ULANGAN AKHIR SEMESTER 2 TAHUN 2009/2010 SUDAH DI AMBANG PINTU

Ulangan Kenaikan Kelas (Ulangan Akhir Semester 2) sudah di ambang pintu. Bagi kelas X sebentar lagi kenaikan kelas ke kelas XI serta penjurusan program, sedangkan bagi kelas XI kenaikan ke kelas XII.

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Impact of Air Pollution by Sulfur Oxide (Sox)

Source :
http://www.chem-is-try.org/artikel_kimia/kimia_lingkungan/dampak-pencemaran-udara-oleh-belerang-oksida-sox/

Keywords: sulfur oxides, corrosive
Written by Edy Saputra Yoky on 15-10-2009

pollutants-sulfur oxides or belerangGas often written with the Sox made up of gases SO2 and SO3 gases that they both have different qualities. Strong-smelling gas SO2 and non-flammable, whereas SO3 gas is highly reactive. SO3 gas easily reacts with the water vapor in the air to form sulfuric acid or H2SO4. Sulfuric acid is highly reactive, easy to react (to eat) other objects that cause damage, such as perkaratan process (corrosion) and other chemical processes.

Sox have a characteristic strong smell, are corrosive (causes rust), toxic because it is always in the oxygen to reach the stability of gas phasa. Sox cause respiratory system disorders, if the level of 400-500 ppm would be very dangerous, 8-12 ppm cause eye irritation, smelly 3-5 ppm.

SO2 gas concentrations in the air will begin to be detected by human senses (smell the smell) when kensentrasinya ranged from 0.3 to 1 ppm. So in this case is the dominant gas SO2. However, the gas will be met with existing oxygen in the air and then SO3 gas formed through the following reaction:

2SO2 + O2 (air) -> 2SO3

The use of coal as a fuel in some industrial activities such as those in Western European countries and the United States, causing the gas levels in the air increases Sox. The reaction between gases Sox with water vapor in the air to form sulfuric acid and acid sulfite. If the sulfuric acid and acid sulfite down to earth with the fall of rain, there was what is known or denagn Acid Rain acid rain. Acid rain is very harmful because it can damage crops and soil fertility. In some industrialized countries, has a lot of acid rain became a very serious problem because it is damaging. The forest bare by the fall of acid rain will cause more severe environment.

Sox air pollution mainly comes from the use of new coal used in industrial activities, transportation, and so forth. Sulfur in the form of mineral coal iron peritis or FeS2 and can also form metal sulfide minerals such as PBS, HgS, ZnS, CuFeS2 and Cu2S. In the process of iron and steel industry (metal furnace) generated a lot of Sox because the minerals are bound metals in the form of many sulfide. In the process of melting metal sulfide converted into metal oxide. This process also eliminates sulfur and metals because of the sulfur content of the metal impurities. At high temperature metal sulfide easy dioxide into metal oxides through the following reaction:

2ZnS + 3O2 -> 2SO2 + 2ZnO

2PbS + 3O2 -> 2SO2 + 2PbO

Besides depending on the solution used coal as fuel, gas distribution Sox, into the environment also tergnatung drai meteorological conditions and local geography. Air humidity also affects the speed of change in the Sox into sulfuric acid and acid sulfite which will gather together the cloud that would eventually fall as acid rain. Acid rain is causing damage to forests in Europe (especially in Germany) because many industries of iron and steel smelting involving the use of coal or oil in the country.
Sources and exposure patterns

Although natural sources (volcanic or geothermal) may be present in some places, anthropogenic sources, the burning of fossil fuels containing sulfur, dominate the urban areas. These include:

* Source of basic (power plants, factories burning, mining and metal processing)
* Source regions (domestic and district heating)
* Source mobile (diesel engine)

Paparandan duration patterns often show regional differences and a significant season, depending on the dominant source and distribution space, the weather and the spread. At high concentrations, which lasted for several days during winter, the winter months which is stable when the spread is limited, still occurs in many parts of the world where coal is used for the heating. Sources usually dominate the area on several occasions, results in a homogeneous pattern of concentration and exposure / opening.

