SURFACE CHEMISTRY

cooloidal solutions are not classified on the basis of:

• molecular size

• nature of the particles

• surface tension value

• interaction between dispersed phase and dispersion medium

The minimum amount of an electrolyte required to cause coagulation of a sol is called:

• coagulation value

• Gold number

• Protective value

• None of these

At what pH range the rate of enzyme catalysed reaction is maximum?

• 5 to 7

• 6 to 8

• 7 to 9

• 8 to 9

Hardy-Schulze law states that:

• solution must have higher gold number

• disperse phase and dispersion medium must be of the same sign

• micelles coagulate in presence of surfactants

• the ions carrying more opposite charge to that of sol particle are effective in coagulation

Blue colour of the sky is due to:

• absorption of light by dust particles

• reflection of light by dust particles

• scattering of light by dust particles

• presence of clouds

The gold numbers of protective colloids A, B, C and D are 0.04, 0.004, 10 and 40 respectively. The protective powers of A, B, C, D are in the order:

• A>B>C>D

• B>A>C>D

• D>C>A>B

• D>C>B>A

• A

• B

• C

• D

• I<II<III<IV

• I=III<II<IV

• II<IV<I<II

• II<III<IV<I

Answer explanation

Charge is directly proportional to coagulation power

• a

• d

• c

• b

• a

• b

• c

• d

Answer explanation

Fe(OH)₃ is a positive colloidal sol so for coagulation most effective ion is [Fe(CN)₆]^-4