrm{HV}_{10} \mathrm{O}_{28}\right)\) is (a) \(+2\) (b) \(+5\) (c) \(-2\) (d) \(+3\)

Given \(E^{\circ}\left(\mathrm{Fe}^{2+} / \mathrm{Fe}\right)=-0.44 \mathrm{~V}\) and \(E^{\circ}\left(\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}\right)=\) \(0.77 \mathrm{~V}\) \(\mathrm{Fe}^{2+}, \mathrm{Fe}^{3+}\) and \(\mathrm{Fe}\) are placed together then (a) \(\mathrm{Fe}^{3+}\) increases (b) \(\mathrm{Fe}^{3+}\) decreases (c) \(\left[\mathrm{Fe}^{3+}\right] /\left[\mathrm{Fe}^{2+}\right]\) remains unchanged (d) \(\mathrm{Fe}^{2+}\) decreases

In electrolyses of \(\mathrm{NaCl}\), when \(\mathrm{Pt}\) electrode is taken then \(\mathrm{H}_{2}\) is liberated at cathode, while with \(\mathrm{Hg}\) cathode it forms sodium amalgam because (a) \(\mathrm{Hg}\) is more inert than \(\mathrm{Pt}\) (b) more voltage is required to reduce \(\mathrm{H}^{+}\)at \(\mathrm{Hg}\) than at \(\mathrm{Pt}\) (c) \(\mathrm{Na}\) is dissolved in \(\mathrm{Hg}\) while it does not dissolve in \(\mathrm{Pt}\) (d) concentration of \(\mathrm{H}^{+}\)ions is larger when \(\mathrm{Pt}\) electrode is taken.

In the silver plating of copper, \(\mathrm{K}\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]\) is used instead of \(\mathrm{AgNO}_{3}\). The reason is (a) a thin layer of \(\mathrm{Ag}\) is formed on \(\mathrm{Cu}\) (b) more voltage is required (c) \(\mathrm{Ag}^{+}\)ions are completely removed from solution (d) less availability of \(\mathrm{Ag}^{+}\)ions, as Cu cannot displace Ag from \(\left[\mathrm{Ag}(\mathrm{CN})_{2}-\right]\) ion

Zn gives \(\mathrm{H}_{2}\) gas with \(\mathrm{H}_{2} \mathrm{SO}_{4}\) and \(\mathrm{HCl}\) but not with \(\mathrm{HNO}_{3}\) because (a) \(\mathrm{Zn}\) acts as oxidizing agent when reacts with \(\mathrm{HNO}_{3}\) (b) \(\mathrm{HNO}_{3}\) is weaker acid then \(\mathrm{H}_{2} \mathrm{SO}_{4}\) and \(\mathrm{HCl}\) (c) in electrochemical series \(\mathrm{Zn}\) is above hydrogen (d) \(\mathrm{NO}_{3}^{-}\)is reduced in preference to hydronium ion

The oxidation state of oxygen in \(\mathrm{O}_{2} \mathrm{PtF}_{6}\) is (a) zero (b) \(-1 / 2\) (c) \(+1 / 2\) (d) \(+1\)

In the reaction, \(\mathrm{I}_{2}+2 \mathrm{~S}_{2} \mathrm{O}_{3}^{2-} \longrightarrow 2 \mathrm{I}^{-}+\mathrm{S}_{4} \mathrm{O}_{6}^{2-}\), equivalent weight of iodine will be equal to (a) twice its molecular weight (b) its molecular weight (c) \(1 / 2\) its moleculear weight (d) \(1 / 4\) its molecular weight

Removal to basic oxide from metal before electroplating is known as (a) poling (b) galvanizing (c) pickling (d) anodizing

Among the following molecules, in which does bromine show the highest oxidation number? (a) \(\mathrm{Hg}_{2}\left(\mathrm{BrO}_{3}\right)_{2}\) (b) \(\mathrm{Br}-\mathrm{Cl}\) (c) \(\mathrm{KBrO}_{4}\) (d) \(\mathrm{Br}_{2}\)

The equivalent weight of \(\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}\) in the reaction \(2 \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}+\mathrm{I}_{2} \longrightarrow \mathrm{Na}_{2} \mathrm{~S}_{4} \mathrm{O}_{6}+2 \mathrm{NaI}\) is \((\mathrm{M}=\) molecular weight \()\) (a) \(\mathrm{M}\) (b) \(\mathrm{M} / 4\) (c) \(\mathrm{M} / 0.5\) (d) \(\mathrm{M} / 2\)

