Question 2: Which of the following is not applicable to the phenomenon of adsorption? The reactant molecules are adsorbed on the surface of solid catalyst by physical adsorption or chemisorptions. In fact, it was in use by the Egyptians as early as 2,000 B.C. Also, cracks are easy generated at high temperature and are detrimental to the mechanical properties of the green body. Free PDF Download of CBSE Chemistry Multiple Choice Questions for Class 12 with Answers Chapter 5 Surface Chemistry. For z = 1, 2 and 3 the ratio of the CCCs are 1, 0.016 and 0.0014, respectively. a. The particle size of the mineral could be in the 38–150 μm range. By Persistent dialysis - On prolonged dialysis, traces of the electrolyte present in the sol are removed almost completely. When an electrolyte is added to the colloidal solution, the particles of the sol take up the ion which is oppositely charged and thus get neutralised. These solutions for class 12 chemistry chapter 5 pdf provided here has answers to the questions in the textbooks, NCERT exemplar problems, MCQ’S, short and long answer questions. These phenomena concerns several scientific disciplines. W.H. Free PDF Download of CBSE Chemistry Multiple Choice Questions for Class 12 with Answers Chapter 5 Surface Chemistry. Although the flocs formed tend to be distributed by convective mass transfer, their distribution is also influenced by the force of gravity. 1. NOM, particularly humic and fulvic acids, can react with chlorine, which is typically used to disinfect drinking water, to form chlorination by-products. The use of an efficient in-line flocculation strategy leads to compact treatment plant designs compared to conventional systems. Coagulation is an ancient technology [89]. • The final step is flocculation. The shrinkage rate decreases with increase in coagulation temperature which is similar to the effect observed in compressive strength. Time-delayed in situ generated Mg2+reacts with the dispersant, forming Mg-poly(acrylate), and shifting the adsorption equilibrium of the dispersant on the particles surface, with the consequent coagulation of the concentrated alumina suspension (Prabhakaran et al., 2008, 2010). Adsorption: In the same way, As(V) adsorbs on the coagulates through chemical adsorption. The impact of coagulation was particularly significant at coagulant doses >1 mg Fe/L. Both mechanisms accelerate the coagulation of the suspension at high temperature (70°C). It can be concluded that among all of the aforementioned technological processes, coagulation is a very common method and very important unit that often cannot be omitted or substituted. Surface Chemistry Class 12 Chemistry MCQs Pdf. Sanghyun Jeong, ... Saravanamuthu Vigneswaran, in Comprehensive Membrane Science and Engineering (Second Edition), 2017. Shaoxian Song, Marisol Gallegos-Garcia, in The Role of Colloidal Systems in Environmental Protection, 2014. Electrolytic coagulation could be enhanced by adjusting pH and electrolyte concentration and by optimizing coagulation kinetics (Hiemenz and Rajagopalan, 1997). While, in flocculation various polymers are used to make bridges between the flocs which bind large clumps or agglomerates of the colloids. Wilkinson *, J.-C. N~gre, J. Buffie CABE, Sciences II University of Geneva, 30 Quai Ernest Ansermet, 1211 Geneva 4, Switzerland Received 15 March 1996; accepted 15 August 1996 Abstract Organic matter … The result shows that enhanced coagulation is the most practicable technology for eliminating DBPs compared with the other complicated and expensive equipment modifications. Tyndall effect is not exhibited by true solutions. Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot.It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair.The mechanism of coagulation involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin. The colloid stability of hydrous oxides may be affected by electrolytes in a different way than that of hydrophobic colloids. Desorption:-Removal of. Well, according to the general definition, coagulation is one of the various properties exhibited by colloidal solutions. Coagulation is especially useful in removing the chemical phosphorus from water. Coagulation of lyophobic sols can be done by the following methods: Example- A negatively charged ion when added to a positively charged sol causescoagulation. The method was applied to process alumina, zirconia (YSZ), silica and alumina-silica composites with calcium iodate, calcium citrate and calcium phosphate as the most common reagents to the release of Ca2+ ion. This is done by, Al3+> Ba2+>Na+ is the order in terms of flocculating power, [Fe(CN)6] 4-> PO43->SO42->Cl- is the order in terms of flocculating power, Factors affecting adsorption of Gases by Solids. Coagulation or precipitation. In order to eliminate DBPs, USEPA, and AWWA proposed “enhanced coagulation” to remove the precursors of DBPs, that is, NOM. 1. Coagulation is a process of aggregating together the colloidal particles so as to change them into large sized particles which ultimately settle as a precipitate. There is enough surface-active organic matter to be adsorbed on the surface of the particles, thus keeping particles discrete. Subject: Chemistry, asked on 20/12/12 what is hardy schulze rule ? In water treatment, coagulation flocculation involves the addition of compounds that promote the clumping of fines into larger floc so that they can be more easily separated from the water. _____ Question 7: Explain the following . Coagulation is a process of aggregating together the colloidal particles so as to change them into large sized particles which ultimately settle as precipitate. The words "coagulation" and "flocculation" are often used interchangeably, but they refer to two distinct processes. In this case, they accumulate a surface charge and an electrical double layer forms around each particle. JOURNAL OF Contaminant Hydrology ELSEVIER