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✍️Notes on Environmental Chemistry: 🔹Components of Environment: ➖Atmosphere: This comprises a blanket of gaseous layer around earth. ➖Hydrosphere: This comprises about 96% of earth’s surface & includes all sources of water like oceans rivers lakes, glaciers, ground water etc. ➖Lithosphere: It refers to earth’s solid crust containing the outer mineral cover. It comprises soil, minerals, organic matter etc. ➖ Biosphere: It refers to the domain of living organism in covalent with atmosphere hydrosphere as well as lithosphere.  🔹Environmental Pollution : Process of contamination of the environment with harmful wastes arising mainly from human activities. ➖Pollutant:  Any substance or species produced either by a natural source or by human activity, which produces adverse effect on the environment. ➖Contaminant: A substance which does not occurs in nature but is introduced by human activity into the atmosphere affecting its composition. ➖Source: The site from which the pollution or contaminants originate. ➖Sink: The material or medium which consumes or interacts with a long lived pollutant is called sink. ➖Receptor : Anything that is affected by the pollutants. ➖Threshold limit value (TLV) : This indicates the permissible limit of a pollutant in atmosphere to which a healthy worker is exposed during hours a day or 40 hours a week for life time without any adverse effects. TLV are determined by experimentation on animals, by use of medical knowledge, epidemiology surveys & environmental studies.  🔹Tropospheric pollution or Air pollution: It is the atmosphere condition in which the presence of certain concentration produce harmful effects on man and his environment. These substances include: (i) Gases such as oxides of sulphur, CO, oxide of N2 and hydrocarbons (ii)  Particulate matter such as dust, smoke, fumes etc. (iii) Radioactive material & many others. ➖Primary pollutants : These are the pollutants which are emitted directly from the sources. Some examples are: ➖Particulate Matter : Such as ash, smoke, dust, fumes etc. ➖Inorganic gases : Such as sulphur dioxide, carbon monoxide etc. 🔹Particulate matter: ➖Soot: produced by incomplete combustion of carbonaceous fossils fuels such as coal, fuel oil, natural gas, wood etc in insufficient supply of oxygen. ➖Metal particles: These are released by various metal finishing operation. The micro particles of toxic metal & SO2 gas present in the polluted atmosphere get absorbed on the particles rendering them highly toxic. ➖Metal oxides : They are generated by combustion of fuels containing metallic compounds. ➖Lead salts: Their source is lead tetraethyl (Pb(C2H5)4) which is added to gasoline to improve its antiknock property. In order to avoid deposition of PbO suitable amounts of C2H4Cl2 & C2H4Br2 are added to gasoline along with Pb(C2H5)4. ➖Fly ash: It originates from the combustion of high ash fossil. It contains partially burnt particles of the fuels. ➖Asbestos dust: It originates from industrial units manufacturing asbestos sheets, gaskets ropes etc. Asbestos flowing & asbestos insulations also contribute towards asbestos dust in the atmosphere. ➖Solid Hydrocarbons: These are emitted from petroleum refineries & comprise of paraffins, olefins & aromatics. ➖Dust Particulates: Originate from natural, domestic, industrial or agricultural sources. These are thrown into atmosphere by volcanic eruptions, blowing of dust by wind, mining operations etc. ➖Acid mist : Sulphuric acid mist is produced when SO3 present in the atmosphere comes in contact with moisture. Nitric acid mist is produced when oxides of nitrogen, viz, NO & NO2, undergo the series of reactions in the atmosphere. JOIN: @ETHIOPIANSTUDENTSTM

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✅ Electrolytic Cells and Electrolysis ✍️ Electrolysis is a process of passing a direct current through the electrodes to achieve a chemical reaction. It is not possible to achieve a chemical reaction when the chosen electrolyte is in a solid-state. ✍️ Aqua regia also known as royal water is a yellow-orange mixture of concentrated nitric acid and hydrochloric acid in the ratio 1:3. It is used by an alchemist to dissolve noble metals like gold and silver. ✍️ Electrodes which do not take part in the chemical reaction during electrolysis are known as inert electrodes. Gold, silver and graphite do not take part in the process, but graphite is preferred because gold and silver electrodes are expensive. ✍️ In the electrolysis of NaCl, if the electrolyte is molten NaCl, then the only ions formed after dissociation are Na+ and Cl– ions. The cathode being a negatively charged electrode attracts the positive Na+ ions and neutralizes it to form Sodium metal. ✍️ Na2SO4 dissociates into Na+ and SO42- ions in the electrolysis of aqueous Na2SO4. Na+ has much lower reduction potential than water and hence Na+ ions are not reduced at the cathode. Instead, reduction of water occurs giving out hydrogen gas at the cathode. ✍️ In the electrolysis of aqueous CuSO4, Cu2+, SO42+, H+ and OH– are the ions formed after dissociation. Copper ions have much higher reduction potential than water. Hence, these ions are easily reduced and deposited as Cu at the cathode. ✍️ Electroplating is a process that uses direct electric current to carry metal ions from anode and carry them through the electrolyte containing the metal ion to the cathode to get a coherent metal coating. ✍️ The electrolyte in electrolysis should contain the metal to be coated, gold in this case. AuCN is used because it is exceptionally stable and doesn’t resist the flow of Au+ ions from anode to cathode. ✍️ The two electrodes that are used in a Daniell cell are zinc (as anode) and copper (as cathode) electrodes which are dipped in a solution containing its own ions, generally zinc sulphate and copper sulphate. ✍️ Yes, the distance between the electrodes is directly proportional to the resistance between them. As the distance between the two electrodes increases, the resistance offered by the electrolyte increases and therefore reduces the voltage between them. Join: @EthiopianStudentsTM ✍