The equivalent weights of \(\mathrm{KMnO}_{4}\) in an acidic, a neutral and a strong alkaline medium respectively are \((\mathrm{M}=\) molecular weight \()\) (a) \(\mathrm{M} / 5, \mathrm{M} / 2, \mathrm{M}\) (b) \(\mathrm{M} / 5, \mathrm{M} / 3, \mathrm{M} / 2\) (c) \(\mathrm{M} / 5, \mathrm{M} / 3, \mathrm{M}\) (d) \(\mathrm{M} / 3, \mathrm{M}, \mathrm{M} / 5\)

When white phosphorus reacts with caustic soda, the products are \(\mathrm{PH}_{3}\) and \(\mathrm{NaH}_{2} \mathrm{PO}_{2} .\) This reaction is an example of (a) oxidation (b) reduction (c) disproportionation (d) neutralization

In the following reaction \(\mathrm{Cr}(\mathrm{OH})_{3}+\mathrm{OH}^{-}+\mathrm{IO}_{3}^{-} \longrightarrow \mathrm{CrO}_{4}^{2-}+\mathrm{H}_{2} \mathrm{O}+\mathrm{I}^{-}\) (a) \(\mathrm{IO}_{3}^{-}\)is oxidizing agent (b) \(\mathrm{Cr}(\mathrm{OH})_{3}\) is oxidized (c) \(6 \mathrm{e}^{-}\)are being taken per 1 atom (d) all are true

The oxidation states of the most electronegative element in the products of the reaction of \(\mathrm{BaO}_{2}\) with dilute \(\mathrm{H}_{2} \mathrm{SO}_{4}\) are (a) 0 and \(-1\) (b) \(-1\) and \(-2\) (c) \(-2\) and 0 (d) \(-2\) and \(+1\)

The brown ring complex compound is formulated as \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{NO}\right] \mathrm{SO}_{4} .\) The oxidation state of iron in the compound is (a) 1 (b) 2 (c) 3 (d) 0

A metal ion \(\mathrm{M}^{3+}\) loses three electrons to produce another cation. The oxidation number of the metal in the cation is (a) \(+3\) (b) \(+4\) (c) \(-3\) (d) \(+6\)

\(\mathrm{A}, \mathrm{B}\) and \(\mathrm{C}\) have the oxidation numbers of \(+6,-2\) and \(-1\) respectively, the possible molecular formula when these atoms combine will be (a) \(\mathrm{A}_{2} \mathrm{BC}\) (b) \(\mathrm{AB}_{2} \mathrm{C}_{2}\) (c) \(\mathrm{ABC}_{2}\) (d) \(\mathrm{AB}_{2} \mathrm{C}\)

Oxidation numbers of carbon in \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}, \mathrm{CH}_{4}\) and diamond respectively are (a) \(+3,4\) and \(+4\) (b) \(+3,-4\) and zero (c) \(+6,+4\) and zero (d) \(+6,+4\) and \(+4\)

Which of the following does not represent redox reactions? (a) \(\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+2 \mathrm{OH}^{-} \longrightarrow \mathrm{CrO}_{4}^{2-}+\mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{SO}_{4}^{2-}+2 \mathrm{I}+2 \mathrm{H}^{+} \longrightarrow \mathrm{I}_{2}+\mathrm{SO}_{4}^{2-}+\mathrm{H}_{2} \mathrm{O}\) (c) \(2 \mathrm{Ca}(\mathrm{OH})_{2}+2 \mathrm{Cl}_{2} \longrightarrow \mathrm{Ca}(\mathrm{ClO})_{2}\) \(+\mathrm{CaCl}_{2}+2 \mathrm{H}_{2} \mathrm{O}\) (d) \(\mathrm{PCl}_{5} \longrightarrow \mathrm{PCl}_{3}+\mathrm{Cl}_{2}\)

If \(\mathrm{Cl}_{2}\) is passed through hot \(\mathrm{NaOH}\), oxidation number of \(\mathrm{Cl}\) changes from (a) \(-1\) to 0 (b) 0 to \(-1\) (c) 0 to \(+5\) (d) 0 to \(+1\)

\(\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+6 \mathrm{I}^{-}+14 \mathrm{H}^{+} \longrightarrow 2 \mathrm{Cr}^{3+}+7 \mathrm{H}_{2} \mathrm{O}+3 \mathrm{I}_{2}\) Equivalent weight of \(\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}\) is (a) \(\mathrm{M} / 3\) (b) \(\mathrm{M} / 6\) (c) \(\mathrm{M} / 2\) (d) none of these

The cell constant of a solution, whose specific conductance and observed conductance are same, is equal to (a) 1 (b) 0 (c) 10 (d) 100

Electrolysis of dilute \(\mathrm{H}_{2} \mathrm{SO}_{4}\) will give (a) \(\mathrm{SO}_{2}\) and \(\mathrm{O}_{2}\) (b) \(\mathrm{H}_{2}\) and \(\mathrm{O}_{2}\) (c) \(\mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{H}_{2}\) (d) \(\mathrm{SO}_{2}\) and \(\mathrm{H}_{2}\)