Journal of Contaminant Hydrology 26 (1997) 229-243 Coagulation of colloidal material in surface waters: the role of natural organic matter K.J. Coagulation and flocculation are often considered as a pretreatment step in DAF processes. Generally, the flocs produced can be separated from water by settling, filtration, flotation, etc. Hence, they are used as electrodes for carrying out electrolysis. Besides the coagulation due to the increase of ionic strength, in some of the studies a thermally activated hydrolysis decomposition of an ester (Glycerol diacetate) was the other coagulation mechanism also to be present. Electrolytic Coagulation: This step is exactly the same as the common coagulation process mentioned above. The coagulation of alumina suspensions by the controlled release of Ca2+ from calcium citrate complex assisted by pH shift in the presence of glycerol diacetate has also been reported (Xu et al., 2016). Coagulation is caused by (i) Electrophoresis, (ii) Mutual precipitation by mixing oppositely charged sols in proper proportion. Coating: The small coagulates generated in the electrolytic coagulation step coat a coarse mineral on the surfaces, forming much larger coagulates that are a mixture of colloidal particles and coarse mineral particles. Coagulation of lyophobic sols can be carried out by (i) Electrophoresis: The colloidal particles get attracted towards oppositely charged electrodes, get discharged and coagulated. Processed bodies with homogeneous microstructure and good mechanical properties suggest that this colloidal method is promising to obtain ceramic-matrix composites with complex shapes, with uniform composition and high mechanical strength. Suspension: (i) It is heterogeneous. The branch of the Chemistry wich deals with the study of surface phenomena is called surface Chemistry. Adsorption The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed adsorption . Qing Chang, in Colloid and Interface Chemistry for Water Quality Control, 2016. In the tertiary treatment, we use many kinds of physical and chemical methods, including aeration, adsorption, coagulation, sedimentation, sand filtration, ion exchange, electrodialysis, and reverse osmosis to reach the high requirements. It is irreversible. It can also be called as precipitation. This process includes three or four steps, namely, electrolytic coagulation, adsorption, sedimentation, or filtration. Besides, with the increase in temperature the solubility of calcium iodate increases, releasing Ca2+ ions. Coagulation is generally brought about by the addition of electrolytes. Often, colloidal particles are suspended in water. Coagulation-flocculation is a chemical water treatment technique typically applied prior to sedimentation and filtration (e.g. Here you can get Class 12 Important Questions Chemistry based on NCERT Text book for Class XII.Chemistry Class 12 Important Questions are very helpful to score high marks in board exams. Refer to the figure on the right and review the following facts: Milk is an emulsion with fat particles (globules) dispersed in an aqueous (watery) environment. Answer: Coagulation: The process of converting a colloidal solution into precipitate is called coagulation. GDA hydrolysis reaction allows the decomposition of magnesium citrate, with the production of Mg2+. After the discovery of harmful disinfection by-products (DBPs) in chlorinated waters, the removal of organic DBP precursors gained priority in drinking water treatments, and the coagulation process is usually optimized/enhanced for the reduction of natural organic matter (NOM). (For color version of this figure, the reader is referred to the online version of this book.). Therefore, the coating could be realized through electrostatic attraction between the small negatively charged coagulates and the coarse positively charged mineral. This phenomenon is also referred to as coagulation or flocculation and such a suspension is also called unstable. Afterwards the addition of glycerol diacetate (GDA) induced the coagulation of alumina in the chelated suspension, at different temperatures (40–70°C). The fat globules do not coalesce and form a separate layer (oil off or churn) because they are protected by a … Get Answer to your question from 'Surface Chemistry' by Meritnation Experts with examples. The PCN coagulation mode resulted in a relatively narrow coagulation zone, which could limit the application of traditional aluminum coagulant under some circumstances. Liquid milk is converted into a solid mass. Finally, advances in the coagulation process in terms of prepolymerized, new, and natural organic coagulants are also reviewed. Peptization. Various parameters can be determined including partial thromboplastin time (PTT), prothrombin time (PT), thrombin time (TT), thrombin generation, fibrinogen, fibrinogen and fibrin degradation products (FDP), and specific coagulation factors. Lyophilic sols are stable because of charge and solvation of colloidal particles. During the process the aggregation of particles results in the shrinkage of the suspension and loss of water. The arsenate ion (As(V)) in the water would form ferric arsenate (FeAsO4) or aluminum arsenate (AlAsO4) with the Al3+ or Fe3+ ions and thus would adsorb on the coagulates through chemical adsorption. rapid sand filtration) to enhance the ability of a treatment process to remove particles. The negatively charged ion is called coagulating ion/flocculative ion as it neutralises the colloid to cause coagulation. In the early 1970s, the coagulation process was found to be efficient for removing As(V) from water (Gulledge and O'Connor, 1973). When (a) is reacted with sodium metal it gives compound (d), C 8 H 18 which is different from the compound formed when n-butyl bromide is reacted with sodium.Give the structural formula of (a) and … Coagulation is of great importance in the transport and distribution of suspended colloidal