In contrast, the distance events, a short time from minutes to hours may occur as a result of fumigation, dissemination or direction of the wind from the primary source. The results of exposure patterns vary substantially, depending on the altitude emissions, and weather conditions. Variable while the ambient concentrations are often high in certain circumstances, particularly for local sources.

Impact of Pollution by Sulfur Oxide (Sox)

Most of the gas pollution by sulfur oxides (SOX) comes from burning fossil fuels, especially coal. The presence of water vapor in the air will result in the formation reaction of sulfuric acid and acid sulfite. His reaction is as follows:

SO2 + H2O -> H2SO3

SO3 + H2O -> H2SO4

If the sulfuric acid and acid sulfite is joined in the air condenses and then falls together so that rain water in the form of acid rain pollution can not be avoided anymore. This acid rain can damage crops, with the exception of forest plants. This forest destruction will result in the erosion of fertile soil layers.

Although the concentration of gas dispersed Sox to a low-yield environment, but if the contact time of the plant long enough damage to plants can occur. Concentration of about 0.5 ppm was able to wet the plants, even more so when the concentration of the Sox in the air environment can be seen from the emergence of spots on the leaf surface. If a long exposure time, then it will fall leaves. This will result in decreased plant productivity.

Polluted air has caused human Sox will experience a disruption in pernapasaannya system. This is because the gas is easily Sox became the acid attacks the mucous membranes in the nose, throat and other respiratory tract to the lungs. Sox gas attack that causes irritation of the affected body part.
SO2 layer and the dangers to health

SO2 has a strong influence on the health of acute and chronic. in the form of gas, SO2 can irritate the respiratory system; at high exposure (short time) affects lung function.

SO2 is a by-product H2SO4 affecting the respiratory system. Compounds, consisting of ammonium salts polinuklir or organosulfat, affect the alveoli, and as a soluble chemicals, they passed through the mucus membrane lining of the respiratory system in living organisms.

Particulate aerosols formed by gas to particle formation was found to join with the many health effects.

Globally, the sulfur compounds in a large amount into the atmosphere through human activity around 100 million metric tons of sulfur each year, primarily as a SO2 from burning coal and gas combustion exhaust gases. Large amount of sulfur compounds are also produced by volcanic activity in the form of H2S, the reform process organic materials, and biological sulfate reduction. The amount generated by these biological processes may exceed 1 million metric tons per year H2S.

Some of H2S that reaches the atmosphere quickly changed to SO2 via the reaction:

H2S + 3 / 2 O2 SO2 + H2O

reaction starts from the release of hydrogen ions by hydroxyl radicals,

HO-H2S + HS-+ H2O

which then continued with the following reaction to produce SO2

HS-+ O2 + HO-SO

SO2 + O2 SO + O

Almost half of the sulfur contained in coal in the form pyrit, FeS2, and the other half in the form of organic sulfur. Sulfur dioxide is produced by changes pyrit through the following reaction:

4FeS2 + 11O2 2 Fe2O3 + 8 SO2

Basically, all the sulfur that enters the atmosphere changed in the form of SO2 and only 1% or 2% only as SO2

Although SO2 is produced by human activities is only a small part of the SO2 is diatmosfer, but the effect is very serious because of SO2 can be directly toxic to the surrounding creatures. SO2 is diatmosfer tract irritants pernapasandan increase mucus secretion. People who have weak breathing very sensitive to high SO2 content diatmosfer. With the concentration of 500 ppm, SO2 can cause death in humans.

High enough pollution by SO2 has caused serious havoc. As happened in the valley Nerse Belgium in 1930, SO2 levels reach 38 ppm in the air and cause acute toxicity. During this period caused the death of 60 people and cattle.

Sulfur dioxide is also harmful to plants. The existence of this gas at high concentrations can kill the leaf tissue. edge of the leaf and the area between the bones of damaged leaves. Chronic SO2 causes khlorosis. Iniakan crop damage worsened with the increase of air humidity. SO2 in the air will turn into sulfuric acid. Therefore, the regions with the pollution by SO2 is high enough, the plants will be damaged by sulfuric acid aerosols.

