Chapter 8

The e:m.f. of the following galvanic cells: (a) \(\mathrm{Zn}\left|\mathrm{Zn}^{2+}(1 M) \| \mathrm{Cu}^{2+}(1 M)\right| \mathrm{Cu}\) (b) \(\mathrm{Zn}\left|\mathrm{Zn}^{2+}(0.1 M) \| \mathrm{Cu}^{2+}(1 M)\right| \mathrm{Cu}\) (c) \(\mathrm{Zn}\left|\mathrm{Zn}^{2+}(1 M) \| \mathrm{Cu}^{2+}(0.1 M)\right| \mathrm{Cu}\) (d) \(\mathrm{Zn}\left|\mathrm{Zn}^{2+}(0.1 M) \| \mathrm{Cu}^{2+}(0.1 M)\right| \mathrm{Cu}\) are represented by \(E_{1}, E_{2}, E_{3}\) and \(E_{4}\) respectively. Which of the following statement is true? (a) \(E_{1}>E_{2}>E_{3}>E_{4}\) (b) \(E_{3}>E_{2}>E_{1}>E_{4}\) (c) \(E_{3}>E_{1}=E_{4}>E_{2}\) (d) \(E_{2}>E_{1}=E_{4}>E_{3}\)

Given the listed standard electrode potentials, what is \(E^{\circ}\) for the cell : \(4 \mathrm{BiO}^{+}(a q)+3 \mathrm{~N}_{2} \mathrm{H}_{5}^{+}(a q) \longrightarrow 4 \mathrm{Bi}(s)+3 \mathrm{~N}_{2}(g)+4 \mathrm{H}_{2} \mathrm{O}(l)+7 \mathrm{H}^{+}(a q)\) \(\mathrm{N}_{2}(g)+5 \mathrm{H}^{+}(a q)+4 e^{-} \longrightarrow \mathrm{N}_{2} \mathrm{H}_{5}^{+}(a q), E^{\circ}=-0.23 \mathrm{~V}\) \(\mathrm{BiO}^{+}(a q)+2 \mathrm{H}^{+}(a q)+3 e^{-} \longrightarrow \mathrm{Bi}(s)+\mathrm{H}_{2} \mathrm{O}(l), \quad E^{\circ}=+0.32 \mathrm{~V}\) (a) \(+0.55\) (b) \(+0.34\) (c) \(+1.88\) (d) \(+0.09\)

The \(E^{\circ}\) for the following cell is \(+0.34 \mathrm{~V} . \operatorname{In}(s)\left|\ln (\mathrm{OH})_{3}(a q) \| \mathrm{SbO}_{2}^{-}(a q)\right| \mathrm{Sb}(s)\). Using \(E^{\circ}=-1.0 \mathrm{~V}\) for the \(\operatorname{In}(\mathrm{OH})_{3} \mid\) In couple, calculate \(E^{\circ}\) for the \(\mathrm{SbO}_{2}^{-} \mid \mathrm{Sb}\) half-reaction : (a) \(-1.34\) (b) \(+0.66\) (c) \(+0.82\) (d) \(-0.66\)

The position of some metals in the electrochemical series in decreasing electropositive character is \(\mathrm{Mg}>\mathrm{Al}>\mathrm{Zn}>\mathrm{Cu}>\mathrm{Ag}\). What will happened if copper spoon is used to stirred a solution of aluminium nitrate ? (a) The spoon gets coated with aluminium. (b) An alloy of aluminium and copper is formed. (c) No reaction occurs (d) The solution starts turning blue

Zn can displace : (a) \(\mathrm{Mg}\) from its aqueous solution (b) Cu from its aqueous solution (c) Na from its aqueous solution (d) Al from its aqueous solution

Based on the following information arrange four metals \(A, B, C\) and \(D\) in order of decreasing ability to act as reducing agents: (I) Only \(A, B\) and \(C\) react with \(1 M \mathrm{HCl}\) to give \(\mathrm{H}_{2}(g)\) (II) When \(C\) is added to solutions of the other metal ions, metallic \(B\) and \(D\) are formed (III) Metal \(C\) does not reduce \(A^{n+}\). (a) \(C>A>B>D\) (b) \(C>A>D>B\) (c) \(A>C>D>B\) (d) \(A>C>B>D\)

Based on the following information arrange four metals, \(A, B, C\) and \(D\) in order of increasing ability to act as reducing agents : (I) Only \(C\) react with \(1 M \mathrm{HCl}\) to give \(\mathrm{H}_{2}(g)\) (II) When \(A\) is added to solution of the other metal ions, metallic \(D\) is formed but not \(B\) or \(C\) (a) \(D

The standard potential at \(25^{\circ} \mathrm{C}\) for the following half reactions is given : $$ \begin{aligned} \mathrm{Zn}^{2+}+2 e^{-} & \mathrm{Zn} ; E^{\circ}=-0.762 \mathrm{~V} \\ \mathrm{Mg}^{2+}+2 e^{-} & \mathrm{Mg} ; E^{\circ}=-2.37 \mathrm{~V} \end{aligned} $$ When Zinc dust is added to the solution of \(\mathrm{MgCl}_{2}\). (a) \(\mathrm{ZnCl}_{2}\) is formed (b) \(\mathrm{Mg}\) is precipitated (c) Zn dissolved in the solution (d) No reaction takes place

The element which can displace three other halogens from their compound is : (a) \(\mathrm{F}\) (b) \(\mathrm{Cl}\) (c) \(\mathrm{Br}\) (d) I

The \(E^{\circ}\) at \(25 C^{\circ}\) for the following reaction is \(0.55 \mathrm{~V}\). Calculate the \(\Delta G^{\circ}\) in \(\mathrm{kJ}\) : \(4 \mathrm{BiO}^{+}(a q)+3 \mathrm{~N}_{2} \mathrm{H}_{5}^{+} \longrightarrow 4 \mathrm{Bi}(s)+3 \mathrm{~N}_{2}(g)+4 \mathrm{H}_{2} \mathrm{O}(l)+7 \mathrm{H}^{+}\) (a) \(-637\) (b) \(-424\) (c) \(-106\) (d) \(-318.5\)