PEMBUATAN NATRIUM TIOSULFAT

PEMBUATAN NATRIUM TIOSULFAT

Asam tiosulfat tidak bisa dibentuk dengan menambahkan asam kedalam tiosulfat karena adanya dekomposisi asam bebas ini di dalam air dalam campuran S, H2S, H2Sn, SO2, dan H 2SO 4 ini bisa dibuat dengan menhilangkan air, dalam temperature rendah (-780C).
Dalam campuran garam-garam tiosulfat adalah stabil dan berasam. Tiosulfat dibuat dengan mendidihkan alkali atau larutan sulfat nitrat dengan S dan juga oksidasi polisulfida dengan udara .
Natrium tiosulfat pentahidrat (Na2SO2O 3.5H 2O) disebut dengan hypo berbentuk kristal yang sample benar dan kurang atau tidak berwarna. Titik beku 480C mudah larut dalam air dan larutannya digunakan untuk titrasi dalam analisis volumetri.
Natrium tiosulfat dalam induksi pemutihan untuk merusak Cl2 yang masuk, setelah mereka masuk dalam kolom pemutihan, sama halnya natrium tiosulfat kadang-kadang digunakan untuk memindahkan rasa dari minuman yang berklorinasi.
Natrium tiosulfat (Na2SO3) dapat dibuat dari H2SO4. H 2SO4 adalah asam yang sangat penting yang digunakan dalam induksi kimia. H2SO4 mencair pada suhu 10,50C membentuk cairan kental. H2SO4 berikatan dengan hydrogen dan tidak bereaksi dengan logam di dalam air untuk menghasilkan H2. H2SO4 menyerap air dan dapat menghasilkan gas. Ion SO4- adalah tetrahedral, mempunyai panjang ikatan 1,49 Å , mempunyai rantai pendek. Ikatan S – O memiliki 4 ikatan σ antar S dan O dan 2 ikatan π yang didelokalisasi S dan 4 atom O. Asam tiosulfat H2SO3 .tidak dapat dibentuk dengan menambahkan asam ke dalam tiosulfat karena pemisahan asam bebas dalam air ke dalam campuran S, H2S, H2Sn, SO2 dan H2SO3.
H2S + SO3 → H2S2O3
Garam yang biasa disebut tiosulfat stabil dan berjumlah banyak. Tiosulfat dibuat dengan memanaskan alkali/larutan sulfit dengan S dan juga dengan mengoksidasi polisulfida dengan air seperti reaksi berikut :
Na2S2O3 + S → Na2S2O3
2NaS3 + 3O2 → 2Na2S2O3 +2S
Selain itu natrium tiosulfat dapat dibuat dari SO2 dengan reaksi sebagai berikut :
2S02 (aq) + O2(g) → SO3(g)
Kemudian direaksikan dengan Na2SO3 dan H2O
reaksi :
2SO2 + Na2CO3 + H2O → 2NaHSO3 + CO2
produk (NaHSO3) direaksikan lagi dengan Na2CO3
reaksi :
2NaHSO3 + Na2CO3 → 2Na2SO3 + CO2 + H2O
terakhir Na2SO3 direaksikan dengan S dengan bantuan pemanasan.
Rekasi :
Na2SO3 + S Na2S2O3

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TITRASI PROTOLIT KUAT

TITRASI PROTOLIT KUAT

Protolit kuat mengalami reaksi alih proton yang sempurna dalam air yang menyebabkan terbentuknya ion hidronium dan ion hidroksida. Reaksinya seperti berikut :
Asam + H2O → basa + H3O-
Basa + H2O → asam + OH-
Titrasi protolit kuat dapat disingkat menjadiinteraksi antara ion hidronium dan ion hidroksida sebagai berikut :
H3O+ + OH- → H2O + H2O
Jalannya titrasi secara teoritis dihitung dari persamaan kesetimbangan massa dan tetapan kesetimbangn.caranya akan dilukiskan dengan membuat kurva teoritis untuk titrasi HCl 0,1 M dengan larutan baku NaOH.
Download versi lengkapnya di sini

GYPSUM [ Sulfates ]

CaSO4 - 2(H2O), Hydrated calcium Sulfate
Plaster, wall board, some cements, fertilizer, paint filler, ornamental stone, etc..
Gypsum is one of the more common minerals in sedimentary environments. It is a major rock forming mineral that produces massive beds, usually from precipitation out of highly saline waters. Since it forms easily from saline water, gypsum can have many inclusions of other minerals and even trapped bubbles of air and water.
Gypsum has several variety names that are widely used in the mineral trade.
"Selenite" is the colourless and transparent variety that shows a pearl like luster and has been described as having a moon like glow. The word selenite comes from the greek for Moon and means moon rock.
Another variety is a compact fiberous aggregate called "satin spar" . This variety has a very satin like look that gives a play of light up and down the fiberous crystals.
A fine grained massive material is called "alabaster" and is an ornamental stone used in fine carvings for centuries, even eons.

Physical Characteristics

Colour : usually white, colourless or gray, but can also be shades of red, brown and yellow
Luster : vitreous to pearly especially on cleavage surfaces
Transparency : crystals are transparent to translucent
Crystal System : monoclinic; 2/m
Crystal Habits : include the tabular, bladed or blocky crystals with a slanted parallelogram outline. The pinacoid faces dominate with jutting prism faces on the edges of the tabular crystals. Long thin crystals show bends and some specimens bend into spirals called "Ram’s Horn Selenite" Two types of twinning are common and one produces a "spear head twin" or "swallowtail twin" while the other type produces a "fishtail twin". Also massive, crusty, granular, earthy and fiberous.
Cleavage : good in one direction and distinct in two others
Fracture : uneven but rarely seen
Hardness : 2 and can be scratched by a fingernail
Specific Gravity : approx. 2.3+ (light)
Streak : white
Other : thin crystals are flexible but not elastic, meaning they can be bent but will not bend back on their own. Also some samples are fluorescent. Gypsum has a very low thermal conductivity (hence it’s use in drywall as an insulating filler). A crystal of Gypsum will feel noticeably warmer than a like crystal of quartz.
Associated Minerals : halite, calcite, sulfur, pyrite, borax and many others
Major Occurrences : include Naica, Mexico; Sicily; Utah and Colorado, USA; and many other locallities throughout the world
Best Indicators : crystal habit, flexible crystals, cleavage and hardness

