Chemistry 1 Marks Question

Foam ; e.g. froth, whipped cream, soap lather.

Dispersed phase: liquid, Dispersion medium: liquid/ liquid fat dispersed in water.

Like charged particles cause repulsion/Brownian movement/solvation.

Sol : example- paints, cell fluids

In adsorption there is development of inter particle attractions between adsorbate & adsorbent.

Gel e.g. cheese, butter, jellies.

It first increases then decreases or graphical representation.

Chemisorption.

The catalytic reaction in which the pore structure of the catalyst and the size of the reactant and product molecules are comparable.

The process of settling of colloidal particles is called coagulation.

Chemisorption.

To make the surface available again for more reaction to occur/To remove the product formed from the surface of the catalyst.

Like Charged particles cause repulsion/Brownian motion/solvation.

Sol – paint, cell fluids.
Gel – cheese, butter, jellies.

Both are surface phenomenon/ both increase with increase in surface area.

The movement of colloidal particles under an applied electric potential towards oppositely charged electrodes is called electrophoresis.

Emulsions are liquid-liquid colloidal systems.

The scattering of light by colloidal particles is called “Tyndall effect”.

Due to unbalanced bombardment of the colloidal particles by the molecules of the dispersion medium.

• Emulsion: It is a colloidal mixture in which both the dispersed phase and the dispersion medium are liquids. The two or more liquids present in the mixture are generally immiscible in nature.

Example: Milk.

• Gel: It is a colloid in which the dispersed phase i.e. liquid has combined with the dispersion medium i.e. solid to produce a semisolid material.

Example: jellies.

Due to formation of n-type semiconductor providing free electrons.

Some medicines are more effective in colloidal form because medicine in colloidal form is easily absorbed by the body tissues.
For example: Antibiotics like streptomycin in the form of the colloidal sol is injected into the body for the more effective result.

When a beam of light is passed through a colloidal solution, then scattering of light is observed. This is known as the Tyndall effect. This scattering of light illuminates the path of the beam in the colloidal solution.

Dialysis is based on the principle that ions can pass through semipermeable membrane whereas colloidal particles cannot pass through it.

If the adsorbate is held on an adsorbent surface by weak van der Waal's forces, the adsorption is called physical adsorption.

Colloids can be classified on various bases:
On the basis of the physical state of the components (by components we mean the dispersed phase and dispersion medium). Depending on whether the components are solids, liquids, or gases, we can have eight types of colloids.

Zeolites are alumino-silicates that are micro-porous in nature. Zeolites have a honeycomb-like structure, which makes them shape-selective catalysts. They have an extended 3D-network of silicates in which some silicon atoms are replaced by aluminium atoms, giving them an Al−O−Si framework. The reactions taking place in zeolites are very sensitive to the pores and cavity size of the zeolites. Zeolites are commonly used in the petrochemical industry.

Catalysts provide an alternate path involving lower activation energy for the reactants.

Medicines are more effective in the colloidal form because of large surface area and are easily assimilated in this form.

The process of removing a dissolved substance from a colloidal solution by the means of diffusion through a membrane is known as dialysis. This process is based on the principle that ions and small molecules can pass through animal membranes unlike colloidal particles.

1. Chemisorption is highly specific in nature. It occurs only if there is a possibility of chemical bonding between the adsorbent and the adsorbate.
2. Like physisorption, chemisorption also increases with an increase in the surface area of the adsorbent.

When a beam of light is allowed to pass through a colloidal solution, it becomes visible like a column of light. This is known as the Tyndall effect. This phenomenon takes place as particles of colloidal dimensions scatter light in all directions.

This can be done:

1. By adding an electrolyte.
2. By adding a suitable solvent.

Blood is a colloidal solution when we rub moist alum on that part it causes coagulation which stops bleeding.

A colloidal solution having alcohol as the dispersion medium and a solid substance as the dispersed phase is called an alcosol.
For example: colloidal sol of cellulose nitrate in ethyl alcohol is an alcosol.

Colloidal system in which solid is dispersed in liquid is called sol and that in which liquid is dispersed in solid is called gel.

Clouds are colloidal in nature and carry charge. Spray of silver iodide, an electrolyte, results in coagulation leading to rain.

Colloids can be classified on various bases:
On the basis of the dispersion medium, sols can be divided as:

Dispersion medium	Name of sol
Water	Aquasol or hydrosol
Alcohol	Alcohol
Benzene	Benzosol
Gases	Aerosol

A colloidal solution is a state in which the particle size lies between 1nm and 1000nm. It appears to be homogeneous but actually it is heterogeneous.

