In the reaction,

$8\mathrm{Al}+3{\mathrm{Fe}}_3{\mathrm{O}}_4 \to 4{\mathrm{Al}}_2{\mathrm{O}}_3 + 9\mathrm{Fe}$ the number of electrons transferred from the reductant to the oxidant is

• 8

• 16

• 4

• 24

The bond angles of ${\mathrm{NH}}_3 > {\mathrm{NH}}_4^{+} \mathrm{and} {\mathrm{NH}}_2^{-}$ are in the order

• ${\mathrm{NH}}_2^{-} > {\mathrm{NH}}_3 > {\mathrm{NH}}_4^{+}$

• ${\mathrm{NH}}_4^{+} >{\mathrm{NH}}_3 > {\mathrm{NH}}_2^{-}$

• ${\mathrm{NH}}_3>{\mathrm{NH}}_2^{-} >{\mathrm{NH}}_4^{+}$

• $\mathrm{NH} > {\mathrm{NH}}_4^{+} > {\mathrm{NH}}_2^{-}$

Peptisation involves

• precipitation of colloidal particles

• disintegration of colloidal aggregates

• evaporation of dispersion medium

• impact of molecules of the dispersion medium on the colloidal particles

Iodine is formed when potassium iodide reacts with a solution of

• ZnSO₄

• CuSO₄

• (NH₄)₂SO₄

• Na₂SO₄

Which of the following does not represent the correct order of the property indicated?

• Sc³⁺ > Cr³⁺ > Fe³⁺ >Mn³⁺ - ionic radii

• Sc < Ti < Cr < Mn - density

• Mn²⁺ >Ni²⁺ > Co²⁺ <Fe²⁺ - ionic radii

• FeO < CaO < MnO < CuO - basic nature

If the elevation in boiling point of a solution of 10 g of solute (mol. wt. = 100) in 100 g of water is $∆{\mathrm{T}}_{\mathrm{b}}$ the ebullioscopic constant of water is

• 10

• 100 T_b

• $∆{\mathrm{T}}_{\mathbf{b}}$

• $\frac{∆{\mathrm{T}}_{\mathrm{b}}}{10}$

In Langmuir's model of adsorption of a gas on a solid surface,

• the rate of dissociation of adsorbed molecules from the surface does not depend on the surface covered

• the adsorption at a single site on the surface may involve multiple molecules at the same time

• the mass of gas striking a given area of surface is proportional to the pressure of the gas

• the mass of gas striking a given area of surface is independent of the pressure of the gas

$$\begin{gathered} {\mathrm{MnO}}_4^{-} + 8{\mathrm{H}}^{-} + 5{\mathrm{e}}^{-} \to {\mathrm{Mn}}^{2+} + 4{\mathrm{H}}_2\mathrm{O}; \mathrm{E}° = 1.51\mathrm{V} \\ {\mathrm{MnO}}_2 + 4{\mathrm{H}}^{+} + 2{\mathrm{e}}^{-} \to {\mathrm{Mn}}^{2+} + 2{\mathrm{H}}_2\mathrm{O}; \mathrm{E}° = 1.23 \mathrm{V} \mathrm{E}{°}_{{\mathrm{MnO}}_4^{-}|{\mathrm{MnO}}_2} \mathrm{is} \end{gathered}$$

• 1.70 V

• 0.91 V

• 1.37 V

• 0.548 V

A metal has bee structure and the edge length of its unit cell is 3.04 $\stackrel{°}{\mathrm{A}}$. The volume of the unit cell in cm³ will be

• $1.6 \times {10}^{21} {\mathrm{cm}}^3$

• $2.81 \times {10}^{-23} {\mathrm{cm}}^3$

• $6.02 \times {10}^{-23} {\mathrm{cm}}^3$

• $6.6 \times {10}^{-24} {\mathrm{cm}}^3$

30.

Which of the following hydrogen bonds are strongest in vapour phase?

• HF..........HF

• HF..........HCl

• HCl..........HCl

• HF..........HI