Chapter 8

The compound that cannot act both as oxidising and reducing agent is: [Main Jan. 09, 2020 (I)] (a) \(\mathrm{H}_{3} \mathrm{PO}_{4}\) (b) \(\mathrm{HNO}_{2}\) (c) \(\mathrm{H}_{2} \mathrm{SO}_{3}\) (d) \(\mathrm{H}_{2} \mathrm{O}_{2}\)

Oxidation number of potassium in \(\mathrm{K}_{2} \mathrm{O}, \mathrm{K}_{2} \mathrm{O}_{2}\) and \(\mathrm{KO}_{2}\), respectively, is: \(\quad\) [Main Jan. 07, 2020 (I)] (a) \(+2,+1\) and \(+\frac{1}{2}\) (b) \(+1,+1\) and \(+1\) (c) \(+1,+4\) and \(+2\) (d) \(+1,+2\) and \(+4\)

Given : \(\mathrm{Co}^{3+}+\mathrm{e}^{-} \rightarrow \mathrm{Co}^{2+} ; \mathrm{E}^{\circ}=+1.81 \mathrm{~V}\) \(\mathrm{Pb}^{4+}+2 \mathrm{e}^{-} \rightarrow \mathrm{Pb}^{2+} ; \mathrm{E}^{0}=+1.67 \mathrm{~V}\) \(\mathrm{Ce}^{4+}+\mathrm{e}^{-} \rightarrow \mathrm{Ce}^{3+} ; \mathrm{E}^{0}=+1.61 \mathrm{~V}\) \(\mathrm{Bi}^{3+}+3 \mathrm{e}^{-} \rightarrow \mathrm{Bi} ; \mathrm{E}^{\circ}=+0.20 \mathrm{~V}\) oxidizing power of the species will increase in the order: (a) \(\mathrm{Ce}^{4+}<\mathrm{Pb}^{4+}<\mathrm{Bi}^{3+}<\mathrm{Co}^{3+}\) (b) \(\mathrm{Bi}^{3+}<\mathrm{Ce}^{4+}<\mathrm{Pb}^{4+}<\mathrm{Co}^{3+}\) (c) \(\mathrm{Co}^{3+}<\mathrm{Ce}^{4+}<\mathrm{Bi}^{3+}<\mathrm{Pb}^{4+}\) (d) \(\mathrm{Co}^{3+}<\mathrm{Pb}^{4+}<\mathrm{Ce}^{4+}<\mathrm{Bi}^{3+}\)

The redox reaction among the following is: [Main Jan. 07, 2020 (II)] (a) formation of ozone from atmospheric oxygen in the presence of sunlight (b) reaction of \(\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{Cl}_{3}\) with \(\mathrm{AgNO}_{3}\) (c) reaction of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) with \(\mathrm{NaOH}\) (d) combination of dinitrogen with dioxygen at \(2000 \mathrm{~K}\)

An example of a disproportionation reaction is: [Main April 12, 2019 (I)] (a) \(2 \mathrm{MnO}_{4}+10 \mathrm{I}^{-}+16 \mathrm{H}^{+} \rightarrow 2 \mathrm{Mn}^{2+}+5 \mathrm{I}_{2}+8 \mathrm{H}_{2} \mathrm{O}\) (b) \(2 \mathrm{NaBr}+\mathrm{Cl}_{2} \rightarrow 2 \mathrm{NaCl}+\mathrm{Br}_{2}\) (c) \(2 \mathrm{KMnO}_{4} \rightarrow \mathrm{K}_{2} \mathrm{MnO}_{4}+\mathrm{MnO}_{2}+\mathrm{O}_{2}\) (d) \(2 \mathrm{CuBr} \rightarrow \mathrm{CuBr}_{2}+\mathrm{Cu}\)

Given that \(\mathrm{E}_{\mathrm{O}_{2} / \mathrm{H}_{2} \mathrm{O}}^{\circ}=+1.23 \mathrm{~V} ;\) \(\mathrm{E}_{\mathrm{S}_{2} \mathrm{O}_{8}^{2-} / \mathrm{SO}_{4}^{2-}}=2.05 \mathrm{~V}\) \(\mathrm{E}_{\mathrm{Br}_{2} / \mathrm{Br}^{-}}^{\circ}=+1.09 \mathrm{~V}\) \(\mathrm{E}_{\mathrm{Au}^{3+} / \mathrm{Au}}^{\circ}=+1.4 \mathrm{~V}\) The strongest oxidising agent is : (a) \(\mathrm{Au}^{3+}\) (b) \(\mathrm{O}_{2}\) (c) \(\mathrm{S}_{2} \mathrm{O}_{8}^{2-}\) (d) \(\mathrm{Br}_{2}\)