Damage was also experienced by the building materials such as limestone, marble, dolomite will be destroyed by the SO2 from the air. The effect of this damage will appear in his appearance, structural integrity, and age of the building.

Artificial Enzymes For Industrial Process The Environmental Friendly

Source : http://www.chem-is-try.org/artikel_kimia/biokimia/artifisial-enzim-untuk-proses-industri-yang-ramah-lingkungan/

Key words: artificial enzyme, enzymes, industrial enzymes, enzyme catalysts
Written by Indygo Morie on 04-11-2009

310px-Artificial_enzymeProses industry that often cause environmental pollution such as the use of hazardous metal catalysts can be suppressed by using the enzyme, but unfortunately not many enzymes that can be used for the chemical industry. Until finally, a group of researchers from Copenhagen University chemistry department has successfully mempoduksi artificial enzyme that can directly be used for many applications.

With the group leader Professor Michael, Ph.D., and students Jeanette Bjerre and Thomas Hauch Fenger their memplubikasikan peneitian journal ChemBioChem (15/2009) with the title "" Aldehydes are oxidase Cyclodextrin mimics ".

Artificial enzymes for which no natural (not used)

Artificial enzymes are enzymes that are not as we know that there is in nature in general, this type of enzyme has differences with the other enzymes that have a catalytic power very Cleaner, and easy to produce. Researchers from Copenhagen laboratory was the first to create artificial enzyme that can accelerate the process of oxidation in the presence of simple molecules acid peroxide H2O2.

As we have seen that the oxidation process is the basis of various chemical industrial processes, from the paint industry and pharmaceutical industry. However, traditional oxidant known negative impact on the environment if not managed properly. This enzyme is highly recommended to use and very suitable to replace the traditional oxidant. Given the artificial enzyme can be made for special needs and more importantly they can be operated at normal conditions. Unlike traditional oxidant which generally requires a high temperature, high pressure and corrosive environments.

New tool ready to wear

Because until now only found an enzyme in living things in the environment. However, both the industry and microorganisme share the same challenges, so that the industry seek shortcuts to use chemicals as a catalyst. Artificial enzyme found by researchers to alternative means of Copenhagen ready to chemists and sooner or later it will increase its use.

Natural enzymes to accelerate reactions generally about 1 million times more Concept. However, this enzyme artificially accelerate the reaction to 10,000 times. However, this is not a barrier Mikael Bols professor said.

"We have developed this material since 2000. When we were successful with the creation of the first enzyme, which only accelerated the reaction up to 25 times so we thought that was going to talk about it in here, "he said.

If artificial enzyme velocity equals the speed of natural enzymes will be more important use is to be applied in the pharmaceutical industry.

A Model Lesson Plan for Teaching Phonics

Developments and Practices for the Objectives

By: Dr. Ann T. Licata

E. Developments and Practices for the Objectives: Plan (Input, Modeling - what you do to fulfill the objectives) Always start with the pupil's STRONG MODALITY

Objective #1

Given a list of words containing vowel sounds and four sets of phonograms depicting the /o/, the pupil will auditorily discriminate /o/ in the initial and medial positions of paired words by saying a key word and telling whether the beginning and medial sounds in the words sound the same or different for four out of four sets.

Development for Objective #1

The teacher will display a colorful visual stimulus depicting the beginning, middle, and end of a picture. The picture could be a snake with long eyelashes, a school bus, or train. The picture could be a drawing on the chalkboard or a poster. On the picture the teacher will label a B on the beginning of the picture, M on the middle of the picture, and E on the end of the picture. The direction of the labels will go from left to right. The teacher will think aloud and model as she pronounces four pairs of words which begin randomly with either the /o/, /a/, or /e/. As she pronounces the words, the teacher will articulate the individual sounds of the words and move under the drawing in synchronization with the pronouncing of the word. For example, as the word Ohio is pronounced, the teacher will stand under the beginning of the drawing when /o/ is said, move to the middle of the drawing when /hi/ is pronounced, and then move to the end of the drawing when /o/ is pronounced. The teacher will use her body to show how the sounds match to the three parts of the picture. The teacher will model the discrimination of one set of words. She will say, "I want to know if the following words begin the same way." She will say, the words oat and aloud. She will say, "I do not think they begin the same way."

