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Januari 23, 2011

Larutan Elektrolit dan Non Elektrolit

Januari 23, 2011

A. PENGERTIAN LARUTAN

Kita sering mendengar kata larutan. Ada larutan gula, larutan garam, larutan teh. Tapi bagaimana dengan air kopi? Apakah kita menganggapnya sebagai sebuah larutan?
Suatu campuran terdiri dari dua komponen utama, yaitu zat terlarut dan zat pelarut. Jika dari contoh di atas zat terlarutnya adalah, gula, garam, teh, dan kopi; sedangkan zat pelarutnya adalah air.

Suatu zat dikatakan larutan jika campuran antara zat terlarut dan pelarutnya bersifat homogen. Artinya tidak terdapat batas antar komponennya, sehingga tidak dapat dibedakan lagi antara zat pelarut (air) dan terlarutnya. Beda halnya dengan air kopi, masih terdapat perbedaan antara keduanya, walaupun secara kasat mata, airnya sudah berubah warna menjadi hitam. Hal ini juga berlaku untuk campuran antara pasir dan air. Anda bisa menambahkan sendiri contoh-contonya. Untuk air kopi kita menyebutnya sebagai larutan heterogen/campuran .

B. PENGERTIAN LARUTAN ELEKTROLIT

Mari kita kembali ke pokok bahasan ini. Pastinya kita pernah melihat orang melakukan penangkapan ikan dengan alat setrom listrik yang sumber arusnya berasal dari aki; atau kalian pernah mendengar penyataan jika kita menyentuh stop kontak dalam kondisi tangan basah, kemungkinan besar akan kesetrom. Apa yang menjadi faktor penyebab dari semua perilaku ini? Mengapa ikan bisa mati jika alat setrom dicelupkan kedalam air? Bukankah penghantar listrik erat kaitannya dengan suatu bahan logam? Pertanyaan-pertanyaan ini akan kita bahas di sini.
Baca juga, Sel Elektrolisis Larutan Elektrolit
Suatu larutan dapat dikatakan sebagai larutan elektrolit jika zat tersebut mampu menghantarkan listrik. Mengapa zat elektrolit dapat menghantarkan listrik? Ini erat kaitannya dengan ion-ion yang dihasilkan oleh larutan elektrolit (baik positif maupun negative). Suatu zat dapat menghantarkan listrik karena zat tersebut memiliki ion-ion yang bergerak bebas di dalam larutan tersebut. ion-ion inilah yang nantinya akan menjadi penghantar. Semakin banyak ion yang dihasilkan semakin baik pula larutan tersebut menghantarkan listrik.
larutan elektrolit non elektrolit
Sumber gambar: kimia.upi.edu

C. BERBAGAI JENIS LARUTAN ELEKTROLIT

Larutan apa saja yang dapat menghantarkan listrik? Terdapat berbagai jenis larutan yang bisa menghantarkan listrik. Pembagian zat tersebut adalah sebagai berikut.

1.  Berdasarkan jenis larutan

a.  Larutan asam (zat yang melepas ion H+ jika dilarutkan dalam air), contohnya adalah:

  1. Asam klorida/asam lambung : HCl
  2. Asam florida : HF
  3. Asam sulfat/air aki : H2SO4
  4. Asam asetat/cuka : CH3COOH
  5. Asam sianida : HCN
  6. Asam nitrat : HNO3
  7. Asam posfat : H3PO4
  8. Asam askorbat/Vit C

b.   Larutan basa (zat yang melepas ion OH- jika dilarutkan dalam air), contohnya adalah:

  1. Natrium hidroksida/soda kaustik : NaOH
  2. Calcium hidroksida : Ca(OH)2
  3. Litium hidroksida : LiOH
  4. Kalium hidroksida : KOH
  5. Barium hidroksida : Ba(OH)2
  6. Magnesium hidroksida : Mg(OH)2
  7. Aluminium hidroksida : Al(OH)3
  8. Besi (II) hidroksida : Fe(OH)2
  9. Besi (III) hidroksida : Fe(OH)3
  10. Amonium hirdoksida : NH4OH

c.   Larutan garam (zat yang terbentuk dari reaksi antara asam dan basa), contohnya adalah:

  1. Natrium klorida/garam dapur : NaCl
  2. Ammonium clorida : NH4Cl
  3. Ammonium sulfat : (NH4)2SO4
  4. Calcium diklorida : CaCl2

2. Berdasarkan jenis ikatan:

  1. Senyawa ion (senyawa yang terbentuk melalui ikatan ion), contohnya adalah: NaCl, CaCl2, AlCl3, MgF2, LiF (sebagian besar berasal dari garam)
  2. Senyawa kovalen polar (senyawa melalui ikatan kovalen yang bersifat polar/memiliki perbedaan keelektronegatifan yang besar antar atom), contohnya adalah: HCl, NaOH, H2SO4, H3PO4, HNO3, Ba(OH)2 (berasal dari asam dan basa)
Baca juga, Reaksi Kimia dalam Larutan Elektrolit

D. KEKUATAN LARUTAN ELEKTROLIT

Kekauatan larutan elektrolit erat kaitannya dengan derajat ionisasi/disosiasi . Derajat ionisasi/disosiasi adalah perbandingan antara jumlah ion yang dihasilkan dengan jumlah zat mula-mula. Dapat dirumuskan sebagai berikut:

larutan elektrolit non elektrolit
Derajat ionisasi memiliki rentang antara 0 sampai 1.
Jika derajat ionsisasi suatu larutan mendekati 1 atau sama dengan 1, ini mengindikasikan bahwa zat tersebut tergolong larutan elektrolit kuat. Artinya adalah sebagian besar/semua zat tersebut terionisasi membentuk ion positif dan ion negative. Hanya sebagian kecil/tidak ada zat tersebut dalam bentuk molekul netral.

Jika derajat ionsisasi suatu larutan mendekati 0, ini mengindikasikan zat tersebut tergolong larutan elektrolit lemah. Artinya adalah hanya sebagian kecil zat tersebut yang terionsisasi menghasilkan ion positif dan ion negative. Sisanya masih berupa molekul netral.

Jika derajat ionisasi suatu larutan sama dengan 0, ini mengindikasikan zat tersebut tergolong larutan non elektrolit. Artinya adalah zat tersebut tidak mengalami ionisasi/tidak menghasilkan ion positif dan ion negative, semuanya dalam bentuk molekul netral. Perhatikan gambar di bawah ini.

larutan elektrolit non elektrolit

Gambar A : Pada larutan ini derajat ionisasinya = 1; artinya semua larutan membentuk ion-ion (positif dan negative), tidak ada dalam bentuk molekul netralnya. Gelembung yang dihasilkan banyak dan dapat menyalakan nyala lampu.

Gambar B : Pada larutan ini derajat ionisasinya mendekati 1; artinya sebagian besar larutan terionisasi membentuk ion positif dan ion negative, hanya sebagian kecil dalam bentuk molekul netralnya. Walaupun masih terdapat molekul netral, gas yang terbentuk banyak (tapi tidak sebanyak gambar A) dan dapat menyalakan lampu.

Gambar C : Pada larutan ini derajat ionisasinya mendekati 0; artinya hanya sebagian kecil yang terionsisasi membentuk ion positif dan ion negative. Sebagian besar terdapat dalam bentuk molekul netral. Gelembung yang dihasilkan sedikit, dan lampu tidak menyala.