HEMATITE [ Oxides and Hydroxides : Hematite ]

Fe2O3, iron Oxide; Very important ore of iron, as a pigment and as mineral specimens
Hematite has several varieties, each with their own unique names.
Hematite Rose is a circular arrangment of bladed crystals giving the appearance of the flower of a rose.
Tiger iron is a sedimentary deposit of approximately 2.2 billion years old that consists of alternating layers of silver gray hematite and red jasper, chert or even tiger eye quartz.
Kidney Ore is the massive botryoidal form and gives the appearance of lumpy kidney-like masses.
Oolitic Hematite is a sedimentary formation that has a reddish brown colour and an earthy luster and is composed of small rounded grains.
Specularite is a micaceous or flaky stone that is sparkling silver gray and sometimes used as an ornamental stone.
Hematite is an important ore of iron and it’s blood red colour (in the powdered form) lends itself well in use as a pigment. Hematite gets its name from a greek word meaning blood-like because of the colour of its powder. Ancient superstition held that large deposits of hematite formed from battles that were fought and the subsequent blood that flowed into the ground. Crystals of Hematite are considered rare and are sought after by collectors as are fine Kidney Ore specimens.

Physical Characteristics

Colour : steel or silver gray to black in some forms and red to brown in earthy forms. Sometimes tarnished with irredescent colours when in a hydrated form (called Turgite)
Luster : metallic or dull in earthy and oolitic forms
Transparency : Crystals are opaque
Crystal System : trigonal; bar 3 2/m
Crystal Habits : include tabular crystals of varying thickness sometimes twinned, micaceous (specular), botryoidal and massive. also earthy or oolitic
Cleavage : absent however there is a parting on two planes
Fracture : uneven
Hardness : 5 - 6
Specific Gravity : 5.3 (slightly above average for metallic minerals)
Streak : blood red to brownish red for earthy forms
Associated Minerals : include jasper (a variety of quartz) in banded iron formations (BIF or Tiger iron), dipyramidal quartz, rutile, and pyrite among others
Major Occurrences : especially nice specimens come from England, Mexico, Brazil, Australia and the Lake Superior region
Best Indicators : crystal habit, streak and hardness

MAGNETITE [ Oxides and Hydroxides : Spinel ]

Fe3O4, iron Oxide Major ore of iron and as mineral specimens
Magnetite is a natural magnet, hence the name, giving it a very nice distinguishing characteristic. Explaining the magnetism is not easy but here is a go at it. Remember, electricity produces magnetic fields just as magnetism produces electic fields.
Magnetite is a member of the spinel group which has the standard formula A(B)2O4. The A and B represent usually different metal ions that occupy specific sites in the crystal structure. In the case of magnetite, Fe3O4, the A metal is Fe+2 and the B metal is Fe+3; two different metal ions in two specific sites. This arrangement causes a transfer of electrons between the different irons in a structured path or vector. This electric vector generates the magnetic field.

Physical Characteristics

Colour : black
Luster : metallic to dull
Transparency : Crystals are opaque
Crystal System : isometric; 4/m bar 3 2/m
Crystal Habits : typically octahedrons but rarely rhombododecahedron and other isometric forms, most commonly found massive or granular. Twinning of octahedrons into spinel law twins is seen occassionally
Cleavage : absent although octahedral parting can be seen on some specimens
Fracture : conchoidal
Hardness : 5.5 - 6.5
Specific Gravity : 5.1+ (average for metallic minerals)
Streak : black
Other : Magnetism stronger in massive examples than in crystals, striations on crystal faces (not always seen)
Associated Minerals : talc and chlorite (schists), pyrite and hematite
Major Occurrences : include South Africa, Germany, Russia and many locallities in the USA
Best Indicators : magnetism, crystal habit and streak

IRON [Fe]

Characteristics

An : 26
N : 30 A
m : 55.845 (2) g/mol
Group No : 8
Group Name : Transition metals
Block : d-block
Period : 4
State : solid at 298 K
Colour : lustrous, metallic, greyish tinge
Classification : Metallic

Boiling Point : 3034K (2861oC)
Melting Point : 1811K (1538oC)
Density : 7.86g/cm3
Availability : Iron is available in many forms including foil, chips, sheet, wire, granules, nanosized activated powder, powder, and rod. Small and large samples of iron foil, sheet and wire (also Iron alloy in foil form and stainless steel alloys in foil, sheet, wire, wire straight cut lengths, insulated wire, mesh, rod, tube and powder form).
Hematite is an important iron mineral. The specimen is from the Montreal Mine in Hurley, Michigan USA.

Discovery Information

Who : Known to the ancients.
The first iron used by mankind, far back in prehistory, came from meteors. Cast iron was first produced in China about 550 BC, but not in Europe until the medieval period.

Name Origin

Latin : ferrum (iron). "Iron" in different languages.