Guided Practice for Objective #1

I will verbalize pairs of words containing the /o/ and other vowel sounds in the initial and medial positions. I will tell the pupil to nod his head if the words begin the same way. I will say the pairs of words Ohio, only; Oklahoma, about; only, every; over, ever. I will repeat Ohio and Oklahoma and ask the pupil to say the sound which comes in the beginning of the words. I will ask the pupil if he can tell me the letter for the sound and a word we can remember for the sound. (eg. /o/, o - Ohio)

I will say the following lists of words and ask the pupil to tell me where he hears the /o/. If the pupil cannot do this, I will provide help. hose, nose hole, pole tone, bone, joke, coke rose, those mole, whole cone, phone smoke, spoke

ZIRCONIUM

John Emsley, University of Cambridge, takes you on a tour of the periodic table. In this issue: Wear it sparkling on your finger, zirconium is also key to nuclear energy

The name zirconium comes from the Arabic word zargun, which refers to zircon, a golden-hued gemstone known since Biblical times. In the Middle Ages colourless gemstones of zircon were thought to be an inferior kind of diamond, but that was shown to be wrong in 1789 by German chemist, Martin Klaproth (1743-1817), who analysed one and discovered the new element, zirconium.

Klaproth was unable to isolate the metal, this was achieved by the Swedish chemist Jöns Jacob Berzelius in 1824. At the time chemists could find little use for zirconium or its chemical compounds, and so the element fell into obscurity for a century or more. Today artificial gems are made from zirconium oxide or 'cubic zirconia' and they sparkle with more brilliance than diamond though they are not as hard. What distinguishes them from real diamond is their higher density of 6.0 g cm^-3 compared with diamond's 3.52.

Cubic zirconia - a girl's best friend? © Istockphoto

A star element

Zirconium is abundant in S-type stars in which heavier elements are formed by neutron capture. Traces of the element are also present in the Sun, and rock brought back from the moon was found to have a surprisingly high zirconium content.

Down here on Earth scientists have recently discovered that zircons from the Jack Hill region of Western Australia were around 4.4 billion years old and this together with their oxygen isotope ratio of O¹⁶/O¹⁸ suggested that they could only have been formed when there was liquid water on the surface of the Earth, which is nearly 500 million years earlier than previously assumed.

Today the element is widely used, as zircon (zirconium silicate), zirconium oxide and as the metal itself.

Zircon sand is use for foundry equipment - in the heat-resistant linings for furnaces and to make foundry moulds and giant ladles. Mixed with vanadium or praseodymium, zircon makes blue and yellow pigments for glazing pottery and tiles.

Zirconium oxide, with a melting point of 2715ºC , is used to make heat-resistant crucibles, ceramics and abrasives. A red-hot crucible made from ZrO₂ can be plunged into cold water without cracking. Zirconium oxide is stronger than toughened steel and is also used for knives, scissors and golf irons. The production of pure zirconium oxide is ca 25,000 tonnes per year, some of which goes into other products, including cosmetics, antiperspirants, food packaging, and even fake gems. The paper and packaging industry finds that zirconium oxide makes good surface coatings because it has excellent water resistance and strength, and is non-toxic.

Zirconium metal has an oxidised surface which is both hard and impervious to chemical attack, making it ideal not only for use in chemical plants but also for body implants such as hip replacement joints. In the 1940s scientists discovered that the metal was ideal for use inside nuclear reactors and nuclear submarines because it does not corrode at high temperatures, nor absorb neutrons to form radioactive isotopes. Today the nuclear industry buys almost all of the metal that is produced and some nuclear reactors have more than 100km of zirconium tubing. As mined, zirconium contains 1-3 per cent hafnium, which is chemically very similar, and though it is difficult to separate the two elements this has to be done if the metal is to be used in the nuclear industry because hafnium absorbs neutrons strongly.