Gambar D : Pada larutan ini derajat ionisasinya = 0; artinya tidak ada zat yang terionisasi membentuk ion positif dan ion negative, semua zat masih dalam bentuk molekul netralnya. Tidak menghasilkan gelembung dan lampu tidak menyala.
Baca juga, Animasi Kimia: Larutan Elektrolit dan Non Elektrolit

E. PEMBAGIAN LARUTAN ELEKTROLIT

Terdapat dua jenis larutan elektrolit, yaitu sebagai berikut:

1. Elektrolit kuat, karakteristiknya adalah sebagai berikut:

  1. Menghasilkan banyak ion
  2. Molekul netral dalam larutan hanya sedikit/tidak ada sama sekali
  3. Terionisasi sempurna, atau sebagian besar terionisasi sempurna
  4. Jika dilakukan uji daya hantar listrik: gelembung gas yang dihasilkan banyak, lampu menyala
  5. Penghantar listrik yang baik
  6. Derajat ionisasi = 1, atau mendekati 1
  7. Contohnya adalah: asam kuat (HCl, H2SO4, H3PO4, HNO3, HClO4); basa kuat (NaOH, Ca(OH)2, Ba(OH)2, LiOH), garam NaCl

2. Elektrolit lemah, karakteristiknya adalah sebagai berikut:

  1. Menghasilkan sedikit ion
  2. Molekul netral dalam larutan banyak
  3. Terionisasi hanya sebagian kecil
  4. Jika dilakukan uji daya hantar listrik: gelembung gas yang dihasilkan sedikit, lampu tidak menyala
  5. Penghantar listrik yang buruk
  6. Derajat ionisasi mendekati 0
  7. Contohnya adalah: asam lemah (cuka, asam askorbat, asam semut), basa lemah [Al(OH)3, NH4OH, Mg(OH)2, Be(OH)2]; garam NH4CN
Baca juga, Kumpulan Soal Materi Larutan Elektrolit dan Non Elektrolit

Sebagai tambahan, larutan non elektrolit memiliki karakteristik sebagai berikut:

  1. Tidak menghasilkan ion
  2. Semua dalam bentuk molekul netral dalam larutannya
  3. Tidak terionisasi
  4. Jika dilakukan uji daya hantar listrik: tidak menghasilkan gelembung, dan lampu tidak menyala
  5. Derajat ionisasi = 0
  6. Contohnya adalah larutan gula, larutan alcohol, bensin, larutan urea.
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Rino Safrizal
Jejaring Kimia Updated at: Januari 23, 2011

Januari 21, 2011

SODALITE [ Silicates : Tectosilicates : Sodalite ]

Januari 21, 2011
Na4Al3(SiO4)3Cl, sodium aluminium Silicate Chloride
Mineral specimens and ornamental stone
Sodalite is a scarce mineral that can be rock forming. Sodalite is named in reference to its sodium content. It is used for carvings and some jewellery pieces. Its light to dark pure blue colour is well known in the semi-precious stone trade. Sodalite is a member of the feldspathoid group of minerals. Minerals whose chemistries are close to that of the alkali feldspars but are poor in silica (SiO2) content, are called feldspathoids. As a result or more correctly as a function of the fact, they are found in silica poor rocks containing other silica poor minerals and no quartz. If quartz were present when the melt was crystallizing, it would react with any feldspathoids and form a feldspar.. Localities that have feldspathoids are few but some produce large quantities of sodalite. Sodalite, when not blue, is hard to distinguish from other feldspathoids. It is the only feldspathoid that contains chlorine. Sodalite dissolved in a dilute solution of HNO3 gives a positive chlorine test obtained from some swimming pool test kits.

