Zinc oxide loses oxygen on heating according to the reaction

$\mathrm{ZnO} \stackrel{\mathrm{Heat}}{\to } {\mathrm{Zn}}^{2+} + \frac{1}{2}{\mathrm{O}}_2 + 2{\mathrm{e}}^{-}$

It becomes yellow on heating because

• Zn²⁺ ions and electrons move too interstitial sites and F-centres are created.

• Oxygen and electron moves at the crystal and ions become yellow

• Zn²⁺ again combine with oxygen to give yellow oxide

• Zn²⁺ are replaced by oxygen.

Which of the following reactions depict the oxidising behavior of H₂SO₄?

• $2{\mathrm{PCl}}_5 + {\mathrm{H}}_2{\mathrm{SO}}_4 \to 2{\mathrm{POCl}}_3 + 2\mathrm{HCl} +{\mathrm{SO}}_2{\mathrm{Cl}}_2$

• $2\mathrm{NaOH} + {\mathrm{H}}_2{\mathrm{SO}}_4 \to {\mathrm{Na}}_2{\mathrm{SO}}_4 + 2{\mathrm{H}}_2\mathrm{O}$

• $\mathrm{NaCl} + {\mathrm{H}}_2{\mathrm{SO}}_4 \to {\mathrm{NaHSO}}_4 + \mathrm{HCl}$

• $2\mathrm{HI} +{\mathrm{H}}_2{\mathrm{SO}}_4 \to {\mathrm{I}}_2 + {\mathrm{SO}}_{2 }+ 2{\mathrm{H}}_2\mathrm{O}$

When 96.5 C of electricity is passed through a solution of silver nitrate (at wt. of Ag = 107. 8 7 which is approx. 108), the amount of silver deposted is

• 5.8 mg

• 10.8 mg

• 15.8 mg

• 20.8 mg

The standard reduction potentials at 298 K for the following half reactions are given against each

                          $$\begin{gathered} {\mathrm{Zn}}^{2+}\left(\mathrm{aq}\right) + 2{\mathrm{e}}^{-} \rightleftharpoons \mathrm{Zn}\left(\mathrm{s}\right) -0.762 \mathrm{V} \\ {\mathrm{Cr}}^{3+}\left(\mathrm{aq}\right) + 2{\mathrm{e}}^{-} \rightleftharpoons \mathrm{Cr}\left(\mathrm{s}\right) - 0.740 \mathrm{V} \\ 2{\mathrm{H}}^{+}\left(\mathrm{aq}\right) + 2{\mathrm{e}}^{-} \rightleftharpoons {\mathrm{H}}_2\left(\mathrm{s}\right) 0.000 \mathrm{V} \\ {\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right) + 2{\mathrm{e}}^{-} \rightleftharpoons {\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right) 0.770 \mathrm{V} \end{gathered}$$

Which is the strongest reducing agent ?

• Zn(s)

• Cr(s)

• H₂(s)

• Fe²⁺ (aq)

$\mathrm{For} \mathrm{the} \mathrm{reaction}, 2{\mathrm{NO}}_2+ {\mathrm{F}}_2\to 2{\mathrm{NO}}_2\mathrm{F},$ following mechanism has been provided. 

$$\begin{gathered} {\mathrm{NO}}_2+ {\mathrm{F}}_2 \stackrel{\mathrm{slow}}{\to } {\mathrm{NO}}_2\mathrm{F} + \mathrm{F} \\ {\mathrm{NO}}_2+ {\mathrm{F}}_2 \stackrel{\mathrm{Fast}}{\to } {\mathrm{NO}}_2\mathrm{F} \end{gathered}$$

Thus, rate expression of the above reaction can be written as

• r =k [NO₂]²[F₂]

• r= k [NO₂] [F₂]

• r= k [NO₂]

• r= k [F₂]

For a reaction,  ${\mathrm{I}}^{-}+ {\mathrm{OCl}}^{-} \to {\mathrm{IO}}^{-} + \mathrm{Cl}$ an aqueous medium, the rate of reaction is given by:

                     $\frac{\mathrm{d}\left[{\mathrm{IO}}^{-}\right]}{\mathrm{dt}}= \mathrm{k} \frac{\left[{\mathrm{I}}^{-}\right] \left[{\mathrm{OCl}}^{-}\right]}{\left[\mathrm{OH}\right]}$

The overall order of reaction is

• -1

• 0

• 1

• 2

Identify (D) in the following reaction series:

${\mathrm{CH}}_3-\mathrm{CH}={\mathrm{CH}}_2\stackrel{\mathrm{conc} {\mathrm{H}}_2{\mathrm{SO}}_4}{\to } \mathrm{A} \underset{∆}{\overset{{\mathrm{H}}_2\mathrm{O}}{\to }} \mathrm{B} \stackrel{{\mathrm{PCl}}_5}{\to } \mathrm{C} \stackrel{ \mathrm{Alcoholic} \mathrm{KOH} }{\to } \mathrm{D}$

• ${\mathrm{CH}}_3-{\mathrm{CH}}_2-\mathrm{OH}$

• ${\mathrm{CH}}_3-\left(\mathrm{OH}\right)\mathrm{CH}-{\mathrm{CH}}_3$

• ${\mathrm{CH}}_3-\mathrm{CH}={\mathrm{CH}}_2$

• CH₃CH₂CH₂OH

28.

Phenol is bifunctional compound because

• It is acidic and contain -OH

• It reacts with Na to give phenoxide

• It reacts with both Na and Zn to give phenoxide and benzene respectively

• Both (a) and (c)

Which of the following has lowest boiling point?

• p -nitrophenol

• m -nitrophenol

• o-nitrophenol

• Phenol

An organic compound X is oxidised by using acidified K₂Cr₂O₇. The product obtained reacts with phenyl hydrazine, but does not answer silver mirror test. The possible structure of X is

• CH₃COCH₃

• (CH₃)₂CHOH

• CH₃CHO

• CH₃CH₂OH