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Brownian Motion

The density o...

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The density of gold is 19 g/cm3. If 1.9 x 104 g of goldis dispersed in one litre of water to give a sol havingspherical gold particles of radius 10 nm, then the numberof gold particles per mm3 of the sol will be

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Q. The density of gold is

19 g / {c m}^{3}

1.9 \times 10^{- 4} g

of gold is dispersed in one litre of water to give a sol having spherical gold particles of radius 10 nm, then the number of gold particles per

{m m}^{3}

of the sol will be:

Q. The density of gold is

19 g / c m^{3} .

1.9 \times 10^{- 4} g

of gold is dispersed in

1 L

of water to give a sol having spherical gold particles of radius

10 n m

, the number of gold particles per

m m^{3}

of the sol will be ___

\times 10^{6}

.

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.

Gold number of hemoglobin is 0.03. Hence 100 mL of gold sol will require what amount of hemoglobin (in g) so that gold is not coagulated by 1 mL of

10 % N a C l

Q. Assertion :Gold sol prepared by reduction method is negatively charged. Reason: The negative charge is due to the adsorption of negatively charged

A u O_{2}^{-}

ions on dispersed phase particles.

Q. If gold number for a protective colloid is

0.08

then how many milligrams would be needed to protect

50 m l

of a standard gold sol from being coagulated on addition of

5 m l

10

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