Physical Characteristics

  • Colour : blue, white, gray, or even green
  • Luster : vitreous or greasy
  • Transparency : Crystals are transparent to translucent, massive specimens are opaque
  • Crystal System : Isometric; bar 4 3/m
  • Crystal Habits : Dodecahedral crystals have been found, usually massive as a rock forming mineral
  • Cleavage : poor, in six directions, but rarely seen
  • Fracture : uneven
  • Hardness : 5.5 - 6.0
  • Specific Gravity : 2.1 - 2.3
  • Streak : white
  • Other : it is the only feldspathoid to give a positive chlorine test when dissolved in a HNO2 dilute solution
  • Associated Minerals : calcite, nepheline, cancrinite and other feldspathoids
  • Major Occurrences : include Bancroft, Ontario; Mt. Vesuvius, Italy; Brazil; ice River area, British Columbia and Maine, USA
  • Best Indicators : colour if blue, lack of pyrite association (as in lazurite), hardness and associations
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Rino Safrizal
Jejaring Kimia Updated at: Januari 21, 2011

FLUORAPATITE [ Phosphates : Apatite ]

Januari 21, 2011
Ca5(PO4)3(OH,F,Cl), The fluorine rich apatite
As a source of phosphorous to be used in fertilizer, rarely as a gemstone and as a mineral specimen

apatite is actually three different minerals depending on the predominance of either fluorine, chlorine or the hydroxyl group. These ions can freely substitute in the crystal lattice and all three are usually present in every specimen although some specimens have been close to 100% in one or the other. The rather non-inventive names of these minerals are Fluorapatite, chlorapatite and hydroxylapatite. The three are usually considered together due to the difficulty in distinguishing them in hand samples using ordinary methods.

pink crystals of fluorapatite with pale blue beryl on books of muscovite crystals
An irony of the name apatite is that apatite is the mineral that makes up the teeth in all vertebrate animals as well as their bones. The name apatite comes from a Greek word meaning to decieve in allusion to its similarity to other more valuable minerals such as olivine, peridot and beryl.

apatite is widely distributed in all rock types; igneous, sedimentary and metamorphic, but is usually just small disseminated grains or cryptocrystalline fragments. Large well formed crystals though can be found in certain contact metamorphic rocks. Very gemmy crystals of apatite can be cut as gems but the softness of apatite prevents wide distribution or acceptance of apatite as a gemstone.

Physical Characteristics

  1. Colour : typically green but also yellow, blue, reddish brown and purple
  2. Luster : vitreous to greasy and gumdrop
  3. Transparency : Crystals are transparent to translucent
  4. Crystal System : hexagonal; 6/m
  5. Crystal Habits : include the typical hexagonal prism with the hexagonal pyramid or a pinacoid or both as a termination. Also accicular, granular, reniform and massive. A cryptocrystalline variety is called collophane and can make up a rock type called phosphorite and also can replace fossil fragments
  6. Cleavage : indistinct in one basal direction
  7. Fracture : conchoidal
  8. Hardness : 5
  9. Specific Gravity : approx. 3.1 - 3.2 (average for translucent minerals)
  10. Streak : white
  11. Other : An unusual "partially dissolved" look similar to the look of previously sucked on hard candy
  12. Associated Minerals : hornblende, micas, nepheline and calcite
  13. Major Occurrences : include Durango, Mexico; Bancroft, Ontario; Germany and Russia
  14. Best Indicators : crystal habit, colour, hardness and look
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Rino Safrizal
Jejaring Kimia Updated at: Januari 21, 2011

Januari 20, 2011

KOLID (JENIS & KEGUNAAN KOLOID)

Januari 20, 2011
Petunjuk Pengisian Quiz:

  1. Jawab pertanyaan di bawah ini menurut keyakinan Anda
  2. Sorot nomor quiz dengan mouse Anda untuk melihat pertanyaan secara lengkap
  3. Anda bisa melihat hasil jawaban langsung setelah menyelesaikan quiz ini dengan menekan tombol submit

    Petunjuk Pengisian skor:

