Plus Two Chemistry Chapter Wise Previous Questions Chapter 5 Surface Chemistry is part of Kerala Plus Two Chemistry Chapter Wise Previous Year Questions and Answers. Here we have given Plus Two Chemistry Chapter Wise Questions and Answers Chapter 5 Surface Chemistry.
Kerala Plus Two Chemistry Chapter Wise Previous Questions and Answers Chapter 5 Surface Chemistry
a. State Hardy-Schulze rule with the help I of example.
b. Why lyophilic colloids are used as protective colloids? [March-2018]
a. The rule states that the greater the valency of the coagulating power.
E.g., for the coagulation of a negative sol-like As2S3, the flocculating power of the coagulating ions is of the order: Al3+ > Ba2+ > Na+ Or, for a +ve sol-like ferric hydroxide, the flocculating power of the coagulating ions is of the order:
b. The lyophilic colloidal particles form a layer around lyophobic particles and thus protect them from electrolytes.
There are mainly two types of adsorption. They are physisorption and chemisorption.
a. Differentiate between physisorption and chemisorption.
b. Write any two applications of adsorption. [March-2017]
a. Physical adsorption (Physisorption):
- Force of attraction between adsorbate and adsorbent are van der Waals forces.
- Lacks specificity.
- Enthalpy of adsorption is low (20- 40kJmol-1)
- Occurs at low temperature.
Chemical adsorption (Chemisorption):
- Force of attraction between adsorbate and adsorbent are by chemical bonds.
- Highly specific.
- Enthalpy of adsorption is high (80-240kJ/mol).
- Occurs at high temperature,
- Production of high vacuum
- Gas masks
- Heterogeneous catalysis
- Froth floatation process
- Control of humidity
- Chromatographic analysis
i. Catalysis can be classified into two groups homogeneous and heterogeneous.
a. What do you mean by homogeneous catalysis?
b. Write one example for heterogeneous catalysis.
ii. Which of the following is an emulsifying agent?
a. Milk b. Butter
c. Gum d. Lampblack [March-2016]
i. a. The catalysis in which the reactant and the catalyst are in some phase is known as homogeneous catalysis.
The catalysis in which the reactant and the catalyst are in different phases is known as heterogeneous catalysis.
ii. c. Gum
i. Which of the following is lyophobic colloid?
a. starch in water
b. gum in water
c. soap in water
d. gold sol
ii. Write four applications of colloids. [March-2015]
i. d. gold sol
- In cottreli precipitator: Smoke particles get precipitated at the electrodes.
- In medicines: Most of the medicines are colloidal in nature as they are easily assimilated.
- In the rubber industry: Rubber latex is a colloidal solution of rubber particles.
- Cleansing action of soaps and detergents.
Adsorption is the phenomenon of higher concentration of particles on the surface than in the bulk of the solid.
i. For adsorption, ΔH = -ve. What is the sign of AS for adsorption?
ii. The dispersed phase and a dispersion medium in soap lather are respectively.
a. gas and liquid
b. liquid and gas
c. solid and gas
d. solid and liquid
iii. The formation of micelles takes place only above a particular temperature called ……………..
iv. The iron which is more effective for the coagulation of negative sol AS2S3 is? [Model-2014]
i. Entropy is the disarrangement of the molecule. When a gas adsorbed, the molecule gets arranged orderly, i.e., entropy decreases. Thus implies ΔS is negative.
ii. gas and liquid.
iii. Kraft temperature (Tk) or Critical micelle temperature
iv. Ba2 + in BaCI2
Sols are colloidal systems in which the dispersion medium is liquid and dispersed phase is solid.
a. Write any four differences between lyophilic sols and lyophobic sols.
b. Peptisation is a method of preparation of sols. Write a general procedure for peptisation. [March-2014]
|Lyophilic sols||Lyophobic sols|
|Easy to prepare||Difficult to prepare|
|Particles are a suitable size||Particles are not a suitable size|
|More solvated||Less solvated|
|More stable||Less stable|
b. Peptisation is the process by which precipitate is converted to a colloidal molecule. A precipitate is added to an electrolyte containing common ions. These common ions get adsorbed on a colloidal molecule. Commons of similar change get repelled and keep maximum distance,
Eg., adding FeCI3 to Fe(OH)3.
a. The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed adsorption.
i. What is adsorption isotherm?
ii. Write the mathematical expression of Freundlich adsorption
b. Enzymes are known as biochemical! catalysts. Write any two important characteristics of enzyme catalysis, [March-2013]
i. The variation in the amount of gas adsorbed by the adsorbent with pressure at constant temperature is expressed using a curve called adsorption isotherm.
