Surface Chemistry Test - 10

Correct answer is option A
During the adsorption of krypton on activated charcoal at low temperature.
ΔH <0 and ΔS <0.
Since adsorption is an exothermic process, the enthalpy change is negative. Heat is given out during the process.
The krypton gas adsorbed on activated charcoal is more ordered than unadsorbed krypton gas. Hence, the process occurs with a decrease in entropy. 
In other words, the entropy change is negative for the process.

The correct answer is option A
 
A colloid is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance called dispersion medium.
The essential difference between a solution and a colloid is that of particle size. While in a solution, the constituent particles are ions or small molecules, in a colloid, the dispersed phase may consist of particles of a single macromolecule (such as protein or synthetic polymer) or an aggregate of many atoms, ions or molecules. 
Colloidal particles are larger than simple molecules but small enough to remain suspended. Their range of diameters is between 1 and 1000 nm
 

The correct answer is Option D.
Hydrophilic colloid:- The colloid particles are attracted towards water. They have high viscosity due to strong attraction between the dispersed phase and water.
Hydrophobic colloid: The colloid particles are repelled by water.
They are called irreversible sols. Hydrophobic sols are often formed when a solid crystallizes rapidly from a chemical reaction or a supersaturated solution. When crystallization occurs rapidly, many centers of crystallization (called nuclei) form at the same time. Ions are attracted to these nuclei and very small crystals form. These charged crystals repel one another, so aggregation to larger particles is prevented.
They have a lack of attraction between the dispersed phase and water.
 

Gold number is the number of milligram of the protective colloid which prevent the coagulation  of 10 ml of red gold sol when 1 ml of a 10 percent solution of sodium chloride is added to it.

Here, Gold number of Hb  =0.03.

So weight of Hb require for 10 ml of gold is 0.03 mg.

So weight require for 100 ml of gold solution is 0.30mg.

The correct answer is option A

Smaller the size and lesser the viscosity, the faster the motion. Brownian movement arises because of the impact of the molecules of the dispersion medium with the colloidal particles.
 
As the size of the particle increases, the effect of the impacts average out and the Brownian movement becomes slow. Ultimately, when the dispersed particle becomes big enough to acquire the dimensions of suspension, no Brownian movement is observed.

It is because of more surface area of colloidal Pd

The Tyndall effect is seen due to light scattering by particles in a colloid or particles in a fine suspension. So, solution particles show the Tyndall effect due to the scattering of light and scattering is directly proportional to the size of sol particles.
 
Also, colloidal particles have a high molar mass so, their mole fraction is very less causing low colligative properties and hence, all colloidal dispersion give very low osmotic pressure and show very small freezing point depression or boiling point elevation.
 

The correct answer is option B
 
Reason for statement 1 will be the movement is due to the uneven bombardment of the colloidal particles in the dispersion medium.
Statement-1 is True, Statement-2 is True; Statement-2 is NOT a  correct explanation for Statement-1.

The correct answer is option A
Greater the valency of flocculating ions added, the greater its power to cause precipitation.
According to Hardy-Schulz rule, the coagulation (flocculating) value is inversely proportional to the charge on effective ions.
Hence, smaller the value, larger the power of an ion.

At isoelectric point, colloid particles will not move towards either of electrodse because they will come chargeless .