    1. Jika Anda telah selesai, tuliskan hasil/skor Anda dengan memanfaatkan kotak komentar yang berada di bawah kuiz tersebut
    2. Pada bagian "Beri komentar sebagai", pilih Name/Url
    3. Masukkan Nama pada "Name" dan url blog Anda pada bagian "Url"
    4. Jika tidak mempunyai Url masukkan alamat http://rhynosblog.com (Khusus untuk siswa saya)
    5. Pada kotak komentar, sertakan profil Anda mulai dari Sekolah, tuliskan lagi nama Anda, dan Kelas
    6. Bagi siswa saya, partisipasi dalam pengisian quiz ini menjadi tambahan nilai; jadi pengisian profil pada kotak komentar harus tepat
    7. Selamat perpartisipasi dalam kuis ini


    Author : Rino Safrizal
    Jabatan : Guru Kimia
    Sekolah : SMA Bina Utama Pontianak




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    Rino Safrizal
    Jejaring Kimia Updated at: Januari 20, 2011

    KOLOID (KOMPONEN & PENGELOMPOKKAN SISTEM KOLOID)

    Januari 20, 2011
    Petunjuk Pengisian Quiz:

    • Jawab pertanyaan di bawah ini menurut keyakinan Anda
    • Sorot nomor quiz dengan mouse Anda untuk melihat pertanyaan secara lengkap
    • Anda bisa melihat hasil jawaban langsung setelah menyelesaikan quiz ini dengan menekan tombol submit

    Petunjuk Pengisian skor:
    • Jika Anda telah selesai, tuliskan hasil/skor Anda dengan memanfaatkan kotak komentar yang berada di bawah kuiz tersebut
    • Pada bagian "Beri komentar sebagai", pilih Name/Url
    • Masukkan Nama pada "Name" dan url blog Anda pada bagian "Url"
    • Jika tidak mempunyai Url masukkan alamat http://rhynosblog.com (Khusus untuk siswa saya)
    • Pada kotak komentar, sertakan profil Anda mulai dari Sekolah, tuliskan lagi nama Anda, dan Kelas
    • Bagi siswa saya, partisipasi dalam pengisian quiz ini menjadi tambahan nilai; jadi pengisian profil pada kotak komentar harus tepat
    • Selamat perpartisipasi dalam kuis ini

    Author : Rino Safrizal
    Jabatan : Guru Kimia
    Sekolah : SMA Bina Utama Pontianak





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      Rino Safrizal
      Jejaring Kimia Updated at: Januari 20, 2011

      SENYAWA TURUNAN ALKANA

      Januari 20, 2011
      Petunjuk Pengisian Quiz:

      • Jawab pertanyaan di bawah ini menurut keyakinan Anda
      • Anda bisa melihat hasil jawaban langsung setelah menyelesaikan quiz ini dengan menekan tombol submit
      • Sorot nomor quiz dengan mouse Anda untuk melihat secara lengkap
      Petunjuk Pengisian skor:
      • Jika Anda telah selesai, tuliskan hasil/skor Anda dengan memanfaatkan kotak komentar yang berada di bawah kuiz tersebut
      • Pada bagian "Beri komentar sebagai", pilih Name/Url
      • Masukkan Nama pada "Name" dan url blog Anda pada bagian "Url"
      • Jika tidak mempunyai Url masukkan alamat http://rhynosblog.com (Khusus untuk siswa saya)
      • Pada kotak komentar, sertakan profil Anda mulai dari Sekolah, tuliskan lagi nama Anda, dan Kelas
      • Bagi siswa saya, partisipasi dalam pengisian quiz ini menjadi tambahan nilai; jadi pengisian profil pada kotak komentar harus tepat
      • Selamat perpartisipasi dalam kuis ini
      Author : Rino Safrizal
      Jabatan : Guru Kimia
      Sekolah : SMA Bina Utama Pontianak


        -->




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        Rino Safrizal
        Jejaring Kimia Updated at: Januari 20, 2011

