21.

Nitrobenzene on reaction with conc. HNO₃/H₂SO₄ at 80-100°C forms which one of the following products?

• 1, 2-dinitrobenzene

• 1, 3-dinitrobenzene

• 1, 4-dinitrobenzene

• 1, 2, 4-trinitrobenzene

Some meta-directing substituents in aromatic substitution are given. Which one is most deactivating?

• $-\mathrm{C}\equiv \mathrm{N}$

• $-{\mathrm{SO}}_3\mathrm{H}$

• $-\mathrm{COOH}$

• $-{\mathrm{NO}}_2$

The radical  because it has

• 6p-orbitals and 6 unpaired electrons

• 7p-orbitals and 6 unpaired electrons

• 7p-orbitals and 7 unpaired electrons

• 6p-orbitals and 7 unpaired electrons

Which of the following compounds will not undergo Friedal-Craft's reaction easily?

• Cumene

• Xylene

• Nitrobenzene

• Toluene

What is the activation energy for a reaction if its rate doubles when the temperature is raised from 20°C to 35$°$C ? (R = 8.314 J mol^-1 K^-1).

• 342 kJ mol^-1

• 269 kJ mol^-1

• 34.7 kJ mol^-1

• 15.1 kJ mol^-1

A hydrogen gas electrode is made by dipping platinum wire in a solution of HCl of pH=10 and by passing hydrogen gas around the platinum wire at 1 atm pressure. The oxidation potential of electrode would be

• 0.059 V

• 0.59 V

• 0.118V

• 1.18V

A reaction having equal energies of activation for forward and reverse reactions has

• $∆$S = 0

• $∆$G = 0

• $∆$H = 0

• $∆$H = $∆$G = $∆$S = 0

At 25°C molar conductance of 0.1 molar aqueous solution of ammonium hydroxide is 9.54 ohm^-1cm² mol^-1 and at infinite dilution its molar conductance is 238 ohm^-1cm² mol^-1. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is

• 2.080%

• 20.800%

• 4.008%

• 40.800%

A button cell used in watches functions as following

$$\begin{gathered} \mathrm{Zn}\left(\mathrm{s}\right)\hspace{0.17em}+\hspace{0.17em}{\mathrm{Ag}}_2\mathrm{O}\left(\mathrm{s}\right)\hspace{0.17em}+\hspace{0.17em}{\mathrm{H}}_2\mathrm{O} \left(\mathrm{l}\right)\hspace{0.17em} \rightleftharpoons 2\mathrm{Ag}\left(\mathrm{s}\right)\hspace{0.17em}+{\mathrm{Zn}}^{2+}\left(\mathrm{aq}\right)\hspace{0.17em}+\hspace{0.17em}2{\mathrm{OH}}^{-}\left(\mathrm{aq}\right) \\ \mathrm{If}\hspace{0.17em}\mathrm{half}\hspace{0.17em}\mathrm{cell}\hspace{0.17em}\mathrm{potentials}\hspace{0.17em}\mathrm{are}\hspace{0.17em} \\ {\mathrm{Zn}}^{2+}\left(\mathrm{aq}\right)\hspace{0.17em}+\hspace{0.17em}2{\mathrm{e}}^{-} \to \mathrm{Zn}\hspace{0.17em}\left(\mathrm{s}\right); {\mathrm{E}}^{°} = -0.76 \mathrm{V} \\ {\mathrm{Ag}}_2\mathrm{O}\left(\mathrm{s}\right)\hspace{0.17em}+\hspace{0.17em}{\mathrm{H}}_2\mathrm{O} \left(\mathrm{l}\right)\hspace{0.17em}+ 2{\mathrm{e}}^{-}\to 2\mathrm{Ag}\left(\mathrm{s}\right)\hspace{0.17em}+\hspace{0.17em}2{\mathrm{OH}}^{-}\left(\mathrm{aq}\right), {\mathrm{E}}^{°} = 0.34 \mathrm{V} \\ \mathrm{The}\hspace{0.17em}\mathrm{cell}\hspace{0.17em}\mathrm{potential}\hspace{0.17em}\mathrm{will}\hspace{0.17em}\mathrm{be} \end{gathered}$$

• 1.10 V

• 0.42 V

• 0.84 V

• 1.34 V

The number of carbon atoms per unit cell of diamond unit cell is

• 4

• 8

• 6

• 1