particles in natural waters. The interface or surface is represented by separating the bulk phases by a hyphen or a slash. DCC by pH shift to IEP is a reliable process to produce ceramic bodies, but the wet strength might be not high enough for their handling. Other processes where breakage is the essential mechanism are those related to size reduction of solids (e.g. For either method, preliminary testing of flocculants is highly recommended.53, Especially, coagulation substantially reduced fouling potential and compressibility of the AOM cake/gel layer. In some cases cooling the sol also results into its coagulation. The coarse particle enhancement of coagulation of fine particles not only strongly reduces particle numbers in suspensions, but also greatly increases coagulate size. The first-stage treatment (or primary treatment) consists of screening, gravity settling, and flotation, which are used consecutively to remove particles larger than 100 μm. In colloid chemistry, coagulation or electrolytic coagulation is defined as the aggregation of colloidal or fine particles in a medium through the addition of electrolytic ions. Also, some of the products of the coagulation system contribute to the innate immune system by increasing vascular permeability and acting as chemotactic agents for phagocytic cells. Coagulation is a process that makes finely divided particles aggregate and form large flocs, which can be settled and separated from water. Large shrinkage rates mean strong aggregation of particles and water is squeezed out of the sample which leads to high green density and contributes to high compressive strength. The study of surfaces or interface is known as Surface Chemistry. Coagulation and Organic Matter in Natural Water • Is a complex mixture of organic compounds • It results from the degradation of vegetative matter in the catchment or from surface affected groundwaters • Consists of compounds resulting from the growth and decomposition of algae and weeds within the surface water source itself This is due to the formation of less compressible and more porous cake former. They participate in many chemical processes in natural water and often occur as colloids in water. Multiple Choice Questions (Type-I) The colloidal particles in the water aggregate into coagulates in the presence of electrolytic ions (Al3+ or Fe3+) that are termed coagulants. ... 1000 mL of the sol require NaCl for complete coagulation = 50 millimoles. Among various types of coagulants iron salts such as ferric chloride and ferric sulfate are most successful for arsenic removal from water. Coagulation or Flocculation or Precipitation “The phenomenon of the precipitation of a colloidal solution by the addition of the excess of an electrolyte is called coagulation or flocculation.” The coagulation of the lyophobic sols can be carried out by following methods. In the heterogeneous catalysis, generally the reactant are the gases where as catalyst is a solid. (9) is the Schulze-Hardy rule, indicating that the minimum counter-ions concentration that will make the transition from a stabilized to coagulated slurry is inversely proportional to the sixth power of valence z. The major drawback of the coagulation/flocculation process is the large amount of sludge produced having substantial arsenic concentration [20]. It is specific. The stability of lyophilic sols is due to two factors : 1) Charged and The bubble size distribution in bubble columns is largely due to coagulation/breakage, which in turn determines the characteristics of the flow field in the column. This document is highly rated by Class 12 students and has been viewed 2849 times. Figure 11.2 schematically represents the enhanced coagulation process for removing arsenic from water. What Is Coagulation and Flocculation in Water and Wastewater Treatment? Calcium phosphate is another reagent that has been used for the release of Ca2+ ions to coagulate alumina suspensions stabilized in the acidic region with HCl (Xu et al., 2012a). Through this mechanism the electrolytic ions compress the electrical double layer of the particle surfaces and thus reduces the repulsion of the electrical double layer between the particles in the medium, resulting in the lowering of … The document Solved Examples : Surface Chemistry (IIT-JEE & AIPMT) Class 12 Notes | EduRev is a part of the Class 12 Course Chemistry Class 12. Alumina fiber-reinforced silica matrix composites with improved mechanical properties were prepared by this method (Xiao et al., 2017) using the Ca2+ released by calcium iodate and the hydrolysis decomposition of glycerol diacetate (GDA) thermally activated at 70°C. SURFACE CHEMISTRY . The minerals used in this step should be charged positively in a wide pH range. At high coagulant dose where sweep floc conditions prevailed, AOM removal was considerably higher and controlled by coagulant dose rather than coagulation mode.39, D. Shekhawat, P. Srivastava, in Encyclopedia of Separation Science, 2000. Coagulation of Lyophilic sols. Basically, coagulation is a process of addition of coagulant to destabilize a stabilized charged particle. (d) from zero to one. … Coagulation is generally brought brought by the addition of electrolyte. (1) By electrophoresis: In electrophoresis the colloidal particles move … NEET Chemistry Chapter Wise Mock Test – Surface Chemistry. Such coagulates consist of both fine and coarse particles. Solution: a. Tyndall Effect: When an intense converging beam of light is passed through a … Types of Colloids are Sol, Emulsion, Foam, and Aerosol. Written by AOS Treatment Solutions on April 3, 2018. The concentration of this inactive proteinase inhibitor complex (T-AT) gives an indication of the degree of coagulation system activation. Particles are not needed in DAF processes agent completely Elsevier B.V. or its licensors or contributors new... 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