        Januari 17, 2011

        ANCAMAN GLOBAL WARMING SUDAH DI DEPAN MATA

        Januari 17, 2011
        Jejaring Kimia – Global warming menjadi isu yang hangat dibicarakan beberapa tahun terakhir ini. Global warming menjadi ketakutan terbesar seluruh makhluk hidup yang ada di bumi; bagaimana tidak, ancaman global warming, perlahan tapi pasti memporak porandakan isi bumi kita. Lihat fakta terbaru berikut ini:
        1. Lebih dari 500 orang meninggal akibat banjir dan longsor di Negara bagian Brazil
        2. Queensland, salah satu Negara bagian Australia mengalami banjir bandang setinggi lebih dari 6 meter dan menelan lebih dari 19 jiwa, menenggelamkan lebih dari 30.000 rumah warga dan membuat ribuan orang menderita akibat kehilangan tempat tinggal
        3. DI Pulau negros Filipina, dilaporkan lebih dari 51 jiwa meninggal akibat banjir dan longsor, 8.800 warga harus mengungsi di tempat penampungan
        4. Bulan lalu, di Negara bagian Eropa mendapat serangan suhu udara dingin dan salju yang tebal
        5. Terbaru, seperti yang dilansir kompasiana.com yang mengatakan bahwa banjir terbesar bulan ini baru akan terjadi pada 30 Januari 2011. Kompasiana memberitakan bahwa daerah yang dimaksud mengalami banjir ini adalah kota megapolitan Jakarta

        Fakta di atas hanya sebagian kecil dari dampak pemanasan global yang menunjukkan angka kenaikan suhu rata-rata tiap tahun yang mengkhawatirkan. Sungguh ini suatu bencana yang luar biasa. Bukan hanya manusia yang mengalami kerugian akan dampak global warming ini, seisi muka bumi sedikit banyak akan mengalami kemunduran potensi, dan musnahnya hewan yang sudah terbilang langka. Menghangatnya air laut menyebabkan terbentuknya uap air yang akan membentuk awan sehigga berpotensi menghasilkan guyuran hujan. Buktinya, seperti yang kita dengar baru-baru ini. Badai La Lina dan El Nino yang menghantam sebagian daerah Australia merupakan dampak dari suhu bumi yang semakin panas.
        ancaman global warming
        Gambar 1, sebuah foto satelit NASA yang menunjukkan Inggris yang beku karena diselimuti salju.

        Apa yang harus kita lakukan minimal untuk mengurangi dampak perubahan iklim ini ?
        Memang, sungguh sulit untuk merubah suatu kondisi yang bisa di bilang menginjak angka kritis, tapi kita bisa lakukan hal-hal sederhana yang menurut saya jika dilakukan oleh semua orang akan berdampak besar terhadap kondisi bumi. Jadi, apa yang harus kita lakukan sekarang?
        1. Mulailah dengan merubah pola perilaku kita terhadap kondisi lingkungan yang selama ini dianggap sepele oleh sebagian orang yaitu dengan tidak membuang sampah di sembarang tempat baik itu di darat maupun kekita lagi liburan di pantai; manfaatkan limbah yang masih bisa kita manfaatkan
        2. Tanam pohon, walaupun Cuma 1 pohon
        3. Jangan manja terhadap diri sendiri, maksud saya di sini adalah mengurangi emisi transportasi dengan cara memakai kendaran seperlunya. Jika jarak yang ditempuh dekat, jalan kaki aja; lebih sehat dan lebih hemat
        4. Hemat energy dan hemat sumber daya alam; konsumsi listrik, BBM, seperlunya saja
        5. Daging, menjadi penyebab terbesar global warming; kurangilah komsumsi daging, beralihlah ke yang nabati. Walaupun jarak antara mulut kita dan piring Cuma 50 cm, tapi tidak mudah untuk beralih pola makan karena ini berkaitan dengan kebiasan kita sehari-hari
        ancaman global warming

