Section: IPLCO DAILY PRACTICE PAPER-SC

TOPIC: SURFACE CHEMISTRY

1. A gold sol contains 0.193 g of gold per dm3. The particles are spherical in shape with radius of 120

nm. How many particles are present in 10-14 m3 of the sol? What is the interfacial area of the gold

particles in 1m3 of the sol? The density of gold is 19.3 gcm-3.

2. A soap 17 35C H COONa solution becomes a colloidal sol at a concentration of 31.2 10 M . On the

average, 132.4 10 colloidal particles are present in 1 mm3. What is the average number of stearate

ions in one colloidal particle (micelle)?

3. One gram of a water-insoluble substance of density 0.8 g cm-3 is dispersed in 2 litre of water, leading

to the formation of a colloidal sol containing 1013 particles of spherical shape per mm3. Determine

the radius of the particle.

4. A gold sol contains 0.24 g of gold per litre. When 10-1 m2 sample was examined under an ultra

microscope, on an average, 12 particles could be counted. Calculate the particle sizes if these are

assumed to be spherical and the density of gold is 19.3 g cm-3.

5. A mercury sol has been prepared by dispersing 0.272 g of mercury in 2 L of solution, giving spherical

particles of radius 12 nm. What is the total surface are of Hg particles present in 1 cm3 of sol?

6. The radius of a water molecule, assuming a spherical shape, is approximately 1.40Å. Assume that

water molecules cluster around each metal ion in a solution such that the water molecules

essentially touch both the metal ion and each other. On this basis, and assuming that 4, 6, 8 and 12

are the only possible coordination numbers, find the maximum number of water molecules that can

hydrate each of the following ions

(A) 2+Mg 0.65Åradius (B) 3 0.50ÅAl (C) 1.48ÅRb (D) 2 1.13ÅSr

7. The coagulation of 100 mL of a colloidal solution of gold is completely prevented by adding 0.25 g of

starch to it before adding 10 mL of 10% NaCl solution. Find out the gold number of starch.

8. For the coagulation of 100 mL of arsenious sulphide solution. 5 mL of 1 M NaCl is required. What is

the coagulating power of NaCl?

9. The flocculation value of BaCl2 for negative silver iodide sol is 2.43. How many ml of 0.2 M BaCl2 will

be sufficient to start coagulation of 400 ml of sol?

10. Gold number of starch is 25. How much of it is required to prevent coagulation of 100 mL of gold sol

adding 10 mL of 10% NaCl solution?

11. The particles of a particular colloidal solution of arsenic trisulphide ( 2 3As S ) are negatively charged.

Which 0.0005 M solution of the following salts would be most effective in coagulating this colloidal

solution, KCl, 2MgCl , 3AlCl or 3 4Na PO ? Explain.

12. A sample of charcoal weighing 6 g was brought into contact with a gas contained in a vessel of one

litre capacity at 027 C . The pressure of the gas was found to fall from 700 to 400 mm of Hg. Calculate

the volume of the gas (reduced to STP) that is absorbed per gram of the absorbent under the

condition of the experiment (density of charcoal sample is 1.5 g 3cm ).

13. 1 gm of active charcoal is taken and its surface area is 2 23.01 10 /m gm . It absorbs 100ml of 0.5 M

3CH COOH in a single layer. After absorption, its molarity becomes 0.49M. Find the surface area of

the charcoal covered by one molecule of acetic acid.

14. The coagulation of 100 3cm of gold solution is completely prevented by addition of 0.25g of starch to

it before adding 10 ml of 10% NaCl solution. The gold number of starch is

a) 0.025 b) 0.25 c) 2.5 d) 25

15. For the coagulation of 100 mL of 2 3As S sol, 5 mL of 1 M NaCl is required. The flocculation value of

NaCl is

a) 50 b) 5 c) 47.6 d) None of these

16. Silver iodide is used for producing artificial rains because silver iodide

a) is easy to spray at high altitude b) is insoluble in water

c) Has crystal structure similar to ice d) is easy to synthesize

17. Gelatin protects

a) Gold sol b) 2 3As S sol c) 3( )Fe OH sol d) All of these

18. The gold numbers of four protective colloids O, P, Q and R are 0.005, 0.01, 0.1 and 0.5 respectively.

The decreasing order of their protective power is

a) R, Q, P, O b) O, P, Q, R c) R, Q, R, O d) Q, R, O, P

19. A sol has positively charged colloidal particles. Which of the following solutions is require in lowest

concentration for coagulation?

a) NaCl b) 4 6[ ( ) ]K Fe CN c) 2ZnCl d) 2 4Na SO

20. The protective power of lyophilic sol is

a) dependent on the size of colloidal particles

b) expressed in terms of gold number

c) expressed by x/m

d) directly proportional to the magnitude of charge on it.

21. Lyophilic sols are more stable than lyophobic sols because

a) The colloidal particles have positive charge.

b) The colloidal particles have negative charge.

c) The colloidal particles are solvated.

d) There are strong electrostatic repulsions between the negatively charged colloidal particles.

22. An arsenious sulphide solution carries a negative charge. The maximum precipitating power of this sol

is possessed by

a) 2 4K SO b) 2CaCl c) 3 4Na PO d) 3AlCl

23. A colloidal solution is subjected to an electrical field. The particles move towards anode. The

coagulation of same sol is studied using NaCl, 2BaCl and 3AlCl solutions. Their coagulating power

should be

a) 2 3NaCl BaCl AlCl b) 2 3BaCl AlCl NaCl

c) 3 2AlCl BaCl NaCl d) 2 3BaCl NaCl AlCl

24. Which one of the following is correctly matched?

a) Emulsion – Curd b) Foam – Mist

c) Aerosol – Smoke d) Solid sol – Cake

25. Peptisation is a process of

a) Precipitation of colloidal particles.

b) Purification of colloids.

c) dispersing precipitate into colloidal particles in the electric field.

d) movement of colloidal particles in the electric field.

Without your involvement you never succeed with your involvement you never fail.