Sources

Obtained from iron ores. It makes up about 34% of the of the mass of the Earth’s crust. It is the most abundant heavy metal in the universe, the tenth most abundant element. Primary sources are China (around 25%), Brazil, Australia and India followed by the USA, Canada, Sweden, South Africa, Russia and Japan. Annual production in 2005 was 1.544 million tonnes.
magnetite is an important iron mineral. These octahedral magnetite crystals are from Cerro Huanaquino Potosi, Bolivia

Abundance

Universe : 1100 ppm (by weight)
Sun : 1000 ppm (by weight)
Carbonaceous meteorite : 2.2 x 105 ppm
Earth’s Crust : 63000 ppm
Seawater : Atlantic surface : 1 x 10-4 ppm; Atlantic deep : 4 x 10-4 ppm; Pacific surface : 1 x 10-5 ppm; Pacific deep : 1 x 10-4 ppm
Human : 60000 ppb by weight 6700 ppb by atoms

Uses

Used in steel and other alloys which are used in countless products. It is essential for animals as it is the chief constituent of hemoglobin which carries oxygen in blood vessels. Iron(III) oxides are used in the production of magnetic storage in computers. They are often mixed with other compounds, and retain their magnetic properties in solution.

History

The first iron used by mankind, far back in prehistory, came from meteors. The smelting of iron in bloomeries probably began in Anatolia or the Caucasus in the second millennium BC or the latter part of the preceding one. Cast iron was first produced in China about 550 BC, but not in Europe until the medieval period. During the medieval period, means were found in Europe of producing wrought iron from cast iron (in this context known as pig iron) using finery forges. For all these processes, charcoal was required as fuel.
Steel (with a smaller carbon content than pig iron but more than wrought iron) was first produced in antiquity. New methods of producing it by carburizing bars of iron in the cementation process were devised in the 17th century AD. In the Industrial Revolution, new methods of producing bar iron without charcoal were devised and these were later applied to produce steel. In the late 1850s, Henry Bessemer invented a new steelmaking process, involving blowing air through molten pig iron, to produce mild steel. This and other 19th century and later processes have led to wrought iron no longer being produced.

Notes

Iron is the most used of all the metals, comprising 95 percent of all the metal tonnage produced worldwide. With the exception of a few bacteria, iron is essential to all living organisms.

Hazards

Iron dust may be harmful if inhaled.

Iron Compounds

Haemoglobin, C2952H4664N812O832S8Fe4
The iron-containing oxygen-transport metalloprotein in the red cells of the blood in mammals and other animals. Hemoglobin in vertebrates transports oxygen from the lungs to the rest of the body, such as to the muscles, where it releases the oxygen load. Hemoglobin also has a variety of other gas-transport and effect-modulation duties, which vary from species to species, and which in invertebrates may be quite diverse.
Iron(II) sulfate, FeSO4.H2O
In horticulture it is used as a lawn conditioner and moss killer, traditionally referred to as sulphate of iron. Ferrous sulfate is also used to treat iron-deficiency anemia. Side effects of therapy may include nausea and epigastric abdominal discomfort after taking iron. These side effects can be minimized by taking ferrous sulfate at bedtime. Ferrous sulfate can also be used to colour concrete. It is best used for newly cured concrete. Mix with water until saturated and spray onto concrete. The colour will range from yellow to rust.
Iron(III) chloride, FeCl3 [ Highly Corrosive & Toxic ]
Most widely used for etching copper in the production of printed circuit boards. Iron(III) chloride is also used as a catalyst for the reaction of ethylene with chlorine, forming ethylene dichloride (1,2-Dichloroethane), an important commodity chemical, which is mainly used for the industrial production of vinyl chloride, the monomer for making PVC. It is also commonly used by knife craftsmen and swordsmiths to stain blades, as to give a contrasting effect to the metal, and also to view metal layering or imperfections.
Iron(III) oxide, Fe2O3
Used in magnetic storage, for example in the magnetic layer of floppy disks. A very fine powder of ferric oxide is known as jeweller’s rouge, red rouge, or simply rouge. It is used to put the final polish on metallic jewellery and lenses, and historically as a cosmetic.

Reactions of Iron

Reactions with water
Air-free water has little effect upon iron metal. However, iron metal reacts in moist air by oxidation to give a hydrated iron oxide. This does not protect the iron surface to further reaction since it flakes off, exposing more iron metal to oxidation. This process is called rusting!
Reactions with air
Iron metal reacts in moist air by oxidation to give a hydrated iron oxide. This does not protect the iron surface to further reaction since it flakes off, exposing more iron metal to oxidation. This process is called rusting. Finely divided iron powder is pyrophoric, making it a fire risk. On heating with oxygen the result is formation of the iron oxides Fe2O3 and Fe3O4.
4Fe(s) + 3O2(g) --> 2Fe2O3(s)
3Fe(s) + 2O2(g) --> 2Fe3O4(s)
 
Reactions with halogens
Iron reacts with excess of fluorine, chlorine and bromine to form Fe(III) halides.
2Fe(s) + 3F2(g) --> 2FeF3(s)
2Fe(s) + 3Cl2(g) --> 2FeCl3(s)
2Fe(s) + 3Br2(g) --> 2FeBr3(s)
This reaction is not very successful for iodine because of thermodynamic problems. The iron(III) is too oxidizing and the iodide is too reducing. The direct reaction between iron and iodine can be used to prepare iron (II) iodide.
Fe(s) + I2(s) --> FeI2(s)
 
Reactions with acids
Iron metal dissolves readily in dilute sulphuric acid in the absence of oxygen to form solutions containing the aquated Fe(II) ion together with hydrogen gas.
Fe(s) + H2SO4(aq) --> Fe2+(aq) + SO42-(aq) + H2(g)
If oxygen is present, some of the Fe(II) oxidizes to Fe(III). The strongly oxidizing concentrated nitric acid, HNO3, reacts on th surface of iron and passivates the surface.

