The electrical charge on a colloidal particle is observed by:

Ultramicroscope
Scattering
Brownian movement
Electrophoresis

Solution

The electrical change on a colloidal particle is observed by electrophoresis. Under electric field, charged particles move in a particular direction.

According to Langmuir adsorption isotherm, the amount of gas adsorbed at very high pressures

reaches a constant limiting value
goes on increasing with pressure
goes on decreasing with pressure
increases first and then decreases with pressure

Solution

According to Langmuir Adsorption isotherm the amount of gas adsorbed at very high pressure reaches a constant limiting volume.

When KClO₃ is heated, it decomposes into KCl + O₂. If some MnO₂ is added, the reaction goes much faster because

MnO₂ decomposes to give O₂
MnO₂ provides heat by reacting
better contact is provided by MnO₂
MnO₂ acts as a catalyst

Solution

\(2KClO_{3} \overset{MnO_{2}}{\rightarrow} 2KCl + 3O_{2}\)

Which one of the following is an example for multi molecular colloid?

Aqueous starch sol
Aqueous enzyme sol
Alcoholic polystyrenesol
Aqueous sol of sodium laurylsulphate

Solution

Multi molecular colloids consist of aggregates of atoms or small molecules. Sulphur sol is an example of multi molecular colloids.

Solution

At the high pressure, Langmuir adsorption isotherm takes the form

\(\frac{x}{m} = \frac{ap}{1+bp}\)
\(\frac{x}{m} = \frac{a}{b}\)
\(\frac{x}{m} = ap\)
\(\frac{m}{x} = \frac{b}{a} + \frac{1}{ap}\)

Solution

Langmuir adsorption isotherm, is
\(\frac{x}{m} = \frac{ap}{1+bp}\)

At high pressure, 1 + bp = bp
\(\frac{m}{x} = \frac{ap}{bp} = \frac{a}{b}\)

The rate of oxidation of oxalic acid by acidified KMnO₄ increases as the reaction progresses. It is an example of

promoter
catalytic poison
auto catalysis
inhibitor

Solution

Which is correct about physical adsorption?

High temperature and high pressure favour adsorption
High temperature and low pressure favour adsorption
Low temperature and high pressure favour adsorption
Low temperature and low pressure favour adsorption

Solution

Physical adsorption involves weak forces, physical in nature with small heat of adsorption. Thus low temperature and high pressure favours physical adsorption.

The disease kala azar is caused by

colloidal antimony
milk of magnesia
argyrols
colloidal gold

Solution

Colloidal antimony is used in curing kala-azar.

The density of gold is 19 g/cm³. If 1.9 × 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 mm³ of the sol will be :

1.9 × 10¹²
6.3 × 10¹⁴
6.3 × 10¹⁰
2.4 × 10⁶

Solution

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