Which of the following reactions is an example of a redox reaction? [Main 2017] (a) \(\mathrm{XeF}_{4}+\mathrm{O}_{2} \mathrm{~F}_{2} \rightarrow \mathrm{XeF}_{6}+\mathrm{O}_{2}\) (b) \(\mathrm{XeF}_{2}+\mathrm{PF}_{5} \rightarrow[\mathrm{XeF}]^{+} \mathrm{PF}_{6}^{-}\) (c) \(\mathrm{XeF}_{6}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{XeOF}_{4}+2 \mathrm{HF}\) (d) \(\mathrm{XeF}_{6}+2 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{XeO}_{2} \mathrm{~F}_{2}+4 \mathrm{HF}\)

Consider the following reduction processes: \(\mathrm{Zn}^{2+}+2 \mathrm{e}^{-} \square \mathrm{Zn}(\mathrm{s}) ; \mathrm{E}^{\circ}=-0.76 \mathrm{~V}\) \(\mathrm{Ca}^{2+}+2 \mathrm{e}^{-} \square \mathrm{Ca}(\mathrm{s}) ; \mathrm{E}^{\circ}=-2.87 \mathrm{~V}\) \(\mathrm{Mg}^{2+}+2 \mathrm{e}^{-} \square \mathrm{Mg}(\mathrm{s}) ; \mathrm{E}^{\circ}=-2.36 \mathrm{~V}\) \(\mathrm{Ni}^{2+}+2 \mathrm{e}^{-} \square \mathrm{Ni}(\mathrm{s}) ; \mathrm{E}^{\circ}=-0.25 \mathrm{~V}\) The reducing power of the metals increases in the order: (a) \(\mathrm{Ca}<\mathrm{Zn}<\mathrm{Mg}<\mathrm{Ni}\) (b) \(\mathrm{Ni}<\mathrm{Zn}<\mathrm{Mg}<\mathrm{Ca}\) (c) \(\mathrm{Zn}<\mathrm{Mg}<\mathrm{Ni}<\mathrm{Ca}\) (d) \(\mathrm{Ca}<\mathrm{Mg}<\mathrm{Zn}<\mathrm{Ni}\)

Copper becomes green when exposed to moist air for a long period. This is due to: [Main Online April 12, 2014] (a) the formation of a layer of cupric oxide on the surface of copper. (b) the formation of a layer of basic carbonate of copper on the surface of copper. (c) the formation of a layer of cupric hydroxide on the surface of copper. (d) the formation of basic copper sulphate layer on the surface of the metal.

The oxidation states of \(\mathrm{Cr}\) in \(\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{Cl}_{3}, \quad\left[\mathrm{Cr}\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)_{2}\right]\), and \(\mathrm{K}_{2}\left[\mathrm{Cr}(\mathrm{CN})_{2}(\mathrm{O})_{2}\left(\mathrm{O}_{2}\right)\left(\mathrm{NH}_{3}\right)\right]\) respectively are : [Main 2018] (a) \(+3,+4\), and \(+6\) (b) \(+3\), \(+2\), and \(+4\) (c) \(+3,0\), and \(+6\) (d) \(+3,0\), and \(+4\)

In the reaction of oxalate with permanganate in acidic medium, the number of electrons involved in producing one molecule of \(\mathrm{CO}_{2}\) is: (a) 1 (b) 10 (c) 2 (d) 5

Amongst the following, identify the species with an atom in \(+6\) oxidation state: \(\quad[\) Main Online April 19, 2014] (a) \(\left[\mathrm{MnO}_{4}\right]^{-}\) (b) \(\left[\mathrm{Cr}(\mathrm{CN})_{6}\right]^{3-}\) (c) \(\mathrm{Cr}_{2} \mathrm{O}_{3}\) (d) \(\mathrm{CrO}_{2} \mathrm{Cl}_{2}\)

In which of the following reactions, hydrogen peroxide acts as an oxidizing agent ? [Main Online April 8, 2017] (a) \(\mathrm{HOCl}+\mathrm{H}_{2} \mathrm{O}_{2} \rightarrow \mathrm{H}_{3} \mathrm{O}^{+}+\mathrm{Cl}^{-}+\mathrm{O}_{2}\) (b) \(\mathrm{I}_{2}+\mathrm{H}_{2} \mathrm{O}_{2}+2 \mathrm{OH}^{-} \rightarrow 2 \mathrm{I}^{-}+2 \mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}\) (c) \(2 \mathrm{MnO}_{4}^{-}+3 \mathrm{H}_{2} \mathrm{O}_{2} \rightarrow 2 \mathrm{MnO}_{2}+3 \mathrm{O}_{2}+2 \mathrm{H}_{2} \mathrm{O}+2 \mathrm{OH}^{-}\) (d) \(\mathrm{PbS}+4 \mathrm{H}_{2} \mathrm{O}_{2} \rightarrow \mathrm{PbSO}_{4}+4 \mathrm{H}_{2} \mathrm{O}\)