A few other zirconium-based materials are worth a mention. Zirconium-aluminium alloy is used for top-of-the-range bicycle frames because this alloy combines strength and lightness; and zirconium-niobium alloy is superconducting below 35K (-238ºC) and thus conducts electricity with no loss of energy. Finally, zirconium tungstate (ZrW₂O₈) actually shrinks as you heat it, at least until it reaches 700ºC when it decomposes into ZrO₂ and WO₃.

Fact file

© Murray Robertson/Visual Elements

Atomic number: 40; atomic mass: 91.224; melting point: 1852°C. Zirconium is in Group 4 of the Periodic Table and is a metal that prefers oxidation state (IV), as in the oxide, ZrO₂ and the chloride ZrCl₄, but it can exhibit lower oxidation states such as ZrCl₂ and ZrCl₃. Zirconium does not dissolve in alkalis or acids except hydrofluoric acid. The chief ores are zircon (zirconium silicate, ZrSiO₄) and baddeleyite (zirconium oxide, ZrO₂). World production of zircon is around one million tonnes a year, though only around 1 per cent of this ends up as the metal.

The Elements

John Emsley, University of Cambridge, takes you on a tour of the periodic table: Not just another form of silver, it's pure platinum

The use of platinum can be traced back to the ancient Egyptians and South Americans. News of the metal first reached Europe in 1726 when José Sánchez de la Torre y Armas, who was the assayer at the royal mint in Bogota, discovered that it was a new metal and not just a form of silver. Alluvial deposits in South America, and especially from the river Pinto, in Columbia, were rich in the metal, which was called platina del Pinto (silver of Pinto) from which platinum got its name.

Setting the standard

Platinum is so stable and resistant to corrosion that it was chosen for the standard kilogram, which is housed at the International Bureau of Weights and Measures, Paris, France. A replica kilogram weight is kept in Russia, which was originally standardised against the one in Paris. When the replica was checked a century later it was found to have decreased in weight by 17 mg (0.0017 per cent). This was probably caused by the loss of traces of osmium in the metal, which had been oxidised to volatile osmium tetroxide.

When platinum deposits were found in the Urals in 1822 it looked as though the metal might be as abundant as silver. The Russian Government even minted 1.5 million rouble coins before the project was abandoned as the price of the metal rose and exceeded the value of the coins. Today more than 70 per cent of the world's platinum comes from South Africa, where it occurs as cooperite (platinum sulfide, PtS). World production of the metal is around 185 tonnes per year.

The versatile metal

© Jupiterimages

Platinum has a variety of different uses. Most of the metal ends up in catalytic convertors for car exhausts, each of which contains less than 2 g but this provides a Pt surface area inside the convertor that is greater than the area of a football pitch. The metal catalyses the complete combustion of unburned hydrocarbons in exhaust fumes into CO₂ and water. Platinum's other uses are as cancer medicines, industrial catalysts and in jewellery.

Cisplatin

In 1962, the US chemist Barnett Rosenberg was investigating the effects of electromagnetic fields on cell division using platinum electrodes. He found cells were not dividing normally and he traced this to cis-dichlorodiamminoplatinum(II), PtCl₂(NH₃)₂, cisplatin, which had formed as a result of the chloride and ammonium ions reacting with the electrodes.

Cisplatin was approved as a cancer treatment in 1978 and has been used to treat thousands of patients with testicular, breast, head, and neck cancers, with a cure rate of over 90 per cent. Cisplatin, and similar platinum anticancer drugs, work by bonding strongly to DNA at any point where there are two guanine bases next to each other. The bound complex distorts the DNA, making replication impossible, and the platinum cannot be dislodged by DNA repair enzymes.

Industrial catalysts

Platinum acts as an efficient catalyst. For example, if platinum wire is held in methanol vapour it soon glows red hot as it catalyses the oxidation of methanol to methanal. Platinum can also cause mixtures of oxygen and hydrogen to explode, as if they had been sparked. In the chemical industry fine platinum gauze catalysts are used in the manufacture of nitric acid from ammonia. The production of silicones, benzene and xylenes also use platinum catalysts.