In the electrolysis of a fused salt, the weight of the deposit on the electrode, will not depend on (a) current intensity (b) electrochemical equivalent of the ions (c) time for electrolysis (d) temperature of the bath

On electrolysis of acidified water, if volume of hydrogen liberated is \(5.6 \mathrm{~cm}^{3}\), then the volume of oxygen liberated equal to (a) \(1.4 \mathrm{~cm}^{3}\) (b) \(2.8 \mathrm{~cm}^{3}\) (c) \(8.2 \mathrm{~cm}^{3}\) (d) \(5.6 \mathrm{~cm}^{3}\)

By removing a salt bridge between the two half cells, the voltage (a) increase gradually (b) increase rapidly (c) does not change (d) drops to zero

The best conductor of electricity is a \(0.1 \mathrm{M}\) solution of (a) \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (b) \(\mathrm{CH}_{3} \mathrm{COOH}\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOH}\) (d) boric acid

For reducing \(1 \mathrm{~mol}\) of \(\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}\) to \(\mathrm{Cr}^{3+}\), the charge required is (a) \(3 \times 96500\) coulomb (b) \(6 \times 96500\) coulomb (c) \(0.3 \mathrm{~F}\) (d) \(0.6 \mathrm{~F}\)

Which of the following reactions is used to make a fuel cell? (a) \(\mathrm{Cd}(\mathrm{s})+2 \mathrm{Ni}(\mathrm{OH})_{3}(\mathrm{~s}) \longrightarrow \mathrm{CdO}(\mathrm{s})\) \(+2 \mathrm{Ni}(\mathrm{OH})_{2}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})\) (b) \(\mathrm{Pb}(\mathrm{s})+\mathrm{PbO}_{2}(\mathrm{~s}) 2 \mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \longrightarrow\) \(2 \mathrm{PbSO}_{4}(\mathrm{~s})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{s})\) (c) \(2 \mathrm{H}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(l)\) (d) \(2 \mathrm{Fe}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g})+4 \mathrm{H}^{+} \longrightarrow 2 \mathrm{Fe}^{2+}(\mathrm{aq})\) \(+2 \mathrm{H}_{2} \mathrm{O}\) (l)

When a Zn strip is placed in \(\mathrm{CuSO}_{4}\) solution, Cu gets precipitated, because standard oxidation potential of \(\mathrm{Zn}\) is (a) \(<\mathrm{Cu}\) (b) \(>\mathrm{Cu}\) (c) \(<\mathrm{SO}_{4}\) (d) \(>\mathrm{SO}_{4}\)

Laws of electrolysis was given by (a) Faraday (b) Ostwald (c) Arrhenius (d) Lamark

In an aqueous solution, hydrogen will not reduce (a) \(\mathrm{Ag}^{+}\) (b) \(\mathrm{Cu}^{2+}\) (c) \(\mathrm{Zn}^{2+}\) (d) \(\mathrm{Fe}^{3+}\)

Aqueous copper sulphate solution is electrolyzed using platinum electrodes. The electrode reaction occurring at cathode is (a) \(\mathrm{Cu}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \longrightarrow \mathrm{Cu}(\mathrm{s})\) (b) \(\mathrm{Cu}(\mathrm{s}) \longrightarrow \mathrm{Cu}^{2+}(\mathrm{aq})+2 \mathrm{e}\) (c) \(2 \mathrm{H}_{2} \mathrm{O}\) (I) \(\longrightarrow \mathrm{O}_{2}(\mathrm{~g})+4 \mathrm{H}^{+}(\mathrm{aq})+4 \mathrm{e}^{-}\) (d) \(\mathrm{O}_{2}(\mathrm{~g})+4 \mathrm{H}^{+}(\mathrm{aq})+4 \mathrm{e}^{-} \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}\) (1)

Molten \(\mathrm{CuCl}_{2}\) is electrolyzed using platinum electrodes. The reaction occurring at anode is (a) \(2 \mathrm{Cl} \longrightarrow \mathrm{Cl}_{2}(\mathrm{~g})+2 \mathrm{e}^{-}\) (b) \(\mathrm{Cl}_{2}(\mathrm{~g})+2 \mathrm{e}^{-} \longrightarrow 2 \mathrm{Cl}\) (c) \(\mathrm{Cu}^{2+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Cu}(\mathrm{s})\) (d) \(\mathrm{Cu}(\mathrm{s}) \longrightarrow \mathrm{Cu}^{2+}+2 \mathrm{e}^{-}\)

When an acid cell is charged, then (a) voltage of cell increases (b) electrolyte of cell dilutes (c) resistance of cell increases (d) none of these

