Chemistry M.C.Q (1 Marks)

1. The chemical used in process of tanning is known as Tannin.
2. It contains negatively charged colloidal particles whereas leather contains positively charged colloidal particles.
3. When the leather is soaked in tannin, due to the difference in charges, mutual coagulation occurs.
4. This coagulation results in the hardening of the leather after tanning process.

A catalyst is a substance, which increases the rate of reaction without itself being consumed at the end of the reaction, and the phenomenon is called catalysis. There are some catalysts which decrease the rate of reaction and such catalysts are called negative catalyst. Obviously, the catalyst accelerating the rate will be positive catalyst. However, the term positive is seldom used and catalyst itself implies positive catalyst. Catalysts are generally foreign substances but sometimes one of the product formed may act as a catalyst and such a catalyst is called "auto catalyst" and the phenomenon is called auto catalysis.

Potassium salts of fatty acids, containing no free alkali, are called soft soaps.

Sol is a colloidal suspension when a solid is dispersed in a liquid.
An example of sol is a gel, blood, paint, etc.
A liquid is dispersed in a gas called aerosols.
A gas dispersed in liquid or solid called foam.

High temperature is not favourable for physical adsorption since it is an exothermic process.

Peptisation is the process of converting freshly prepared precipitate into colloid.

The emulsifying agent used in oil in water emulsion is protein. Milk is an example of oil in water emulsion. It consists of liquid fat dispersed in water. Milk proteins act as an emulsifying agent.

An emulsion is a colloid of two or more immiscible liquids where one liquid contains a dispersion of the other liquids. In other words, an emulsion is a special type of mixture made by combining two liquids that normally don't mix.
Oil and water mixtures are emulsions when shaken together. The oil will form drops and disperse throughout the water.

The contact process is the current method of producing sulfuric acid in the high concentrations needed for industrial processes. Platinum used to be the catalyst for this reaction. However, as it is susceptible to reacting.

A catalyst is a substance, which increases the rate of reaction without itself being consumed at the end of the reaction, and the phenomenon is called catalysis. There are some catalysts which decrease the rate of reaction and such catalysts are called negative catalyst. Obviously, the catalyst accelerating the rate will be positive catalyst. However, the term positive is seldom used and catalyst itself implies positive catalyst. Enzymes acts as catalyst for biological process and lower activation energy and it increases efficiency.

The process of formation or conversion of a precipitate into a colloidal solution is called peptisation.

Stabilizers are the substance that are added in lyophobic sols to increase their stability.
Examples of stabilizers are an ammonium salt and a citrate.

When the force of attraction existing between adsorbate and adsorbent are weak Vanderwaal forces of attraction, the process is called Physical Adsorption or Physisorption. When the force of attraction existing between adsorbate and adsorbent are chemical forces of attraction or chemical bond, the process is called Chemical Adsorption.

The charge on the sol particles is due to one or more reasons, Viz.,

1. Due to electron capture by sol particles during electro dispersion of metals.
2. Due to preferential adsorption of ions from solution and/or.
3. Due to formulation of electrical double layer.

Peptization is a process of passing of a precipitate into colloidal particles on adding suitable electrolyte. The electrolyte added is known as peptizing agent.
For example: A reddish brown colored colloidal solution is obtained by adding small quantity of ferric chloride solution to the freshly precipitated ferric hydroxide.

The rate of physisorption is inversely proportional to temperature. The rate of physisorption increases with the decrease in temperature as it is an exothermic process.

Physisorption is not specific to any gas since it involves van der Waals forces and no specific bonds are formed.

Peptization is the process responsible for the formation of stable dispersion of colloidal particles in dispersion medium. In other words it may be defined as a process of converting a precipitate into colloidal sol by shaking it with dispersion medium in the presence of small amount of electrolyte. The electrolyte used in this process is called as peptizing agent.