Consider the reaction: $$ \begin{aligned} &\mathrm{H}_{2} \mathrm{SO}_{3}(\mathrm{aq})+\mathrm{Sn}^{4+}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \\ &\quad \rightarrow \mathrm{Sn}^{2+}(\mathrm{aq})+\mathrm{HSO}_{4}^{-}(\mathrm{aq})+3 \mathrm{H}^{+}(\mathrm{aq}) \end{aligned} $$ Which of the following statements is correct? (a) \(\mathrm{Sn}^{4+}\) is the oxidizing agent because it undergoes oxidation (b) \(\mathrm{Sn}^{4+}\) is the reducing agent because it undergoes oxidation (c) \(\mathrm{H}_{2} \mathrm{SO}_{3}\) is the reducing agent because it undergoes oxidation (d) \(\mathrm{H}_{2} \mathrm{SO}_{3}\) is the reducing agent because it undergoes reduction

In the following balanced reaction, \(\mathrm{X} \mathrm{MnO}_{4}^{-}+\mathrm{Y} \mathrm{C}_{2} \mathrm{O}_{4}^{2-}+\mathrm{ZH}^{+}\) $$ \rightleftharpoons \mathrm{XMn}^{2+}+2 \mathrm{Y} \mathrm{CO}_{2}+\frac{\mathrm{Z}}{2} \mathrm{H}_{2} \mathrm{O} $$ values of \(X, Y\) and \(Z\) respectively are [Main Online May 12, 2012; 2013] (a) \(2,5,16\) (b) \(8,2,5\) (c) \(5,2,16\) (d) \(5,8,4\)

Which one of the following cannot function as an oxidising agent ? (a) \(\mathrm{I}^{-}\) (b) \(\mathrm{S}(\mathrm{s})\) (c) \(\mathrm{NO}_{3}^{-}\)(aq) (d) \(\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}\)

Oxidation state of sulphur in anions \(\mathrm{SO}_{3}^{2-}, \mathrm{S}_{2} \mathrm{O}_{4}^{2-}\) and \(\mathrm{S}_{2} \mathrm{O}_{6}^{2-}\) increases in the orders : [Main Online April 22, 2013] (a) \(\mathrm{S}_{2} \mathrm{O}_{6}^{2-}<\mathrm{S}_{2} \mathrm{O}_{4}^{2-}<\mathrm{SO}_{3}^{2-}\) (b) \(\mathrm{SO}_{6}^{2-}<\mathrm{S}_{2} \mathrm{O}_{4}^{2-}<\mathrm{S}_{2} \mathrm{O}_{6}^{2-}\) (c) \(\mathrm{S}_{2} \mathrm{O}_{4}^{2-}<\mathrm{SO}_{3}^{2-}<\mathrm{S}_{2} \mathrm{O}_{6}^{2-}\) (d) \(\mathrm{S}_{2} \mathrm{O}_{4}^{2-}<\mathrm{S}_{2} \mathrm{O}_{6}^{2-}<\mathrm{SO}_{3}^{2-}\)

Consider a titration of potassium dichromate solution with acidified Mohr's salt solution using diphenylamine as indicator. The number of moles of Mohr's salt required per mole of dichromate is [2007] (a) 3 (b) 4 (c) 5 (d) 6

\(\left[\mathrm{Co}(\mathrm{CN})_{6}\right]^{3-}, \mathrm{Mh} \mathrm{O}_{3}\) The reaction, \(3 \mathrm{ClO}^{-}(\mathrm{aq}) \longrightarrow \mathrm{ClO}_{3}^{-}(\mathrm{aq})+\) \(2 \mathrm{Cl}^{-}(\mathrm{aq})\), is an example of [2001S] (a) oxidation reaction (b) reduction reaction (c) disproportionation reaction (d) decomposition reaction

Amongst the following identify the species with an atom in \(+6\) oxidation state [2000S] (a) \(\mathrm{MnO}_{4}^{-}\) (b) \(\mathrm{Cr}(\mathrm{CN})_{6}^{3-}\) (c) \(\mathrm{NiF}_{6}^{2-}\) (d) \(\mathrm{CrO}_{2} \mathrm{Cl}_{2}\)

