Gold numbers of protective colloids $\mathrm{A}, \mathrm{B}, \mathrm{C}$ and D are $0.50,0.01,0.10$ and 0.005, respectively. The correct order of their protective powers is

JEE Main · 2008 · 27 Apr 2008 · Offline · Surface Chemistry

Gold numbers of protective colloids

A, B, C

and D are

0.50, 0.01, 0.10

and 0.005, respectively. The correct order of their protective powers is

(A)D $<$ A $<$ C $<$ B
(B)C $<$ B $<$ D $<$ A
(C)A $<$ C $<$ B $<$ D✓ Correct
(D)B $<$ D $<$ A $<$ C

Answer: (C)

Solution

The gold number is the smallest mass of protective colloid that just prevents a standard gold sol from coagulating, so a small gold number marks a strongly protective colloid. With gold numbers

A = 0.50

B = 0.01

C = 0.10

and

D = 0.005

, the protective power runs opposite to these figures:

D

is the most protective, then

B

, then

C

, with

A

the least. Written in increasing order of protective power this is

A < C < B < D

JEE Main · 2008 · 27 Apr 2008 · Offline · Single correct option

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