Platinum and Palladium adsorb hydrogen on its surface.Platinum and Palladium are nobel/ inert metals they do not react with hydrogen.

A molecule of soap has two dissimilar ends. At one end is the hydrocarbon chain, which is water repellent and the other end is carboxylate anion which is polar end.
When soap is dissolved in water, many molecules come together and from a group called micelle. These micelles are formed because their hydrocarbon chains come together and the polar ends are projected outward.
When a Cloth with a spot of oil is soaked into a soap solution, soap dissolves tiny oil droplets by the hydrophobic end in the middle of the micelle. Due to the outer polar ends, these micelles dissolve in water and are washed away. In this way cloth gets cleaned.

Substances, which are added to soaps change their properties in order to make them more useful for a particular application, are called fillers. Fillers make the soap harder, harsher on the skin and lower the cost.

The enthalpy change value of the reaction will not be affected by a catalyst. A catalyst will only lower the required activation energy for the reactions. Since it will lower the activation energy for both the forward and reverse reactions to the same extent, the net change in enthalpy is zero.

A germ pore is a small pore in the outer wall of fungal pore which is used for initiation of pollen tube.

It is a well known fact that the metal used as a catalyst in the hydrogenation of oil is nickel.

River water is a colloidal solution of clay. Sea water contains a number of electrolytes. When river water meets the sea water, the electrolytes present in sea water coagulate the colloidal solution of clay resulting in its deposition with the formation of delta.

The substances that stabilise emulsions are called emulsifiers. Agar, gum and soap all are emulsifier while milk is an emulsion, not an emulsifier.

When electrophoresis, i.e., movement of particles is prevented by some suitable means, it is observed that the dispersion medium begins to move in an electric field. This phenomenon is termed electro osmosis.

Soap lather is an example of foam. Dispersion medium is liquid and dispersed phase is gas.

In the figure adsorption of coloured particle from charcoal is shown. Solution of raw sugar is filtered by animal charcoal and yellowish brown colour of raw sugar is adsorbed and filterate is colourless which gives white colour on crystallization.

Detergents are better than soaps because they are less affected by hard water, as the hydrocarbon chains in detergents do not precipitate with calcium, magnesium and other metal ions.

Smoke precipitator works on the principle of neutralization of charge on colloids.
Smoke coming out of the chimneys contain a lot of unburnt carbon particle.
Smoke is the colloidal solution of the solid particles such as carbon, arsenic, dust particles etc. These particles are injurious to health and have to be precipitated.
Carbon particle is charged particles and can not be precipitated. Thus, a metal plate of an oppositely charged particle is used for their precipitation.
This is done by the Cottrell smoke precipitator which neutralizes the charge on the carbon particles and neutralizes them.
In this way, smoke coming out of the chimneys gets free from the charged particles.

Lyophobic sols are protected due to formation of film of lyophobic sol.

The emulsion is a colloidal system consisting of immiscible liquids. Milk is an example of emulsion in which particles of liquid fat are dispersed in water. In common occurrence, however, one of the liquids is water and the other, and oily substance insoluble in it. The suspended droplets are larger than the particles of the sols. It is because of the density differences between the phases being small.

In homogeneous catalysis, only, the reactant and product are in same phase and composition is uniform throughout.

Lyophilic colloids have a unique property of protecting lyophobic colloids. When a lyophilic sol is added to the lyophobic sol, the lyophilic particles form a layer around lyophobic particles and thus protect the latter from electrolytes. Lyophilic colloids used for this purpose are called protective colloids.

Aqueous solution of soap above critical micelle concentration leads to the formation of colloidal solution. Tyndall effect is a characteristic of colloidal solution in which colloidal particles show a coloured appearance when sunlight is passes through it and seen perpendicularly.

Colloidal sols have larger surface area which provides larger sites for reactions.So,they are more effective for medical purposes.

Presence of equal and similar charges on colloidal particles provides stability to colloids as repulsive forces between charge particles having same charge prevent them from colliding when they come closer to each other.