ii. I where x/m is the extend of adsorption, P is the pressure, K and n are constants which depend on the nature of the adsorbent and the gas at a particular temperature.
i. Most highly efficient: One molecule of an enzyme may transform one million molecules of the reactant per minute.
ii. Highly specific in nature: Each enzyme is specific for a given reaction.
a. What is the Tyndall effect?
b. State Hardy Schulze rule which deals with the coagulation of colloids by the addition of an electrolyte.
c. What is a protective colloid? [March-2012]
a. The phenomenon of scattering of light by colloidal particles when a beam of light is passed through it is called tyndall effect.
b. The rule states that oppositely charged ions are effective for coagulation. The coagulating power of electrolyte increses with an increase in charge on the ions used for coagulation,
c. When a lyophilic sol is added to the lyophobic sol, they protect the lyophobic sols from electrolytes by forming a layer around them. Lyophilic sols used for this purpose are called protective colloids,
a. What are colloids?
b. Write any four applications of colloids? [Say-2012]
a. A colloid is a heterogeneous system in which one substance is dispersed as very fine particles in another substance called dispersion medium.
i. In cottrell precipitator: Smoke par- tides get precipitated at the elec- trades.
ii. In medicines: Most of the medicines are colloidal in nature as they are easily assimilated.
iii. In the rubber industry: Rubber latex is a colloidal solution of rubber particles.
iv. Cleansing action of soaps and detergents.
a. What is the effect of temperature on physisorption and chemisorption?
b. In certain cases, physisorption transfers into chemisorption as tempera-ture is increased. Explain with an example.
c. Explain how colloids get coagulated on an addition of salts? [March-2011 ]
a. Physical adsorption decreases with increase in temperature and chemisorption first increases and then decreases with increase in temperature.
b. At 83 K, Nitrogen gas is physisorbed on an iron surface as N2 where as at 773 K and above, chemisorption of nitrogen takes place as N atoms.
c. When a salt is added to the colloidal solution, the colloids interact with ions of opposite charge and causes neutralisation. This leads to coagula-tion.
As2S3 sol particles are negatively charged.
a. What happens when the barium chloride solution is added to the above sol?
b. How do you account for the above process?
c. What is the effect of adding aluminium chloride instead of barium chloride? [Say-2011]
a. When barium chloride is added precipitation of the colloidal particles take place.
b. The colloidal particles can be precipitated by adding-ions of opposite charge. Here neutralisation takes place.
c. The precipitation takes place faster when aluminium chloride is used instead of BaCI2. This is in accordance with Hardy Schulz rule, which states that greater the valency of the flocculating ion greater is the rate of precipitation AI3+ > Ba2+.
In an attempt to prepare ferric hydroxide sol by adding a small amount of ferric chlo-ride to water, one person got a precipitate of ferric hydroxide.
a. How can you help him to convert FeCI3 to Fe(OH)3 sol?
b. Name the phenomenon behind this.
c. What happens when BaCI2 is added to Fe(OH)3 sol?
d. Give a reason for the above. [June-2010]
a. A small quantity of FeCI3 is added to freshly prepared precipitate of Fe(OH)3 to get Fe(OH)3 sol.
b. The process is called peptization.
c. It gets coagulated.
d. When positively charged Fe(OH)3 is mixed with negatively charged BaCI2 mutual coagulation takes place.
a. Name the property of colloid involved in the construction of ultramicroscope.
b. Explain the above property.
c. What are the conditions to be satisfied to exhibit a Tyndall effect? [March-2010]
a. Tyndall effect.
b. The phenomenon of scattering of light by colloidal particles when a beam of light is passed through it is called tyndall effect.
i. The size of the colloidal particles and the wavelength of the light used should be comparable,
ii. There should be a very large difference between the dispersed phase and dispersion medium.
Whar is demulsification? Name two demulsifiers. [Model-2010]
The separation of an emulsion into its con-stituent liquids is called demulsification. This can be done by heating, freezing, cen-trifuging etc. Dehydrating agents and elec- trolytes which can destroy the charge on the dispersed phase are effective
What is adsorbate? Give an example. [Model-2009]
The substance which is adsorbed on the surface of another substance is called adsorbate.
Eg., O2, H2
We hope the Kerala Plus Two Chemistry Chapter Wise Questions and Answers Chapter 5 Surface Chemistry help you. If you have any query regarding Kerala Plus Two Chemistry Chapter Wise Questions and Answers Chapter 5 Surface Chemistry, drop a comment below and we will get back to you at the earliest.