🔰 Important Notes on P-Block Elements – Nitric Acid 🔰 ✍️ Hyponitric acid does not exist. The rest three mentioned are commonly occurring oxoacids of nitrogen. Hyponitrous acid, H2N2O2 is an isomer tautomer of nitramide, with the structure of the former being HON = NOH. Nitrous acid, HNO2 is usually formed in the atmosphere prior conversion to nitric acid. It is highly unstable. ✍️ Nitric acid is a very weak reducing agent since it has a polar O – H bond. This breaks to donate the H+ ion which is why it is a strong oxidizing agent and a strong acid. Since there is only one cleavable O – H bond, the basicity of nitric acid is unity (one HNO3 molecule can donate only 1 H+ ion). It exists as a planar molecule in vapor phase. ✍️ The most appropriate lab scale preparation method of nitric acid, HNO3 is using an alkali nitrate salt and react it with concentration nitric acid in a glass retort. Nitrous acid being highly unstable decomposes into nitric acid. The other two sets of reaction represent the industrial process of manufacturing nitric acid i.e. Ostwald’s process. ✍️ Ostwald’s process is the name of the industrial process to manufacture nitric acid in bulk. It involves the oxidation of ammonia which forms nitric oxide. This is then reacted with more oxygen to produce nitrogen dioxide. Subsequently, nitrogen dioxide is dissolved in water to produce adequate concentrations of nitric acid. Contact process is used to produce sulfuric acid. Solvay is used to obtain sodium carbonate and Haber-Bosch to obtain ammonia. ✍️ Pt-Rh gauze sheet is widely used as the catalyst in ammonic oxidation, the first step of Ostwald’s process. Fe2O3 is used in Haber’s process; V2O5 in contact process and Zn (Hg) is used in Clemmensen reduction of aldehydes. ✍️ Experimentally, it is determined that nitric acid and water form a constant boiling azeotrope at 68% – 32% by mass composition, respectively. Here, it becomes impossible to separate water and nitric acid by distillation methods. Thus, concentrated sulfuric acid is used for dehydration and removal of water. ✍️ The products released depend on the concentration of nitric acid. In case of zinc metal, diluted nitric acid treatment release nitrous oxide and concentrated nitric acid causes the release of nitrogen dioxide. ✍️ Aluminum does not dissolve in nitric acid. This is because treatment with nitric acid results in the formation of a tough oxide layer. This oxide layer prevents it from further reacting with the oxide. Hence, the compound formed is Al2O3 i.e. aluminum (III) oxide. ✍️ Pickling of stainless steel is the process of removal of a thin layer of the alloyed metal from the surface. The common reagent used is nitric acid along with calculated amounts of hydrofluoric acid. ✍️ 1 mole of sulfur, S8 requires 48 moles of concentrated nitric acid. The reaction is given by S8 + 48HNO3 → 8H2SO4 + 48NO2 + 16H2O. 10, 4 and 20 moles of concentrated nitric acid is required to produce iodic acid, carbon dioxide and phosphoric acid from 1 mole of iodine, carbon and phosphorus, respectively. Join: @EthiopianStudentsTM ✍

60 ቀን አለህ! 👉 ፈተና ሀምሌ ከሆነ ቢያንስ 60 ቀን አለህ። 👉 ከዛሬ ጀምረህ በየቀኑ ቢያንስ 6 ሰዓት መድበህ ለፈተና ተዘጋጅ! 👉 ከ 6 ሰዓቱ ውስጥ 4 ሰዓቱን አጥና 2 ሰዓቱን የማትሪክ ጥያቄ ስራ! ፈተናው 1 ሳምንት እስኪቀረው ድረስ አሁን ያልኩህን በፅናት ካደረከው ማትሪክን ማለፍ ብቻ ሳይሆን ምናልባት ትልቁን ውጤት ታስመዘግባለህ። ዳይ ወደ ተግባር! ጥረታችሁ እንዲሳካ ተመኘንላችሁ @FutureXethiopia Join: @EthiopianStudentsTM ✍

Aptitude Reasoning Questions

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Sharpen your reasoning skills and ace your aptitude tests with our collection of practice questions. Share: @EthiopianStudentsTM Join: @EthiopianStudentsTM #AptitudeReasoning #PracticeMakesPerfect #EthiopianStudents

Aptitude Reasoning Questions.

Practice, it will make u perfect.

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