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    JEE Mains Study Notes for Surface Chemistry: Adsorption, Colloids. Catalysis and Sample Questions

    Anam Shams Anam Shams
    Content Curator

    Surface Chemistry holds a weightage of 17.9% in JEE Main Chemistry Syllabus. Topics tested from surface chemistry in JEE Main are Thermodynamics of Adsorption, Emulsions and Colloids. Minimum of 1 question is asked from this section. The aspect combined with Chemical Kinetics holds a lot of weightage in JEE Advanced paper as well with at least 8 questions. Check JEE Main Chemistry Preparation Tips

    JEE Main 2020 January session had one question on surface chemistry in each shift so was the case in 2019. Before proceeding for the study notes, lets take a quick look in one of the questions asked in 2019:

    Aerosol is a kind of colloid in which:

    • Solid is dispersed in gas

    • Gas is dispersed in solid

    • Gas is dispersed in liquid

    • Liquid is dispersed in water

    Unable to solve the question, read further to get acquainted with surface chemistry aspects. 

    Also Check 


    What is Surface Chemistry?

    What is Surface Chemistry?

    Surface chemistry is defined as the detailed study of surfaces and interfaces. 

    There are two types of phenomena that can be commonly seen in this topic which is

    • ADSORPTION and ABSORPTION; let's take a look upon both of the phenomena 

    ADSORPTION: When any substance stays on the surface of the substance then it is known as adsorption. The species which is going to adsorb is known as adsorbent and the surface onto which it takes place is known as the adsorbate. For example, silica gels, clays are the most commonly seen substance that possess adsorption qualities. 

    There is a process known as desorption also which is known as the removal of the adsorbed substance from the surface of an element. 

    ABSORPTION: When the substance fully penetrates inside the surface is known as absorption. The most common example of it is soaking cloth in the water. The water then penetrates into the cloth piece and we can say that the absorption process is occurring there. 

    Example

    An example of solid sol is?

    1. Piant
    2. Gem Stones
    3. Butter
    4. Hair Cream

    Must Read

    Difference Between Adsorption and Absorption

    ABSORPTIONADSORPTION
    Substance penetrate fullyThe substance remains onto the surface only.
    It is an endothermic processIt is the exothermic process
    It occurs at a uniform rateThe rate goes from increasing to decreasing
    It is unaffected by the temperatureIt is affected by the temperature

    Practice with JEE Main Question Paper


    Types of adsorption

    Types of adsorption

    There are mainly two types of adsorption are there namely physisorption and chemisorption.

    Physical Adsorption

    It involves adsorption of gases on the solid surface via weak van der Waal’s forces.

    Characteristics: There is no specificity in case of physical adsorption.

    • Easily liquefiable gases are strongly adsorbed by the means of the physical process only.
    •  It can be reversible in nature.
    • More surface area can adsorb more adsorbents.
    • No activation energy is needed.

    Chemical Adsorption or Chemisorption

    When the gas molecules or atoms are held to the solid surface via chemical bonds, this type of adsorption is chemical adsorption or chemisorption.

    Characteristics of Chemical Adsorption: 

    • It is irreversible in nature.
    • Chemisorption increases with an increase in surface area.
    • Enthalpy of chemisorption is high due to the involvement of chemical bonds.
    • Activation energy is required to initialise the process.
    • The unimolecular layer is formed.

    Adsorption Isotherm

    Example

    Haemoglobin and gold sol are examples of: 

    1. positively and negatively charged sols 
    2. positively charged sols
    3. negatively charged sols
    4. negatively and positively charged sols

    Adsorption Isotherm

     It is the graphical representation of the amount of adsorbent adsorb on the surface/adsorbate in relation to the pressure and constant temperature. 

    x/m= k. p1/ n

    where (n > 1)

    x is the mass of the gas adsorbed, m is the mass of the adsorbent, p is the pressure, k and n are constants which depends on the nature of the adsorbent and the gas at a particular temperature. Taking the log of the above equation, the following equation will be observed

    log x/m = log k +1/n log p

    Then the graphical representation made accordingly to the equation mentioned above. 


    Application of Adsorption

    • The gas mask that is used during the coal mines is made on the adsorption principle.
    • Adsorption can be used to kill germs also, chemisorption can be used there.
    • It can be useful in separation the noble gases.
    • Silica gel is often used to absorb moisture is based on the principle of adsorption. 
    • The vacuum with high power work on the principle of adsorption. 

    Catalysis

    Catalysis

    It is the process occur when the potassium chlorate decomposes into the potassium chloride and oxygen at the temperature of about 650-870K, but by adding magnesium dioxide the rate of reaction becomes faster and no need of high temperature is required there then it is known as the catalysis process occur there. This process is generally useful by fastening up the chemical reaction and in the short duration of the time. 

