Problem 1
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) \(\mathrm{Zn}+2 \mathrm{AgCN} \longrightarrow 2 \mathrm{Ag}+\mathrm{Zn}(\mathrm{CN})_{2}\)
Problem 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) \(\mathrm{SnCl}_{4} \longrightarrow \mathrm{SnCl}_{2}+\mathrm{Cl}_{2}\)
Problem 3
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
Problem 4
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) \(+3\)
Problem 6
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
Problem 8
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.
Problem 9
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
Problem 10
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
Problem 11
The oxidation state of oxygen in \(\mathrm{O}_{2} \mathrm{PtF}_{6}\) is (a) zero (b) \(-1 / 2\) (c) \(+1 / 2\) (d) \(+1\)
Problem 13
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
