Electrical Properties of Colloids

Q. Lyophilic colloidal sols are much more stable than lyophobic colloidal sols. This is due to the extensive solvation of lyophilic colloidal sols, which form a protective layer outside it which prevents it from forming associated colloids. Lyophilic colloidal sols also protect lyophobic colloidal sols from precipitation by the action of electrolytes. This is due to the formation of a protective layer by the lyophilic sols outside lyophobic sols. Lyophilic sols are also called protective sols.
Gelatin (lyophilic) protects gold sol (lyophobic) from coagulation on the addition of a solution of sodium chloride. The protective powers of different colloidal sols are measured in terms of gold number.
Gold number is defined as the amount of protective sol in milligrams that prevents the coagulation of 10 mL of a given gold sol on adding 1 mL of a $10\%$ solution of sodium chloride. Thus, the smaller the gold number of a lyophilic sol, the greater is the protective power.

The coagulation of 100 mL of colloidal solution of gold is completely prevented by the addition of 0.25 g of a substance “$X$” to it before the addition of 1 mL of $10\%NaCl$ solution. The gold number of “$X$” is

1. 0.25
2. 25
3. 250
4. 2.5

Q. 1.25 gm of a solid dibasic acid is completely neutralized by 25 ml of 0.25 molar barium hydroxide solution. Molecular mass of the acid i

Q. Zeta potential ( or electrokinetic potential ) is the

1. potential required to bring about coagulation of a colloidal sol
2. potential required to give the particles a speed of 1 cm/ sec in the sol
3. potential difference between fixed charged layer and diffused layer having opposite charge
4. potential energy of colloidal particles

Q. How does terminal alkyne react with NaNH2 .what is the product formed

Q. The minimum concentration of an electrolyte required to cause coagulation is called its flocculation value

1. True
2. False

Q.

What happens when a strong beam of light is passed through a colloidal solution

Q. The origin of charge on colloidal solutions is due to:

1. Frictional rubbing
2. Electron capture during Bredig’s arc method
3. Selective adsorption of ion on their surface
4. Addition of protective colloids

Q. The coagulation of 200 ml of a colloidal solution of gold is completely prevented by adding 0.50 g of starch to it before adding 1 ml of 10% $NaCl$ solution. Calculate the gold number of starch

1. 2.5
2. 25
3. 0.25
4. 250

Q. Equal volumes of each of two sols of AgI, one obtained by adding $AgN{O}_3$ to slight excess of KI and the other obtained by adding KI to slight excess of $AgN{O}_3$, are mixed together. Then:

1. The two sols will stabilize each other
2. The sol particle will acquire more electric charge
3. The sols will coagulate each other mutually
4. A true solution will be obtained

Q. When a small amount of an electrolyte is added to a colloidal dispersion, the dispersed phase particles are surrounded by either the anions or the cations. This is because:

1. The colloidal particles tend to selectively adsorb either positively or negatively charged ions
2. The ions of the electrolyte remove protons from the dispersion medium
3. The ions of the electrolyte remove electrons from the dispersion medium
4. Of Hydrogen bonding

Q. 7. Hco3- and co3 2- can be separated by (a) phenolpthalein (b) mgcl2 solution (c) hgcl2 solution (d) kcl solution

Q. Reactions in Zeolite catalysts depend on -

1. Pores
2. Apertures
3. Size of cavities
4. All of these

Q.

A sol has positively charged colloidal particles. Which of the following solutions is required in lowest concentration for coagulation -

1. NaCl

2. $K_4\left[Fe\right(CN{)}_6]$

3. $ZnC{l}_2$

4. $N{a}_{2}S{O}_4$

Q. The coagulating power of electrolytes having ions $N{a}^{+},A{l}^{3+}$ and $B{a}^{2+}$ for arsenic aulphide sol increase in the order

1. $A{l}^{3+}<B{a}^{2+}<N{a}^{+}$
2. $N{a}^{+}<B{a}^{2+}<A{l}^{3+}$
3. $B{a}^{2+}<N{a}^{2+}<A{l}^{3+}$
4. $A{l}^{3+}<N{a}^{+}<B{a}^{2+}$

Q. 14. 1000g Al is to be deposited on the cathode using Al2O3 in the solvent Na3AlF6 by a current of 125A.If cathodic reaction is as given then the time required for the passage of current is

Q. Which property of collodial solution is independent of charge on the collodial particles?

1. Electro - osmosis
2. Tyndall effect
3. Coagulation
4. Electrophoresis

Q. Which of the following is used for the preparation of colloids?

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Q. A negatively charged suspension of clay in water is needed for precipitation of minimum amount of -

1. Aluminium chloride
2. Potassium sulphate
3. Sodium hydroxide
4. Hydrochloric acid

Q. For the coagulation of 50 ml of ferric hydroxide sol, 10 ml of 0.5 M KCl is required. What is the coagulation value of $KCl$?

1. 5
2. 10
3. 100
4. None of these

Q. The colloidal solutions are purified by _______

1. Filtration
2. Dialysis
3. Centrifugation
4. Osmosis

Q. Which of the following are true with respect to the colour of a colloid?

1. The colour depends on the wavelength of the light
2. The colour depends on both the size and nature of the dispersed particles
3. In a light source containing many different wavelengths, a colloid scatters lower wavelengths to a much greater extent than the higher wavelengths
4. The colour of a colloid depends on the manner in which the observer receives light. When viewed under transmitted light, it could appear one way and when viewed under reflected light, the colloid could appear in a different colour

Q. In which of the following tyndall effect is not observed?

1. Suspensions
2. Emulsions
3. Sugar solution
4. Gold sol