Occurrence and Production of Iron

Occurrence
Iron is one of the most common elements on Earth, making up about 5% of the Earth’s crust. Most of this iron is found in various iron oxides, such as the minerals hematite, magnetite, and taconite. The Earth’s core is believed to consist largely of a metallic iron-nickel alloy. About 5% of the meteorites similarly consist of iron-nickel alloy. Although rare, these are the major form of natural metallic iron on the Earth’s surface.
The reason for Mars’s red colour is thought to be an iron-oxide-rich soil.
Production
Industrially, iron is produced starting from iron ores, principally haematite (nominally Fe2O3) and magnetite (Fe3O4) by a carbothermic reaction (reduction with carbon) in a blast furnace at temperatures of about 2000oC. In a blast furnace, iron ore, carbon in the form of coke, and a flux such as limestone (which is used to remove impurities in the ore which would otherwise clog the furnace with solid material) are fed into the top of the furnace, while a blast of heated air is forced into the furnace at the bottom.
In the furnace, the coke reacts with oxygen in the air blast to produce carbon monoxide:
6C + 3O2 --> 6CO
The carbon monoxide reduces the iron ore (in the chemical equation below, hematite) to molten iron, becoming carbon dioxide in the process:
6CO + 2Fe2O3 --> 4Fe + 6CO2
The flux is present to melt impurities in the ore, principally silicon dioxide sand and other silicates. Common fluxes include limestone (principally calcium carbonate) and dolomite (calcium-magnesium carbonate). Other fluxes may be used depending on the impurities that need to be removed from the ore. In the heat of the furnace the limestone flux decomposes to calcium oxide (quicklime):
CaCO3 --> CaO + CO2
Then calcium oxide combines with silicon dioxide to form a slag.
CaO + SiO2 --> CaSiO3
The slag melts in the heat of the furnace, which silicon dioxide would not have. In the bottom of the furnace, the molten slag floats on top of the more dense molten iron, and apertures in the side of the furnace are opened to run off the iron and the slag separately. The iron once cooled, is called pig iron, while the slag can be used as a material in road construction or to improve mineral-poor soils for agriculture.
Pig iron is not pure iron, but has 4-5% carbon dissolved in it. This is subsequently reduced to steel or commercially pure iron, known as wrought iron, using other furnaces or converters. In 2005, approximately 1,544Mt (million tons) of iron ore was produced worldwide. China was the top producer of iron ore with atleast one-fourth world share followed by Brazil, Australia and India, reports the British Geological Survey.

Isotopes of Iron

54Fe [28 neutrons]
Abundance : 5.8%
Half life : 3.1 x 1022 years [ Double Electron Capture ]
Decay Energy : ? MeV
Decays to 54Cr.
55Fe [29 neutrons]
Abundance : synthetic
Half life : 2.73 years [ Electron Capture ]
Decay Energy : 0231 MeV
Decays to 55Mn.
56Fe [30 neutrons]
Abundance : 91.72%
Stable with 30 neutrons
57Fe [31 neutrons]
Abundance : 2.2%
Stable with 31 neutrons
58Fe [32 neutrons]
Abundance : 0.28%
Stable with 32 neutrons
59Fe [33 neutrons]
Abundance : synthetic
Half life : 44.503 days
Decay Energy : 1.565 MeV
Decays to 59Co.
60Fe [34 neutrons]
Abundance : synthetic
Half life : 1.5 x 106 years [ beta- ]
Decay Energy : 3.978 MeV
Decays to 60Co.

ASAM AMINO

Asam amino adalah suatu polimer yang tersusun oleh beberapa asam amino. Polimer ini disebut juga poliamida. Asam-asam amino bergabung dengan berbagai cara membentuk hemoglobin, hormon, enzim, otot, rambut, kuku, dan kulit. Asam Amino merupakan senyawa karbon yang mengandung gugus karboksil ( - COOH) dan gugus amina ( - NH3). Rumus umum asam amino adalah sebagai berikut:
Sifat asam amino:
1. Berwujud padat pada suhu kamar. Titik leleh di atas 200OC
2. Asam amino larut dalam air dan pelarut organik
3. Bersifat amfoter (dapat bereaksi dengan asam dan basa), karena mengandung gugus karboksil yang bersifat asam dan gugus amina yang bersifat basa dalam jumlah yang sama
4. Asam amino dapat bergabung dengan asam amino lain membentuk suatu polimer yang disebut peptida

Dua kelompok asam amino, yaitu:
1. Asam amino esensial, tidak dapat disintesis dalam tubuh manusia. Terdiri dari: valin, leusin, isoleusin, treonin, lisin, metionin, fenilalanin, triptofan, histidin, dan arginin
2. Asam amino non esensial, dapat disintesis oleh tubuh manusia. Terdiri dari: glisin, alanin, serin, asam glutamat, tirosin, sistein, dan prolin
» Struktur berbagai asam amino dapat dilihat di bawah ini:
Asam Amino Essensial
Asam Amino Non Essensial


PENAMAAN SENYAWA BINER

PENAMAAN SENYAWA BINER

Senyawa biner adalah senyawa yang dibentuk dari dua unsur. Senyawa biner dapat terbentuk dari satu unsur logam dan satu unsur non logam, atau dapat terbentuk dari dua unsur non logam. Jika unsur pertama adalah logam dan unsur lainnya non logam, maka senyawa biner tersebut umumnya berbentuk ionik atau senyawa ionik biner.

Penamaan senyawa biner logam dan non logam
Penamaan senyawa biner antara logam dan non logam dapat dilakukan dengan cara berikut:
1. tuliskan nama unsur logam tanpa modifikasi apapun, kemudian diikuti nama unsur non logam dengan tambahan akhiran ”ida”.
2. unsur-unsur non logam dengan bilangan oksidasi lebih dari satu jenis, maka bilangan oksidasinya ditulis dengan angka romawi. Contoh: CrCl3 : Kromium(III)Clorida, FeS : Besi(II)Sulfida dan FeF3 : Besi(III)Florida
Di samping itu, penamaan unsur-unsur logam yang memiliki bilangan oksidasi lebih dari satu jenis dapat juga dituliskan sebagai berikut:
1. jika unsur logam memiliki bilangan oksidasi kecil, diberi akhiran ”o”
2. jika unsur logam memiliki bilangan oksidasi besar, diberi akhiran ”i”.
Contoh : CrS = Kromosulfida, CrI = Kromiodida.