The oxidation number of sulphur in \(\mathrm{S}_{8}, \mathrm{~S}_{2} \mathrm{~F}_{2}, \mathrm{H}_{2} \mathrm{~S}\) respectively, are [1999-2 Marks] (a) \(0,+1\) and \(-2\) (b) \(+2,+1\) and \(-2\) (c) \(0,+1\) and \(+2\) (d) \(-2,+1\) and \(-2\)

The oxidation states of the most electronegative element in the products of the reaction, \(\mathrm{BaO}_{2}\) with dil. \(\mathrm{H}_{2} \mathrm{SO}_{4}\) is [1991-1 Mark] (a) 0 and \(-1\) (b) \(-1\) and \(-2\) (c) \(-2\) and 0 (d) \(-2\) and \(+1\)

The oxidation number of phosphorus in \(\mathrm{Ba}\left(\mathrm{H}_{2} \mathrm{PO}_{2}\right)_{2}\) is : (a) \(+3\) (b) \(+2\) (c) \(+1\) (d) \(-1\)

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 is : [1987-1 Mark] (a) 1 (b) 2 (c) 3 (d) 0

The oxidation number of carbon in \(\mathrm{CH}_{2} \mathrm{O}\) is (a) \(-2\) (b) \(+2\) (c) 0 (d) \(+4\)

One mole of \(\mathrm{N}_{2} \mathrm{H}_{4}\) loses ten moles of electrons to form a new compound \(Y\). Assuming that all the nitrogen appears in the new compound, what is the oxidation state of nitrogen in \(Y\) ? (There is no change in the oxidation state of hydrogen). [1981 - 1 Mark] (a) \(-1\) (b) \(-3\) (c) \(+3\) (d) \(+5\)

The difference in the oxidation numbers of the two types of sulphur atoms in \(\mathrm{Na}_{2} \mathrm{~S}_{4} \mathrm{O}_{6}\) is

Consider the following equations: \(2 \mathrm{Fe}^{2+}+\mathrm{H}_{2} \mathrm{O}_{2} \rightarrow x \mathrm{~A}+y \mathrm{~B}\) (in basic medium) \(2 \mathrm{MnO}_{4}^{-}+6 \mathrm{H}^{+}+5 \mathrm{H}_{2} \mathrm{O}_{2} \rightarrow x^{\prime} \mathrm{C}+y^{\prime} \mathrm{D}+z^{\prime} \mathrm{E}\) (in acidic medium) The sum of the stoichiometric coefficients \(x, y, x^{\prime}, y^{\prime}\) and \(z^{\prime}\) for products \(\mathrm{A}\), \(\mathrm{B}, \mathrm{C}, \mathrm{D}\) and \(\mathrm{E}\), respectively, is

The oxidation states of transition metal atoms in \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}, \mathrm{KMnO}_{4}\) and \(\mathrm{K}_{2} \mathrm{FeO}_{4}\), respectively, are \(x, y\) and \(z\). The sum of \(x, y\) and \(z\) is

The compound \(\mathrm{YBa}_{2} \mathrm{Cu}_{3} \mathrm{O}_{7}\), which shows super-conductivity, has copper in oxidation state \(\ldots \ldots \ldots \ldots \ldots \ldots\), assume that the rare earth element yttrium is in its usual \(+3\) oxidation state.

Arrange the following in increasing oxidation number of iodine. [1986-1 Mark] \(\mathrm{I}_{2}, \mathrm{HI}, \mathrm{HIO}_{4}, \mathrm{ICl}\)

Balance the following equations. (i) \(\mathrm{Cu}_{2} \mathrm{O}+\mathrm{H}^{+}+\mathrm{NO}_{3}^{-} \rightarrow \mathrm{Cu}^{2+}+\mathrm{NO}+\mathrm{H}_{2} \mathrm{O}\) (ii) \(\left.\mathrm{K}_{4} \mathrm{Fe}(\mathrm{CN})_{6}\right]+\mathrm{H}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O}\) \(\quad \rightarrow \mathrm{K}_{2} \mathrm{SO}_{4}+\mathrm{FeSO}_{4}+\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}+\mathrm{CO}\) (iii) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}+\mathrm{I}_{2}+\mathrm{OH}^{-} \rightarrow \mathrm{CHI}_{3}+\mathrm{HCO}_{3}^{-}+\mathrm{I}^{-}+\mathrm{H}_{2} \mathrm{O}\)