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Numerical problems in Physical Chemistry for IIT-JEE

P. Bahadur, Shalabh Saxena

Chapter 5

Oxidation-Reduction - all with Video Answers

Educators

Chapter Questions

02:10

Problem 1

Determine the ox. no. of underlined atom in each of the following :
(a) $\mathrm{KCrO}_{3} \mathrm{Cl}$,
(b) $\mathrm{K}_{2} \mathrm{FeO}_{4}$
(c) $\mathrm{Ba}\left(\mathrm{H}_{2} \mathrm{PO}_{2}\right)_{2}$
(d) $\mathrm{Rb}_{4} \mathrm{Na}\left[\mathrm{H} \underline{\mathrm{V}}_{10} \mathrm{O}_{28}\right]$
(e) $\mathrm{Ba}_{2} \mathrm{XeO}_{6}$
(f) $\mathrm{Na}_{2} \mathrm{~S}_{2}$
(g) $\mathrm{K}_{2} \underline{\mathrm{Mn} \mathrm{O}}_{4}$
(h) $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$
(i) $\underline{\mathrm{MnO}_{4}}^{-}$
(j) $\$ \mathrm{O}_{4}^{2-}$
(k) $\mathrm{PO}_{4}^{3-}$
(l) $\mathrm{CO}_{3}^{2-}$
$(\mathrm{m}) \mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}^{2+}$
(n) $\mathrm{Ni}(\mathrm{CO})_{4}$
(o) $\underline{\mathrm{CS}}_{2}$
(p) $\left(\mathrm{NH}_{4}\right)_{6} \mathrm{M}_{7} \mathrm{O}_{24}$
(q) $\left[\mathrm{CoF}_{4}\right]^{-}$
(r) $\underline{\mathrm{O}} \mathrm{s} \mathrm{O}_{\mathbf{4}}$
(s) $\mathrm{Na}_{4} \mathrm{Xe} \mathrm{O}_{\mathrm{b}}$
(t) $\mathrm{KCrO}_{3} \mathrm{Cl}$
(u) $\mathrm{F}_{2} \mathrm{H}_{2}$

Lottie Adams
Lottie Adams
Numerade Educator
02:51

Problem 2

$$
\begin{aligned}
&\text { Find the oxidation number of carbon in the following compounds : }\\
&\left(11,_{3}()\right), \mathrm{CH}_{2} \mathrm{O}, \mathrm{HCOOH}, \mathrm{C}_{2} \mathrm{H}_{2}
\end{aligned}
$$

Vasu Makani
Vasu Makani
Numerade Educator
04:18

Problem 3

$$
\begin{aligned}
&\text { Point out the oxidation number of } \mathrm{C} \text { in the following : }\\
&\mathrm{CH}_{4}, \mathrm{C}_{3} \mathrm{H}_{8}, \mathrm{C}_{2} \mathrm{H}_{6}, \mathrm{C}_{4} \mathrm{H}_{10}, \mathrm{CO}, \mathrm{CO}_{2} \text { and } \mathrm{HCO}_{3}^{-}, \mathrm{CO}_{3}^{2-}
\end{aligned}
$$

Vasu Makani
Vasu Makani
Numerade Educator
03:30

Problem 4

Arrange the following in order of :
(a) Increasing oxidation no. of $\mathrm{Mn}: \mathrm{MnCl}_{2}, \mathrm{MnO}_{2}, \mathrm{Mn}(\mathrm{OH})_{3}, \mathrm{KMnO}_{4}$
(b) Decreasing oxidation no. $X: \quad \mathrm{H} X \mathrm{O}_{4}, \mathrm{H} X \mathrm{O}_{3}, \mathrm{H} \times \mathrm{O}_{2}, \mathrm{H} X \mathrm{O}$
(c) Increasing oxidation no. I: $\quad \mathrm{I}_{2}, \mathrm{HI}, \mathrm{HIO}_{4}, \mathrm{ICl}, \mathrm{IF}_{3}, \mathrm{IF}_{5}$
(d) Increasing oxidation no. of $\mathrm{N}: \mathrm{N}_{2}, \mathrm{NH}_{3}, \mathrm{~N}_{3} \mathrm{H}, \mathrm{NH}_{2} \mathrm{NH}_{2}, \mathrm{NH}_{2} \mathrm{OH}$,
$\mathrm{KNO}_{2}, \mathrm{KNO}_{3}, \mathrm{~N}_{2} \mathrm{O}$

Nidhi Singhi
Nidhi Singhi
Numerade Educator
02:45

Problem 5

Select the nature or type of redox change in the following reactions:
(ii) $2 \mathrm{Cu}^{+} \longrightarrow \mathrm{Cu}^{2+}+\mathrm{Cu}^{0}$
(b) $\quad \mathrm{Cl}_{2} \longrightarrow \mathrm{ClO}^{-}+\mathrm{Cl}^{-}$
(c) $2 \mathrm{KClO}_{3} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{KCl}+3 \mathrm{O}_{2}$
(d) $\quad\left(\mathrm{NH}_{4}\right)_{2} \mathrm{Cr}_{2} \mathrm{O}_{7} \longrightarrow \mathrm{N}_{2}+\mathrm{Cr}_{2} \mathrm{O}_{3}+4 \mathrm{H}_{2} \mathrm{O}$
(e) $10 \mathrm{FeSO}_{4}+2 \mathrm{KMnO}_{4}+8 \mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow 2 \mathrm{MnSO}_{4}+5 \mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}+$
$\mathrm{K}_{2} \mathrm{SO}_{4}+8 \mathrm{H}_{2} \mathrm{O}$
(f) $5 \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}+2 \mathrm{KMnO}_{4}+3 \mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{K}_{2} \mathrm{SO}_{4}+2 \mathrm{MnSO}_{4}+$
$10 \mathrm{CO}_{2}+8 \mathrm{H}_{2} \mathrm{O}$