Penamaan senyawa biner non logam dan non logam
Jika dua unsur non logam membentuk senyawa biner, penulisan rumus senyawa dan penamaan senyawanya secara umum mirip dengan senyawa biner dari logam dan non logam. Cara penulisan rumus senyawanya yaitu dengan menuliskan terlebih dahulu unsur dengan bilangan oksidasi positif baru kemudian diikuti dengan unsur bilangan oksidasi negatif. Misalnya HCl adalah hidrogen klorida tidak dituliskan sebagai ClH. Beberapa unsur-unsur non logam dana membentuk lebih dari satu senyawa biner. Oleh karena itu, kita memerlukan beberapa awalan sebagai berikut:
1 = mono
2 = di
3 = tri
4 = tetra
5 = penta
6 = heksa
7 = hepta
8 = okta
9 = nona
10 = deka

Catatan : jika awalan memiliki huruf terakhir “a” atau ”o” dan unsur memiliki huruf awal ”a” atau ”o” maka kita menghilangkan huruf terakhir awalan yang digunakan. Misalnya karbon monoksida bukan karbon monooksida. Contoh : NO = Nitrogen Monoksida, N2O = Dinitrogen Monoksida

ZINCITE [ Oxides and Hydroxides ]


ZnO, zinc manganese Oxide
An ore of zinc and as mineral specimens
Zincite is a one locality mineral. Well actually that is not true. It is found at several localities around the world; and is rare and inconspicuous at all but one general site. That site is the famous zinc and manganese mines of the Sterling Hill and Franklin, New Jersey, USA area. Many rare minerals are found there and zincite although rare everywhere else, is far from rare there. So abundant was zincite that it was quickly exploited and became an important ore of zinc.

The structure of zincite consists of tetrahedrons of ZnO4. The tetrahedrons in zincite all are oriented in one direction and produce the hexagonal (six fold rotational) symmetry. The major axis is symmetrically polar and results in a hemimorphic crystal structure. In other words, there is no symmetry element, like a mirror or two fold rotational axis, perpendicular to the major axis and thus crystal faces on top of the crystal are not repeated on the bottom of the crystal. Hemimorphic crystals have different looking tops from their bottoms, as if they never completed the opposite, symmetrical, side; therefore the term hemimorphic or half shape. Other minerals besides zincite that have a hemimorphic character are the tourmalines, hemimorphite (what’s the first clue?), greenockite and wurtzite; among others.

Physical Characteristics

Colour: orange-yellow to deep red or brown
Luster: adamantine
Transparency: crystals are commonly translucent more rarely transparent
Crystal System: hexagonal; 6 m m
Crystal Habits: include rarely well shaped, over all, hemimorphic pyramidal crystals sometimes with an hexagonal prism terminated by the basal face of a pedion on one side and the sharp point of the pyramid on the other. Usually found as rounded granular crystals; also massive in veins and lamellar
Cleavage: good in three directions (prismatic)
Fracture: conchoidal
Hardness: 4
Specific Gravity: 5.4 - 5.7 (slightly heavy even for metallic minerals)
Streak: orange-yellow
Other: There is a basal parting
Associated Minerals: include calcite, rhodonite, willemite, franklinite, tephorite, pyroxmangite and other rare Sterling Hill and Franklin, New Jersey minerals
Major Occurrences: include the Sterling Hill and Franklin, New Jersey, USA locations where it is found in abundance. Some occurrences from where zincite is found but in much scarcer quantities include Tuscany, Italy; Tsumeb, Namibia; the Dick Weber Mine, Colourado, USA; Poland, Spain and Tasmania, Australia
Best Indicators: luster, colour, occurrence, associations, cleavage, parting and streak
Global Warming: Dire Prediction for the Year 3000

Global Warming: Dire Prediction for the Year 3000

By Wynne Parry (LiveScience.com)

Even if humans stop producing excess carbon dioxide in 2100, the lingering effects of global warming could span the next millennia. The results? By the year 3000, global warming would be more than a hot topic – the West Antarctic ice sheet could collapse, and global sea levels would rise by about 13 feet (4 meters), according to a new study.

Using a computer model, researchers looked at two scenarios – an end to humans’ industrial carbon dioxide emissions by 2010 and by 2100 – stretched out to the year 3000.

Even if humans were to stop emitting excess carbon dioxide – or if they figured out a way to completely capture it – the effects of global warming would continue to accumulate. That’s because previously emitted carbon dioxide lingers in the atmosphere and the oceans, unlike land, warm only gradually, according to one of the study researchers, Shawn Marshall, an associate professor of geography at the University of Calgary.

The carbon dioxide legacy

A number of gases contribute to global warming, among them carbon dioxide, methane and nitrous oxide. The study focused on carbon dioxide, because it is the principal greenhouse gas, and it can linger in the atmosphere for centuries, according to Marshall.

“Some of the carbon dioxide going into the atmosphere this century will be there still 1,000 years from now,” he said.

Marshall, lead researcher Nathan Gillett of the government agency Environment Canada, and their colleagues found that, by the year 3000, the brunt of the changes occurred in Southern Hemisphere. Not surprisingly, the 2100 scenario yielded more extreme results. In particular, the model predicted that southern oceans – the combined South Pacific, Atlantic and Indian Oceans, where the Antarctic Circumpolar Current resides – would warm considerably, with some far-reaching results.

North vs. south


The 2100 scenario highlights stark differences between the Northern and Southern hemispheres, according to Gillett.

In the north, “the changes, which will occur up to 2100, some of those will reverse partially, it will cool a little bit after 2100, the rainfall in high latitudes will tend to decrease,” he said. “The biggest ongoing change is in the Southern Hemisphere.”

