In adding 1 mL of solution of 10 % NaCl to 10 mL of gold solution in the presence of 0.25 g of starch, the coagulation is just prevented. Starch has a gold number equal to:

1. 0.25                     

2. 2.5

3. 250                     

4. 0.025

What is a solution that isn't a lyophilic colloid?

1. Milk

2. Gum

3. Fog

4. Blood

The surface tension of lyophilic sols is:

1. Lower than H₂O

2. More than H₂O

3. Equal to H₂O

4. None of the above.

Brownian movement is caused by:

1. Colloidal solution.

2. True solution.

3. Suspension having size <1000 m$\mathrm{\mu }$.

4. All of the above.

What does the name "aquadag" refer to?

1. Cu in water sol.

2. Pt in water sol.

3. Graphite in water sol.

4. None of the above.

What results are obtained from adding FeCl₃ to K₄[Fe(CN)₆] in a diluted, cold solution?

1. Prussian blue sol.                     

2. Fe₄[Fe(CN)₆]₃ sol.

3. Positive sol.                               

4. All of the above.

Which of the following electrolytes, Na₂SO₄, CaCl₂, Al₂(SO₄)₃, and NH₄Cl, is the most effective coagulating agent for Sb₂S₃ sol?

1. Na₂SO₄                             

2. CaCl₂

3. Al₂(SO₄)₃                           

4. NH₄Cl

Among the given options, which element is the minimum required for precipitation of a negatively charged suspension of clay in water?

1. Aluminium chloride.

2. Potassium sulphate.

3. Sodium hydroxide.

4. Hydrochloric acid.

What is a colloidal solution that is commonly used to treat skin diseases?

1. Colloidal sulphur.                   

2. Colloidal silver.

3. Colloidal gold.                         

4. Colloidal antimony.

How is the flocculation value expressed?

1. Millimole per litre.

2. Mole per litre.

3. Gram per litre.

4. Mole per millilitre.