Collodion is a colloidal sol of cellulose nitrate in ethyl alcohol.

Soaking of water by a sponge is an example of physical adsorption.
Water molecules are held to the surface of the sponge by weak van der Waals forces.

Protein water is an example of colloidal sol in which the affinity of the sol particles for the medium is due to hydrogen bonding.

When used for cleaning, soap allows insoluble particles to become soluble in water and rinsed away. The insoluble fat molecules become associated inside micelles tiny spheres formed from soap molecules with polar hydrophilic groups on outside and lipophilic pocket which shields the fat molecule from the water making it soluble.

Micelle formation is possible only above critical micelle concentration and on dilution the micelles may form electrolytes.

Action of a catalyst is highly selective in nature, i.e., a given substance can act as a catalyst only in a particular reaction and not for all the reactions. It means that a substance which acts as a catalyst in one reaction may fail to catalyse another reaction. Catalyst does not change the enthalpy of reaction.

The adhering of the molecules of gas on the surface of a solid is called adsorption. It is a surface phenomenon. It is defined as the phenomenon of accumulation of higher concentration of one substance on the surface of another than in the bulk.

River water contains charged colloidal particles of clay, sand and many other materials. Sea water is very big store house of a variety of electrolytes dissolved in it. As soon as river water comes in contact with sea water coagulate the suspended colloidal particles which ultimately settle down at the point of contact. Thus the level of the river bed rises. As a result, water adopts a different course and delta is formed in due course of time.

Adsorption and absorption when take place together, it is known as sorption.

An emulsion is a liquid dispersed in either a liquid or solid.
Milk is an emulsion. It is an example of oil in water emulsion. It consists of particles of liquid fat dispersed in water.

As we know that like dissolved like, polar part dissolves in water, since water is a polar solvent.

Physical adsorption is appreciable at low temperature.
In physical adsorption, equilibrium is established between the adsorbate and the fluid phase. In solid or gas systems, at not too high
pressures, the extent of physical adsorption increases with increase in gas pressure and usually decreases with increasing temperature.
Since physical adsorption is an exothermic process, the rate of physical adsorption is inversely proportional to temperature.

In solid sol, dispersed phase is solid and dispersion medium is also solid. Pigmented plastics, coloured glasses are examples of solid sol.

In a reaction catalyst changes physically and qualitatively as it is unaltered during the reaction and remains quantitatively intact after completion of reaction, and does not change chemically.

Tyndall effect is the optical property shown by the colloidal particle. Above critical micelle concentration, a solution of soap behaves as associated colloid that is why it shows tyndall effect.

Peptization is a process in which colloidal solution is prepared by adding electrolyte to a precipitate. The electrolyte is added called as peptizing agent. This peptization process also called as deflocculation when the ferric chloride solution is added to the ferric hydroxide precipitate, it gives sol of ferric hydroxide. Therefore, we can say that in peptization, precipitate breaks and disperse into a colloidal solution.

Colloid acts as a transport vector of different contaminants in water surfaces. For example, heavy metals and radionucleides are absorbed on colloid surface and are carried throughout the water Enzymes, which are important biomolecules in human body, freely move about in the water because of colloid action. Colloids are used in intravenous therapy where they increase the intravascular volume and maintain a high colloid osmotic pressure in the blood.

Finely powered or colloidal catalyst particles having small surface area cannot be rich in free valencies. When the catalyst is finely powdered the surface area of the particle is small but total surface area is very large.

Adsorption: The phenomenon of attracting and retaining the molecules of a substance on the surface of a liquid or a solid resulting into a higher concentration of the molecules on the surface is called adsorption.
Adsorption of a gas by charcoal: Finely divided activated charcoal has a tendency to adsorb a number of gases like ammonia, sulphur dioxide, chlorine, phosgene, etc. In this case, charcoal acts as an adsorbent while gas molecules act as adsorbate.
Adsorption of oxalic acid on activated charcoal: The molecules of gases or liquids or the solutes in solutions get adhered to the surface of the solids. In adsorption process two substances are involved. One is the solid or the liquid on which adsorption occurs and it is called adsorbent. The second is the adsorbate, which is the gas or liquid or the solute from a solution which gets adsorbed on the surface.