This is because the Northern Hemisphere is covered primarily by land, which warms and cools more quickly than water. After emissions drop off, warming over land is expected to decline fairly quickly, Marshall said. Not so with water, which dominates the Southern Hemisphere.

The long-term warming seen there occurs because this century’s elevated temperatures would continue to propagate into the oceans for many centuries, even after warming at the surface has eased, according to Marshall.

The researchers found that warming would be concentrated most the further from the equator (at higher latitudes) at ocean depths between 0.3 and 0.9 miles (0.5 and 1.5 kilometers). The model showed these waters would warm very little by 2100 – but by 3000 they’d likely increase by 5.4 degrees Fahrenheit (3 degrees Celsius) in parts.

But this isn’t the only factor that could contribute to southern warming. A deep current from the warmer North Atlantic is moving (and would continue to do so), slowly toward the Antarctic, carrying warmer water with it. In addition, intensified winds could help mix warm waters into the southern oceans, and finally, the loss of Antarctic sea ice would allow more heat to enter the ocean, Marshall told LiveScience in an e-mail.

The researchers found, however, that the Arctic sea ice has recovered from its losses by 3000.

While the 2010 scenario calls for a sea level rise of 9.1 inches (23 cm), the 2100 scenario would generate a sea level rise of more than 3.3 feet (1 m) due to the thermal expansion of the ocean. It’s even possible the warming waters could reach the Antarctic ice, the researchers speculate. If so, the result could be the collapse of the West Antarctic ice sheet, which holds 500,000 cubic miles (2.2 million cubic kilometers) of ice. This would mean at least another 9.9 feet (3 m) of global sea level rise, according to the researchers.

If we stopped emitting carbon dioxide now, which would bring us close to the 2010 scenario, it’s unlikely the ice sheet would collapse, Gillett said.

In addition, the simultaneous warming of the south and the cooling of north may cause the intertropical convergence zone – the region where the northeasterly and southeasterly trade winds converge, forming a band of clouds or thunderstorms near the equator – to shift southward. As a result, the drying predicted for North Africa could continue even after emissions are stopped in 2100, and the region could lose an additional 30 percent of its precipitation, according to the researchers.

Confirmation needed


While the legacy effect of carbon dioxide lingering in the atmosphere has been demonstrated by others, other research has yet to predict the warming of the high-latitude southern oceans, according to Gillett and Marshall.

“It would be really important to see this in some other climate models to see if they find the same result, because every model has its own set of uncertainties,” Marshall said.

Zinc [Zn]

Characteristics

An: 30 N: 35
Am: 65.409 (4) g/mol
Group No: 12
Group Name: Transition metals
Block: d-block Period: 4
State: solid at 298 K
Colour: bluish pale grey Classification: Metallic
Boiling Point: 1180K (907oC)
Melting Point: 692.68K (419.53oC)
Superconducting temperature: 0.85K (-272.3oC)
Density: 7.14g/cm3
Availability: Zinc is available in many forms including dust, foil, granules, powder, pieces, nanosize activated powder, shot, and a mossy form.

Discovery Information

Who: Andreas Marggraf
When: 1764
Where: Germany

Name Origin

German: zin (German for tin). "Zinc" in different languages.

Sources

Found in the minerals zinc blende (sphalerite) (ZnS), calamine (ZnO), franklinite ((Fe,Mn,Zn)(Fe,Mn)2O4), smithsonite (ZnCO3), willemite (Zn2SiO4), and zincite (ZnO). The largest producers are Australia, Canada, Peru and the USA. Annual production is around 5 million tons.
A large piece of zincite, a good source of zinc.

 

Abundance

Universe: 0.3 ppm (by weight)
Sun: 2 ppm (by weight)
Carbonaceous meteorite: 180 ppm Earth’s Crust: 75 ppm
Seawater: Atlantic surface: 5 x 10-5 ppm; Atlantic deep: 1 x 10-4 ppm; Pacific surface: 5 x 10-5 ppm; Pacific deep: 5.2 x 10-4 ppm
Human: 33000 ppb by weight; 3200 ppb by atoms

Uses

Used to coat other metals (galvanizing) to protect them from rusting. Used in alloys such as brass, bronze, nickel. Also in solder, cosmetics and pigments.
Zinc Oxide is used as a white pigment in watercolours and paints. It can also be found as an over-the-counter ointment that is appplied to the exposed skin of the face or nose to prevent dehydration. It can also prevent sunburn.
Zinc Chloride (ZnCl2) is used as a deodorant and can also be used as wood preservative.
Zinc Sulfide (ZnS) is used in luminescent pigments such as those on the hands of clocks and other items that glow in the dark.
Calamine lotion, used to treat skin rashes, is a mix of Zn-(hydroxy-)carbonates and silicates.
Throat lozenges, used as remedies for the common cold, use Zinc Gluconate Glycine (C12H22O14Zn) and Zinc acetate.

History

In ancient India the production of zinc metal was very common. Many mine sites of Zawarmaala were active even during 1300-1000 BC. There are references of medicinal uses of zinc in the Charaka Samhita (300 BC). The Rasaratna Samuccaya (800 AD) explains the existence of two types of ores for zinc metal, one of which is ideal for metal extraction while the other is used for medicinal purpose. Zinc alloys have been used for centuries, as brass goods dating to 1000-1400 BC have been found in Israel and zinc objects with 87% zinc have been found in prehistoric Transylvania. Because of the low boiling point and high chemical reactivity of this metal (isolated zinc would tend to go up the chimney rather than be captured), the true nature of this metal was not understood in ancient times.
The manufacture of brass was known to the Ebi by about 30 BC, using a technique where calamine and copper were heated together in a crucible. The zinc oxides in calamine were reduced, and the free zinc metal was trapped by the copper, forming an alloy. The resulting calamine brass was either cast or hammered into shape.
Smelting and extraction of impure forms of zinc was accomplished as early as 1000 AD in India and China. In the West, impure zinc as a remnant in melting ovens was known since Antiquity, but usually discarded as worthless. Strabo mentions it as pseudo-arguros - "mock silver". The Berne zinc tablet is a votive plaque dating to Roman Gaul, probably made from such zinc remnants.
Dr John Lane is said to have carried out experiments, probably at Landore, prior to his bankruptcy in 1726. Postlewayt’s Universal Dictionary, the most authentic source of all technological information in Europe, did not mention zinc before 1751.
In 1738, William Champion patented in Great Britain a process to extract zinc from calamine in a smelter, using a technology somewhat similar to that used at Zawar zinc mines in Rajasthan. However, there is no evidence that he visited the orient.