        6. Terakhir berubahlah untuk diri sendiri, orang lain dan terutama untuk bumi kita
        Save the earth, animals and stop global warming
        Jika Anda ingin mencari fakta tentang perubahan iklim, link berikut bisa membantu Anda:
        Perubahan Iklim
        Pemanasan Global
        ancaman global warming 

        Dalam Laporan PBB (FAO) tahun 2006 yang berjudul Bayangan Panjang Peternakan, PBB mencatat bahwa industri peternakan adalah penghasil emisi gas rumah kaca yang terbesar (18 %), jumlah ini lebih banyak dari gabungan emisi gas rumah kaca seluruh transportasi di seluruh dunia (13 %).
        Laporan yang baru saja dirilis oleh Watch Magazine edisi bulan November/Desember 2009 menyatakan bahwa peternakan bertanggung jawab atas sedikitnya 51 % dari pemanasan global.
        Emisi gas rumah kaca industri peternakan meliputi 9 % karbon dioksida, 37 % gas metana (efek pemanasannya 72 kali lebih kuat dari CO2), 65 % dinitrogen oksida (efek pemanasan 296 kali lebih kuat dari CO2), serta 64 % amonia penyebab hujan asam.
        Peternakan menyita 30% dari seluruh permukaan tanah di Bumi dan 33% dari area tanah yang subur dijadikan ladang untuk menanam pakan ternak. Peternakan juga penyebab dari 80% penggundulan Hutan Amazon.
        Lihat fakta tentang gas metana, yang juga menjadi kontribusi dalam meningkatkan suhu bumi, klik di sini
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        Rino Safrizal
        Jejaring Kimia Updated at: Januari 17, 2011

        Januari 16, 2011

        HIDROKARBON (Part 1)

        Januari 16, 2011
        Petunjuk Pengisian Quiz:

        • Jawab pertanyaan di bawah ini menurut keyakinan Anda
        • Anda bisa melihat hasil jawaban langsung setelah menyelesaikan quiz ini dengan menekan tombol submit
        • Sorot nomor quiz dengan mouse Anda untuk melihat secara lengkap
        Petunjuk Pengisian skor:
        • Jika Anda telah selesai, tuliskan hasil/skor Anda dengan memanfaatkan kotak komentar yang berada di bawah kuiz tersebut
        • Pada bagian "Beri komentar sebagai", pilih Name/Url
        • Masukkan Nama pada "Name" dan url blog Anda pada bagian "Url"
        • Jika tidak mempunyai Url masukkan alamat http://rhynosblog.com (Khusus untuk siswa saya)
        • Pada kotak komentar, sertakan profil Anda mulai dari Sekolah, tuliskan lagi nama Anda, dan Kelas
        • Bagi siswa saya, partisipasi dalam pengisian quiz ini menjadi tambahan nilai; jadi pengisian profil pada kotak komentar harus tepat
        • Selamat perpartisipasi dalam kuis ini
        Author : Rino Safrizal
        Jabatan : Guru Kimia
        Sekolah : SMA Bina Utama Pontianak



          Jika Anda berminat untuk memesang soal ini di blog Anda silakan klik di sini

          Posting dalam mode html
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          Rino Safrizal
          Jejaring Kimia Updated at: Januari 16, 2011

          Januari 15, 2011

          LEMBARAN ES GREENLAND TERANCAM REKOR SUHU TERTINGGI

          Januari 15, 2011
          Selama ekspedisi musim panas lima bulan ke daerah itu, Dr. Alun Hubbard
           dan sebuah tim yang terdiri dari 15 peneliti dari Universitas Aberystwyth dan Swansea di Inggris menggunakan berbagai teknik pengukuran gempa untuk mengevaluasi ketebalan, kecepatan penipisan, temperatur atmosfer dan informasi lainnya tentang lapisan es Greenland.