    Important features of the catalysis process: 

    • Constant activity is required to make the process in continuation. 
    • The reactant in the process should possess a quality to adsorb on the surface of the substance.
    • The adsorption process should not occur in the faster rate as it can immobilise the catalyst used to make the process faster. 
    • Catalysts can be chosen selectively in the process. 
    • The different catalyst used in the same reaction can give a different product after the reaction. 
    • So the selection of catalyst can be selective and focus on the products that we want to obtain. 

    Enzyme Catalyst

    Enzyme Catalyst

    These are known as a biochemical catalyst which is complex and organic in nature and are obtained from plants and animals. For example Invertase; it converts sucrose into fructose and glucose. 

    Characteristics of enzyme catalyst:

    • They are very specific in nature.
    • The work specifically under optimum pH. 
    • Activators and inhibitors have their concerned effects in the enzyme catalyst reactions.
    • They are highly effective in a particular range of temperature. 

    Colloids

    Colloids

    This is known as the heterogeneous system in which one substance is dispersed due to the very fine nature of it, it can mix well in the dispersion medium. This process has two kinds of activities going on known as;

    • Aggregation
    • Sedimentation

    Properties of the colloidal solution:

    • They form large aggregates. The properties like vapour pressure, osmotic pressure are small as compared to the value shown by the true solution.
    • Tyndall effect: when the light scatters by colliding the particles is known as the Tyndall effect. 
    • Colour of the particle is decided by the wavelength dispersed by the particles present in the solution. 
    • The movements which are shown by the particles when they collide with each other is known as the Brownian motions. 
    • Colloidal particles carry some energy when they collide in the form of electrical energy. 

    Emulsions

    Example

    Among colloids cheese, milk and smoke, the correct combination of the dispersed phase and dispersion medium is:

    1. C: liquid in solid M: liquid in solid  S: solid in gas
    2. C: liquid in solid M: liquid in liquid S: solid in gas
    3. C: solid in liquid M: liquid in liquid S: gas in solid
    4. C; solid in liquid M: solid in liquid S: solid in gas

    Ans: 

    Emulsions

    Two liquids colloidal systems form an emulsion. These are of two types:

    • Oil in water: When water acts as the dispersion medium. Like milk in vanishing cream.
    • Water in oil: When oil acts as a dispersion medium. Like butter and cream. 

    Hence, these above-mentioned notes will give the basic idea about the surface chemistry topic and helps a student preparing for IIT exam to strengthen his/her base. 


    Tips to Study JEE Main Chemistry

    Chemistry is a mixed subject, which means it contains both theoretical and practical based problems. Thus in order to achieve good marks, a student needs to practice upon both the skills. Students must take a look at some points before preparing for the exam which are:

    • A student must go through the detailed syllabus and work on the harder topics first then step by step they should go towards the easier ones. 
    • Detailed and topic wise elaborated notes are very necessary to make in order to build deep knowledge for the subject and to crack such a high-level examination.
    • A student must possess the time management skills as there is a lot of syllabi which a student must go through. 
    • A student must find a person who can take his tough doubts and become the support system during preparation and this would also avoid the mental burden which can be seen normally in the students who are preparing for the national level examination. 

    JEE Main Chemistry 30 Day Revision Plan

    WeekActivity 
    Week 1 (June 16 to 22)Physical Chemistry bears the most weightage in JEE Main Chemistry. High-weightage chapters from this area such as Electrochemistry, Atomic Structure, and Equilibrium to be studied in the beginning. Then, study less important chapters like Surface Chemistry and Solid State. Pick two chapters each day and study all the essential concepts and reactions.
    Week 2 (June 23 to June 30, 2020)Study Organic Chemistry during this week. Allocate more time to chapters with high weightage such as Aromatic Compounds, Alcohol, Alkyl Halides, and Ether. Then, study chapters with lower weightage such as Biomolecules and Carbonyl Compounds. 
    Week 3 (July 1 to 4, 2020)Study Inorganic Chemistry for this week. Start by studying chapters with the highest weightage like p Block, s Block, and Chemical Bonding. Move on to study less important chapters such as Metallurgy and Qualitative Analysis.
    Week 4 (July 5 to July 10, 2020)Brush through your study notes, important concepts, and reactions. Answer previous year’s papers for enhanced practice. Pick out questions from the Chemistry section and attempt them as quickly as you can, preferably within 45 minutes to 1 hour.
    Week 5 (July 10 to 17, 2020)Attempt mock tests every day of this week. Revise important concepts and reactions from all the chapters. 
    JEE Main Exam Week (July 18 to 23, 2020)Read the analysis of ongoing JEE Main papers and compare your performance. Use JEE Main Rank Predictor to estimate your rank and desired college.

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