The colloidal particles are charged and carry either a positive or negative charge. The dispersion medium carries an equal and opposite charge. This makes the whole system neutral. Under the influence of an electric current, the colloidal particles move towards the oppositely charged electrode. When they come in contact with the electrode, they lose their charge and coagulate.

Ne has higher critical temperature, i.e., stronger van der Waals forces therefore easily adsorbed.

1. Sols are dispersions of solids in liquids while emulsions are dispersions of liquids in liquids.
2. Sols are quite stable whereas emulsions are less stable.

All the particles in a colloidal sol carry the same charge and hence keep on repelling each other and cannot aggregate together to form bigger particles.

Colloidal solutions exhibit Tyndall effect because the size of the colloidal particles (1nm–1000nm) is such that they can scatter light.

If the adsorbate is held on the surface of the adsorbent as a result of chemical reaction forming surface compounds, it is called chemical adsorption.

Emulsions can be diluted to any extent on adding dispersion medium. The dispersed phase forms a separate layer if added in excess.

ZSM–5 (Zeolite Sieve with molecular porosity 5).

Smoke is passed through charged plates so that unburnt charged carbon particles get settled between the charged plate leaving behind air free from pollutants.

Kraft temperature is the minimum temperature above which the formation of micelles takes place.

It is a process by which colloidal solutions containing ionic impurities are purified. The colloidal solution containing ionic impurities is placed in a bag of parchment paper in distilled water in electric field. The ions come out through parchment paper and the sol is purified.

Aquasol and solid aerosol both have solid as the dispersed phase. They differ in dispersion medium. Aquasols have water as the dispersion medium while aerosols have gas as the dispersion medium.

It is important to remove CO in the synthesis of ammonia as CO adversely affects the activity of the iron catalyst, used in Haber’s process.

Higher is the critical temperature of a gas, greater is the ease of liquefication, i.e., greater are the van der Waal's forces of attraction and hence greater is the adsorption.

In this process, colloidal solutions are purified by carrying out filtration through special types of graded filters called ultra-filters. Filter paper allows the passage of electrolyte but does not allow the passage of colloidal particles.

A colloidal solution having water as the dispersion medium and a solid as the dispersed phase is called a hydrosol.
For example: starch sol or gold sol.

A colloidal solution having a gas as the dispersion medium and a solid as the dispersed phase is called an aerosol.
For example: fog.

It is a 4% solution of nitrocellulose in a mixture of alcohol and ether.

Sorption is the process in which adsorption and absorption take place simultaneously, e.g., dyeing of cotton fibres by azo dyes.

Rough surface of a catalyst provides more surface area for adsorption.

White precipitate of silver chloride becomes coloured due to adsorption of pigments of eosin dye.

The movement of colloidal particles under the influence of an applied electric field is known as electrophoresis. Positively charged particles move to the cathode, while negatively charged particles move towards the anode. As the particles reach oppositely charged electrodes, they become neutral and get coagulated.

Electrophoresis is due to charge on colloidal particles, the charged particles move towards one of the electrodes in electric field.

The adsorption of gases on the surface of metals is called occlusion.

Colloids can be classified on various bases:
On the basis of the nature of the interaction between the dispersed phase and dispersion medium, the colloids can be classified as lyophilic (solvent attracting) and lyophobic (solvent repelling).

Adsorption is surface phenomenon therefore adsorption is directly proportional to the surface area.
Finely divided substance has greater surface area. Greater is the surface area of the adsorbent, greater would be its absorbent power. That is why a finely divided surface is more effective as an absorbent.

A catalytic reaction which depends upon the pore structure of the catalyst and on the size of the reactant and the product molecules is called shape-selective catalysis. For example, catalysis by zeolites is a shape-selective catalysis. The pore size present in the zeolites ranges from 260-740pm. Thus, molecules having a pore size more than this cannot enter the zeolite and undergo the reaction.

Ice-cream is an emulsion. Gelatin is emulsifying agent which is used to stabilize the emulsion so it is added to ice-creams.

The process of settling down of colloidal particles i.e., conversion of a colloid into a precipitate is called coagulation.

Common salt (a typical crystalloid in an aqueous medium) behaves as a colloid in a benzene medium. Hence, we can say that a colloidal substance does not represent a separate class of substances. When the size of the solute particle lies between 1 nm and 1000 nm, it behaves as a colloid.
Hence, we can say that colloid is not a substance but a state of the substance which is dependent on the size of the particle. A colloidal state is intermediate between a true solution and a suspension.

Powderded substance are more effective adsorbent than their crystalline forms because when a substance is powdered its surface area increase and physisorption is directly proportional to the surface area of adsorbent

Gelatin stabilises the colloidal solution of gold. Gold sol is lyophobic sol or solvent repelling sol.