Colloidal solution of gold is in different colours like red, purple, blue and golden because of

• variable oxidation states of gold

• size difference in the particles of gold

• presence of impurities

• difference in the concentration of gold particles

The size of colloidal particles is in between

• 10^-7 - 10^-9 cm

• 10^-9 - 10^-11 cm

• 10^-5 - 10^-7 cm

• 10^-2 - 10^-3 cm

The stability of lyophilic colloids is due to which of the following?

• Charge on their particles

• Large size of their particles

• Smaller size of their particles

• A layer of medium of dispersion on their particles

Milk is

• fat dispersed in water

• water dispersed in fat

• water dispersed in oil

• fat dispersed in fat

In chemical adsorption, how many layers are adsorbed?

• One

• Two

• Multi

• Zero

What is the role of a catalyst in a catalysed reaction?

• Lowers the activation energy

• Increases the activation energy

• Affects the free energy change

• Affects the enthalpy change

For coagulating As₂S₃ colloidal solution which of the following will have the lowest coagulation value?

• NaCl

• KCl

• BaCl₂

• AlCl₃

Which of the following chemical reactions is homogeneous catalytic reaction?

• N₂(g) + 3H₂(g) $\stackrel{\mathrm{Fe}}{\to }$ 2NH₃(g)

• 2SO₂(g) + O₂(g) $\stackrel{\mathrm{NO}}{\to }$ 2SO₃ (g)

• CO(g) + 3H₂(g) _{$\stackrel{\mathrm{Ni}}{\to }$} CH₄(g) + H₂O (g)

• 2SO₂(g) + O₂(g) $\stackrel{{\mathrm{V}}_2{\mathrm{O}}_5}{\to } 2{\mathrm{SO}}_3\left(\mathrm{g}\right)$

69.

According to the adsorption theory of catalysis the speed of the reaction increase because

• the concentration of reactant molecules at the active centres of the catalyst becomes high due to adsorption

• in the process of adsorption, the activation energy of the molecules becomes large

• absorption produces heat which increases the speed of the reaction

• adsorption lowers the activation energy of the reaction

Which of the following will have the highest coagulating power for As₂S₃ colloid?

• PO${}_4^{3-}$

• SO${}_4^{2-}$

• Al³⁺

• Na⁺