Platinum's success as a catalyst is not its only industrial application. Proton exchange membrane (PEM) fuel cells rely on platinum-coated carbon electrodes. Being a strong metal which resists corrosion, platinum is also used to coat turbine blades in jet engines, in balloon catheters, and pacemakers - where a 90/10 platinum/osmium alloy is used - and in some dental alloys. Like gold, platinum can be hammered into sheets of less than a micron thick and these have been used to coat the cones of space vehicles to protect against intense electromagnetic radiation.

With a growing emphasis on recycling and conserving dwindling natural resources it is important to recover as much platinum as possible to re-use. For example, of the platinum that goes into catalytic convertors, around a quarter is recovered, with the US leading the way in this form of recycling.

© Murray Robertson/Visual Elements

Fact file

Atomic number 78; atomic weight 195.078; melting point 1772ºC; boiling point ca 3800ºC. Platinum is a lustrous, silvery-white, malleable, ductile metal in Group 10 of the Periodic Table. Platinum is unaffected by air and water, but it dissolves in hot concentrated acids such as phosphoric and sulfuric acids, and in molten alkali.

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Soundbite molecules

Simon Cotton, teacher at Uppingham School, takes a look at those compounds that find themselves in the news or relate to our everyday lives. In this issue: potassium permanganate

That's a purple solution isn't it?

Yes, nowadays it's referred to as potassium manganate(VII), KMnO₄

What uses does KMnO₄ have?

A major use is as a steriliser - it's strong oxidising properties make it an effective disinfectant. Complaints such as athlete's foot and some fungal infections are treated by bathing the affected area in KMnO₄ solution. The compound is commercially available as a disinfectant, eg Condy's Fluid. In warm climates, vegetables are washed in a KMnO₄ solution to remove bacteria such as E. coli and S. aureus.

Organic chemists use KMnO₄ as a strong oxidising agent, and it also finds commercial use in the manufacture of important compounds such as saccharin, ascorbic acid (vitamin C) and benzoic acid. Baeyer's reagent is an alkaline solution of KMnO₄ and is used to detect unsaturated organic compounds, but because the solution also reacts with extraneous impurities bromine water is more commonly used. However, the reaction of KMnO₄ with alkenes is commercially important in extending the shelf life of fruit, flowers and vegetables.

How so?

Ripening fruit releases ethene, which in turn causes other fruit to ripen. This effect is at the root of the saying 'one rotten apple spoils a barrel'. This can be a nuisance when such perishable products are shipped or stored so incorporated into the containers are gas scrubbers that use porous material impregnated with potassium manganate(vii) (2-5 per cent, on alumina or zeolite) to remove ethene from the atmosphere.

C₂H₄ + 4KMnO₄ 4MnO₂ + 4KOH + 2CO₂

Usefully the scrubbers indicate when they need to be replaced because the purple colour changes to brown as the KMnO₄ is used up.

What else can KMnO₄ do?

As a strong oxidising agent it can start a fire. Drip dry glycerol (propane-1,2,3-triol) onto potassium manganate(VII) and after a short time the glycerol starts to burn, with a pink flame.

14KMnO₄ + 4C₃H₅(OH)₃ 7K₂CO₃ + 7Mn₂O₃ + 5CO₂ + 16H₂O

A similar reaction occurs with ethane-1,2-diol (ethylene glycol), which is used as antifreeze.

What use is that ?

In the 1960s, bushfire experts needed an efficient way of burning back vegetation to manage the build up of fuel well before the dry season and thus reduce the risk of large bush fires starting of their own accord. They developed a programme of 'prescribed burning' in which polythene tubes filled with KMnO₄ crystals were injected with ethane-1,2-diol just before they were dropped from aircraft over the target area. These caused fires when they fell upon vegetation.

Today these delayed aerial ignition devices are based on KMnO₄-filled ping-pong balls, which are injected with ethane-1,2-diol. The balls start burning in 20-30s.