Nidhi Singhi
Nidhi Singhi
Numerade Educator
02:39

Problem 6

Identify the oxidised and reduced species in the following reactions:
a) $\mathrm{CH}_{4(\mathrm{~g})}+4 \mathrm{Cl}_{2(\mathrm{~g})} \longrightarrow \mathrm{CCl}_{4(\mathrm{~g})}+4 \mathrm{HCl}_{(\mathrm{g})}$
c) $\mathrm{I}_{2 \text { (aq.) }}+2 \mathrm{~S}_{2} \mathrm{O}_{3}{ }^{2-}(\mathrm{aq}) \longrightarrow 2 \Gamma_{(\mathrm{aq} .)}+\mathrm{S}_{4} \mathrm{O}_{6}^{2-}$
(d) $\mathrm{Cl}_{2(\mathrm{~g})}+2 \mathrm{Br}_{\text {(aq.) }}^{-} \longrightarrow 2 \mathrm{Cl}^{-}_{\text {(aq.) }}+\mathrm{Br}_{2(\mathrm{aq} .)}$

Nidhi Singhi
Nidhi Singhi
Numerade Educator
01:56

Problem 7

Identify the substance acting as oxidunt or reductant if any in the following:
(i) $\mathrm{AICl}_{3}+3 \mathrm{~K} \longrightarrow \mathrm{Al}+3 \mathrm{KCI}$
(ii) $\mathrm{SO}_{2}+2 \mathrm{H}_{2} \mathrm{~S} \longrightarrow 3 \mathrm{~S}+\mathrm{H}_{2} \mathrm{O}$
(iii) $\mathrm{BaCl}_{2}+\mathrm{Na}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{BaSO}_{4}+2 \mathrm{NaCl}$
(iv) $3 \mathrm{I}_{2}+6 \mathrm{NaOH} \longrightarrow \mathrm{NalO}_{3}+5 \mathrm{NaI}+3 \mathrm{H}_{2} \mathrm{O}$

Nidhi Singhi
Nidhi Singhi
Numerade Educator
03:27

Problem 8

Write the half reactions for the following redox reactions:
(a) $2 \mathrm{Fe}^{3+}{ }_{\text {(aq. })}+2 \mathrm{I}_{(\mathrm{aq})} \longrightarrow 2 \mathrm{Fe}^{2+}{ }_{\text {(aq.) }}+\mathrm{I}_{2(\mathrm{aq} .)}$
(b) $\mathrm{Zn}_{(\mathrm{s})}+2 \mathrm{H}_{(\text {aq. })}^{+} \longrightarrow \mathrm{Zn}^{2+}$ (aq.) $+\mathrm{H}_{2(\mathrm{~g})}$
(c) $\mathrm{Al}_{(\mathrm{s})}+3 \mathrm{Ag}^{+}{ }_{\text {(aq.) }} \longrightarrow \mathrm{Al}_{\text {(aq.) }}^{3+}+3 \mathrm{Ag}_{(\mathrm{s})}$

Vasu Makani
Vasu Makani
Numerade Educator
02:54

Problem 9

How many mole of electrons are involved in balancing the following equations :
(a) $\mathrm{H}_{2} \mathrm{~S}+\mathrm{NO}_{3}^{-} \longrightarrow \mathrm{S}+\mathrm{NO}$
(b) $\mathrm{Mn}(\mathrm{OH})_{2}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow \mathrm{MnO}_{2}+2 \mathrm{H}_{2} \mathrm{O}$
(c) $\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+\mathrm{Fe}^{2+}+\mathrm{C}_{2} \mathrm{O}_{4}^{2-} \longrightarrow \mathrm{Cr}^{3+}+\mathrm{Fe}^{3+}+\mathrm{CO}_{2}$ (acid medium)
(d) $\mathrm{Br}_{2}+\mathrm{OH} \stackrel{-}{\longrightarrow} \mathrm{BrO}_{3}^{-}+\mathrm{Br}^{-}$

Nidhi Singhi
Nidhi Singhi
Numerade Educator
03:03

Problem 10

$$
\begin{aligned}
&\text { How many mole of } \mathrm{FeSO}_{4}, \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} \text { and } \mathrm{FeC}_{2} \mathrm{O}_{4} \text { are oxidised }\\
&\text { separately by one mole of } \mathrm{KMnO}_{4} \text { in acid medium. }
\end{aligned}
$$

Nidhi Singhi
Nidhi Singhi
Numerade Educator