Which one of the following condition will increase the voltage of the cell represented by the equation \(\mathrm{Cu}(\mathrm{s})+2 \mathrm{Ag}^{+}(\mathrm{aq}) \rightleftharpoons \mathrm{Cu}^{2+}(\mathrm{aq})+2 \mathrm{Ag}(\mathrm{s}) ?\) (a) increase in the dimension of Cu electrode (b) increase in the dimension of Ag electrode (c) increase in the concentration of \(\mathrm{Cu}^{2+}\) ions (d) increase in the concentration of \(\mathrm{Ag}^{+}\)ions

Saturated solution of \(\mathrm{KNO}_{3}\) is used to make 'salt bridge' because (a) velocity of \(\mathrm{K}^{+}\)is greater than that of \(\mathrm{NO}_{3}^{-}\) (b) velocity of \(\mathrm{NO}_{3}^{-}\)is greater than that of \(\mathrm{K}^{+}\) (c) velocities of both \(\mathrm{K}^{+}\)and \(\mathrm{NO}_{3}^{-}\)are nearly the same (d) \(\mathrm{KNO}_{3}\) is highly soluble in water

The reaction, \(3 \mathrm{ClO}^{-}(\mathrm{aq}) \longrightarrow \mathrm{ClO}_{3}^{-}(\mathrm{aq})+2 \mathrm{Cl}^{-}(\mathrm{aq})\) is an example of (a) oxidation reaction (b) reduction reaction (c) disproportionation reaction (d) decomposition reaction

The correct order of equivalent conductance at infinite dilution of \(\mathrm{LiCl}, \mathrm{NaCl}\) and \(\mathrm{KCl}\) is (a) \(\mathrm{LiCl}>\mathrm{NaCl}>\mathrm{KCl}\) (b) \(\mathrm{KCl}>\mathrm{NaCl}>\mathrm{LiCl}\) (c) \(\mathrm{NaCl}>\mathrm{KCl}>\mathrm{LiCl}\) (d) \(\mathrm{LiCl}>\mathrm{KCl}>\mathrm{NaCl}\)

The standard reduction potential values of three metallic cations \(\mathrm{X}, \mathrm{Y}\), and \(\mathrm{Z}\) are \(0.52,-3.03\) and \(-1.18\) respectively. The order of reducing power of the corresponding metal is (a) \(\mathrm{Y}>\mathrm{Z}>\mathrm{X}\) (b) \(\mathrm{X}>\mathrm{Y}>\mathrm{Z}\) (c) \(\mathrm{Z}>\mathrm{Y}>\mathrm{X}\) (d) \(\mathrm{Z}>\mathrm{X}>\mathrm{Y}\)

Among the following, identify the species with an atom in \(+6\) oxidation state (a) \(\mathrm{MnO}_{4}^{-}\) (b) \(\mathrm{Cr}(\mathrm{CN})_{6}^{3-}\) (c) \(\mathrm{NiF}_{6}^{2-}\) (d) \(\mathrm{CrO}_{2} \mathrm{Cl}_{2}\)

A standard hydrogen electrode has zero electrode potential because (a) hydrogen is easiest to oxidize (b) its electrode potential is assumed to be zero (c) hydrogen atom has only one electron (d) hydrogen is the lightest element

In the reaction, \(3 \mathrm{Br}_{2}+6 \mathrm{CO}_{3}^{2-}+3 \mathrm{H}_{2} \mathrm{O} \longrightarrow 5 \mathrm{Br}^{-}+\mathrm{BrO}_{3}^{-}+6 \mathrm{HCO}_{3}^{-}\) (a) bromine is oxidized and carbonate is reduced (b) bromine is reduced and water is oxidized (c) bromine is neither reduced nor oxidized (d) bromine is both reduced and oxidized

When a copper wire is placed in a solution of \(\mathrm{AgNO}_{3}\), the solution acquires blue colour. This is due to the formation of (a) \(\mathrm{Cu}^{+}\)ions (b) \(\mathrm{Cu}^{2+}\) ions (c) soluble complex of copper with \(\mathrm{AgNO}_{3}\) (d) Cu ion by the reduction of \(\mathrm{Cu}\)

The electric charge for electrode deposition of one gram equivalent of a substance is (a) charge on one mole of electrons (b) 96500 couloumbs per second (c) one ampere per second (d) one ampere for one hour

The Nernst equation, \(E=E^{\circ}-(\mathrm{RT} / \mathrm{n} F)\) In \(\mathrm{Q}\) indicates that the equilibrium constant \(\mathrm{K}_{c}\) will be equal to Q when (a) \(E=\) zero (b) \(E^{\circ}=1\) (c) \(E=E^{\circ}\) (d) \(\mathrm{RT} / \mathrm{n} F=1\)

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