Notes

The earth has been estimated to have 46 years supply of zinc. A chemist estimated in 2007 that at the current rate of usage, the world’s supply of zinc would be exhausted by about the year 2037.
Zinc is an essential element, necessary for sustaining all life. It is estimated that 3000 of the hundreds of thousands of proteins in the human body contain zinc.

Hazards

Zinc powder is very flammable. Zinc may be harmful if swallowed or inhaled, and may act as an irritant.

Zinc Compounds

Cadmium zinc telluride CdZnTe
A wide, direct bandgap semiconductor, it is used in a variety of applications, including radiation detectors, photorefractive gratings, electro-optic modulators and terahertz generation and detection. Cadmium zinc telluride is highly toxic to humans. It should not be ingested, nor its dust inhaled, and it should not be handled without appropriate gloves.

Mercury zinc telluride HgZnTe
Used in infrared detectors and arrays for infrared imaging and infrared astronomy.
Mercury zinc telluride has better chemical, thermal, and mechanical stability than mercury cadmium telluride. The bandgap of MZT is more sensitive to composition fluctuations than that of MCT, which may be an issue for reproducible device fabrication. MZT is less amenable than MCT to fabrication of complex heterostructures by molecular beam epitaxy.

Zinc acetate Zn(CH3COO)2.2H2O
It is often used to treat zinc deficiencies, for instance Wilson’s disease.
Industrial applications include wood preserving, manufacturing other zinc salts, polymer cross-linking, making ethylene acetate, and as a dye mordant and analytical reagent.
Zinc acetate is also found in the form of an ointment, a topical lotion. It is an anesthetic which can be used to treat minor pain.

Zinc antimonide ZnSb
It is a semiconducting intermetallic compound. It is used in transistors, infrared detectors and thermal imagers, as well as magnetoresistive devices.

Zinc hydroxide Zn(OH)2
One major use as as an absorbant in surgical dressings.

Zinc phosphate Zn3(PO4)2
Used as a corrosion resistant coating on metal surfaces either as part of an electroplating process or applied as a primer.

Zinc selenide ZnSe
Used to form light-emitting diodes and diode lasers. It emits blue light.

Zinc stearate Zn(C15H35O2)2
Zinc Stearate is a zinc soap that repels water, insoluble in alcohol, ether, soluble in benzene. It is the most powerful mold release agent among all metal soaps. It contains no electrolyte and has hydrophobic effect. Its main application areas are the plastics and rubber industry where they are used as releasing agents and lubricants which can be easily incorporated.
Zinc Stearate is also the chief ingredient in fanning powder, used by magicians and card manipulators to decrease the friction between the cards. This gives the card a smoothe, and "floating" feeling as the cards are spread for fans and/or flourishes.



Zinc sulfate ZnSO4
It is used to supply zinc in animal feeds, fertilizers, and agricultural sprays.
ZnSO4.7H2O is used in making lithopone, in coagulation baths for rayon, in electrolytes for zinc plating, as a mordant in dyeing, as a preservative for skins and leather and in medicine as an astringent and emetic.
An aqueous solution of zinc sulfate is claimed to be effective at removing moss from roofs. Spraying a mixture on moss will allow the wind to simply blow off the remaining debris, however it is not recommended for use on lawns as it is as effective at removing grass as it is moss.

Reactions of Zinc

Reactions with water
Zinc does not react with water.

Reactions with air
Zinc tarnishes in moist air. Zinc metal burns in air to form the white zinc(II) oxide, a material that turns yellow on prolonged heating.
2Zn(s) + O2(g) --> 2ZnO(s)
 
Reactions with halogens
Zinc reacts with bromine and iodine to form zinc(II) dihalides.
Zn(s) + Br2(g) --> ZnBr2(s)
Zn(s) + I2(g) --> ZnI2(s)
 
Reactions with acids
Zinc dissolves slowly in dilute sulphuric acid to form solutions containing the aquated Zn(II) ion together with hydrogen gas.
Zn(s) + H2SO4(aq) --> Zn2+(aq) + SO42-(aq) + H2(g)
The reactions of zinc with oxidizing acids such as nitric acid, HNO3, are complex and depend upon precise conditions.
Reactions with bases
Zinc dissolves in aqueous alkalis such as potassium hydroxide, KOH, to form zincates such as [Zn(OH)4]2- (although other species are also present).