Absorption implies that a substance is uniformly distributed, through the body of the solid or liquid.

When the reactant and catalyst are in different phase it is known as heterogeneous catalysis.

Adsorbate adsorbs impurities from surface of substance Animal charcoal is good adsorbate. The impurities adsorb on its surface and thus it decolourises colour of liquids.

Argyrol is a silver sol and is used as an eye lotion. Silver bromide, gelatin and glass plate are used in the making photographic plates.

On increasing temperature physisorption changes to chemisorption. As the temperature increases, energy of activation of adsorbate particles increases which leads to formation of chemical bond between adsorbate and adsorbent. Hence, physisorption transform into chemisorptions.

Bredig's arc method is a method of preparation of the colidal solution of metals such as silver, gold, platinum etc. Copper sol is not prepared using Bredig's arc method.

A catalyst is a substance, which increases the rate of reaction without itself being consumed at the end of the reaction, and the phenomenon is called catalysis. There are some catalysts which decrease the rate of reaction and such catalysts are called negative catalyst. Obviously, the catalyst accelerating the rate will be positive catalyst. However, the term positive is seldom used and catalyst itself implies positive catalyst. Catalysts are generally foreign substances but sometimes one of the product formed may act as a catalyst and such a catalyst is called "auto catalyst" and the phenomenon is called auto catalysis.

Adsorption of gas on the surface of solid is also known as occlusion.

Mayonnaise often abbreviated as mayo is a thick, creamy dressing often used as a condiment.
It is a stable emulsion of oil, egg yolk, and acid, either vinegar or lemon juice, with many options for embellishment with other herbs and spices. It is an emulsion.
Whereas Whipped cream is a colloid. It consists of a gas in a liquid, so it is foam, Fog is an example of liquid aerosol, Gelatin is a sol.

The process of separation of two liquids of an emulsion into separate layers is known as demulsification. It can be brought about by heating, centrifuging etc. For example, cream is separated from milk by centrifuging.

The colloidal dispersion of a liquid in a liquid is called emulsion.
In these systems, one liquid is dispersed in another liquid immiscible with it.
For example, milk is an emulsion of oil in water. The particles of liquid fat are dispersed in water.
Codliver oil is an emulsion of water in oil. consists of particles of water dispersed in oil.

A catalyst is a substance, which increases the rate of reaction without itself being consumed at the end of the reaction, and the phenomenon is called catalysis. There are some catalysts which decrease the rate of reaction and such catalysts are called negative catalyst. Obviously, the catalyst accelerating the rate will be positive catalyst. However, the term positive is seldom used and catalyst itself implies positive catalyst. Catalysts are generally foreign substances but sometimes one of the product formed may act as a catalyst and such a catalyst is called "auto catalyst" and the phenomenon is called auto catalysis.

Soaps do not create water pollution because they are biodegradable. Biodegradable are the substances that can be decomposed by bacteria and thereby avoiding pollution.

Hydrogen exists as gas where palladium is in element existing as solid.

Extent of adsorption of adsorbate from solution phase increases with increase in the amount of adsorbate in the solution. As amount of adsorbate in the solution increases interaction of adsorbent increases which leads to increase in extent of adsorption.

When a chalk stick is dipped in ink, the surface retains the colour of the ink due to adsorption of coloured molecules while the solvent of the ink goes deeper into the stick due to absorption.

Sorption is the term used when both adsorption and absorption takes place. The substance gets uniformly distributed in the bulk of the solid but at the same time its concentration is higher at the surface than in the bulk.