Occurrence and Production of Zinc

There are zinc mines throughout the world, with the largest producers being China, Australia and Peru. In 2005, China produced almost one-fourth of the global zinc output, reports the British Geological Survey. Mines and refineries in Europe include Umicore in Belgium, Tara, Galmoy and Lisheen in Ireland, and Zinkgruvan in Sweden. Zinc metal is produced using extractive metallurgy. Zinc sulfide (sphalerite) minerals are concentrated using the froth flotation method and then usually roasted using pyrometallurgy to oxidise the zinc sulfide to zinc oxide. The zinc oxide is leached in several stages of increasingly stronger sulfuric acid (H2SO4). Iron is usually rejected as Jarosite or goethite, removing other impurities at the same time. The final purification uses zinc dust to remove copper, cadmium and cobalt. The metal is then extracted from the solution by electrowinning as cathodic deposits. Zinc cathodes can be directly cast or alloyed with aluminium.
Electrolyte solutions must be very pure for electrowinning to be at all efficient. Impurities can change the decomposition voltage enough to where the electrolysis cell produces largely hydrogen gas rather than zinc metal.
There are two common processes for electrowinning the metal, the low current density process, and the Tainton high current density process. The former uses a 10% sulfuric acid solution as the electolyte, with current density of 270-325 amperes per square meter. The latter uses 22-28% sulfuric acid solution as the electrolyte with current density of about 1000 amperes per square meter. The latter gives better purity and has higher production capacity per volume of electrolyte, but has the disadvantage of running hotter and being more corrosive to the vessel in which it is done. In either of the electrolytic processes, each metric ton of zinc production expends about 3900 kWh (14 MJ) of electric power
There are also several pyrometallurgical processes that reduce zinc oxide using carbon, then distill the metallic zinc from the resulting mix in an atmosphere of carbon monoxide. These include the Belgian-type horizontal-retort process, the New Jersey Zinc continuous vertical-retort process, and the St. Joseph Lead Company’s electrothermal process. The Belgian process requires redistillation to remove impurities of lead, cadmium, iron, copper, and arsenic. The New Jersey process employs a fractionating column, which is absent in the Belgian process, that separates the individual impurities, where they can be sold as byproducts. The St. Joseph Lead Company process heats the zinc oxide/coke mixture by passing an electric current through it rather than by coal or gas fire.
Another pyrometallurgical process is flash smelting. Then zinc oxide is obtained, usually producing zinc of lesser quality than the hydrometallurgical process. Zinc oxide treatment has much fewer applications, but high grade deposits have been successful in producing zinc from zinc oxides and zinc carbonates using hydrometallurgy.

Isotopes of Zinc

64Zn [34 neutrons]
Abundance: 48.6%
Stable with 34 neutrons
65Zn [35 neutrons]
Abundance: Synthetic
Half life: 244.26 days [ Electron Capture ]
Decay Energy: ? MeV
Decays to 65Cu.
Half life: 244.26 days [ Gamma Radiation ]
Decay Energy: 1.1155 MeV
Decays to ?.
66Zn [36 neutrons] 

Abundance: 27.9%
Stable with 36 neutrons

67Zn [37 neutrons]
Abundance: 4.1%
Stable with 37 neutrons

68Zn [38 neutrons]
Abundance: 18.8%
Stable with 38 neutrons

69Zn [39 neutrons]
Abundance: synthetic
Half life: 56.4 minutes [ beta- ]
Decay Energy: 0.906 MeV
Decays to 69Ga.

70Zn [40 neutrons]
Abundance: 0.6%
Stable with 40 neutrons
KARBONDIOKSIDA: SIFAT DAN DAMPAKNYA

KARBONDIOKSIDA: SIFAT DAN DAMPAKNYA

Masalah lingkungan hidup dewasa ini makin memerlukan perhatian. Manusia memanfaatkan berbagai sumber daya yang ada di lingkungannya untuk hidup. Kita mengambil makanan dari apa yang tumbuh dan hidup di darat dan di air. Kita menghirup oksigen dari udara. Kita menggunakan batu bara, minyak dan bahan alam lainnya untuk menghasilkan energi ataupun untuk menjalankan pabrik-pabrik. Pabrik-pabrik itu menghasilkan barang-barang yang berguna untuk meningkatkan taraf hidup dan kesejahteraan manusia. Namun dibalik itu ada sesuatu yang perlu mendapat perhatian serius dari kita, yakni hasil buangan dari pabrik tersebut yang berupa gas kabondioksida.
Lalu apa yang dapat dilakukan? Pertama perlu kita pahami bahwa proses kehidupan, industri dan kegiatan manusia berkaitan dengan perubahan kimia yang dapat dikendalikan. Demikian pula proses pengolahan limbah oleh alam merupakan proses kimia yang berlangsung sesuai dengan hukum-hukum kimia. Jadi, dengan ilmu kimia kita dapat membantu alam dalam mengolah limbah itu dalam mendukung kegiatan kita.
Pada makalah ini akan dibahas mengenai salah satu pencemar yang ada di udara, yakni gas karbondioksida, proses terbentuknya dan akibat-akibat yang ditimbulkan gas tersebut.
Senyawa CO2 adalah gas atmosfer yang terdiri dari satu atom karbon dan dua atom oksigen. Karbondioksida adalah hasil dari pembakaran senyawa organic jika cukup jumlah oksigen yang ada. Juga dihasilkan oleh berbagai mikroorganisme dalam fermentasi dan dihembuskan oleh hewan. Tumbuhan menyerap karbondioksida selama fotosintesis, memakai baik karbon maupun oksigen untuk membuat karbohidrat. Hadir di atmosfer bumi dengan konsentrasi rendah dan bertindak sebagai gas rumah kaca. Adalah bagian utama dari siklus karbon.
Beberapa hal yang akan dibahas dalam tulisan ini adalah sebagai berikut:
  1. Ciri-ciri kimia dan fisika carbon dioksida
  2. Karbondioksida dalam kajian anorganik
  3. Kegunaan karbon dioksida
  4. Karbon dioksida kaitan dengan biologi
  5. Ujian bagi gas CO2

Kebaikan gas CO2 kaitannya dengan lingkungan dan penanggulangan

Karbondioksida merupakan salah satu emisi gas rumah kaca yang berkontribusi besar terhadap pemanasan global, selain itu ada satu gas lagi yaitu gas metana yang memiliki dampak emisi 76 kali lebih hebat dari karbondioksida; simak ulasannya di sini
Download versi lengkap tentang karbondioksida di sini

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