          Pencairan Greenland dianggap penyebab tertinggi kedua dari kenaikan permukaan laut setelah Antartika, dengan potensi gabungan kenaikan permukaan laut global hingga tujuh meter jika semuanya mencair ke lautan. Para ilmuwan seperti ahli kelautan Dr. Igor Belkin dari Universitas Pulai Rhode, AS menegaskan bahwa fenomena ini telah terjadi.

          Dr. Igor Belkin – Ahli Kelautan, Universitas Pulau Rhode, AS: Sebagai akibat dari pencairan Greenland, permukaan air laut naik. Jadi pencairan Greenland adalah kontributor utama bagi naiknya permukaan laut, yang punya dampak global terutama terhadap negara-negara yang tidak terlalu tinggi di atas permukaan laut itu.

          Supreme Master TV: Berdasarkan analisis dari pengumpulan data mereka selama lima bulan baru-baru ini, Dr. Hubbard menyimpulkan bahwa masa depan lapisan es amat suram, dengan kemunduran dan penipisan yang luas setelah berada dalam suhu tinggi yang ekstrem selama setahun. Sementara itu Dr. Belkin menjelaskan beberapa faktor yang terlibat dalam penyusutan yang cepat dari Greenland.

          Dr. Igor Belkin: Selama setengah abad terakhir atau kurang, suhu udara rata-rata di sekitar Greenland meningkat hingga sekitar dua derajat Centrigrade, dan itu kenaikan yang banyak. Sekarang, juga ada sirkulasi lautan di sekitar Greenland. Arus tersebut adalah arus Greenland Timur, arus Greenland Barat, dan lainnya. Arus tersebut berputar di Greenland dan mempengaruhi gletser, terutama gletser yang turun ke laut. Ada Arus Irminger yang panas yang membawa air panas ke Greenland, dan arus ini memanaskan gletser-gletser air pasang ini, memanaskan dari bawah, menambah pencairan dari dasarnya.

          Supreme Master TV: Penghargaan kami, Dr. Belkin, Dr. Hubbard dan rekan-rekan, yang memperingatkan kita akan situasi kritis dari lapisan es Greenland dan ancaman mereka terhadap naiknya permukaan laut global. Semoga penelitian seperti ini membantu mempercepat usaha kita untuk mengerem hal ini dan efek merugikan lain dari perubahan iklim.

          Selama konferensi video Oktober 2009 di Jerman, Maha Guru Ching Hai mendorong cara yang paling pasti untuk menghentikan kondisi darurat seperti pencairan lapisan es Greenland ini.

          Maha Guru Ching Hai: Jadi es yang sangat luas di bawah Greenland bahkan juga mencair lebih cepat dari perkiraan sebelumnya. Banyak peneliti mengatakan bahwa pada laju pemanasan saat ini, hampir tidak ada cara bagi dunia kita untuk tetap tinggal di dalam batas kenaikan suhu 2 derajat Celsius, yaitu kenaikan maksimum yang masih akan menjamin keselamatan sebagian besar kehidupan di Bumi. Tetapi meskipun keadaan kita amat berbahaya, kita masih punya waktu, jika kita bertindak sekarang. Dan solusinya masih tetap sangat mudah. Yaitu pola makan vegan - tanpa produk hewani. Hentikan pembunuhan, hentikan penyiksaan, juga hentikan percobaan terhadap hewan, percobaan terhadap hewan, hentikan memelihara hewan untuk daging atau tujuan lain apapun, kecuali untuk melindungi, mengasihi dan memelihara hewan-hewan tersebut.


          Informasi perubahan iklim dan global warming :
          http://pemanasanglobal.net
          http://perubahaniklim.net
          Read More
          Rino Safrizal
          Jejaring Kimia Updated at: Januari 15, 2011

          Januari 12, 2011

          Januari 11, 2011

          CRYOLITE [ Halides ]

          Januari 11, 2011
          Na3AlF6, sodium aluminium Fluoride
          As a aid to aluminium processing and other industrial uses and as mineral specimens
          Cryolite is an uncommon mineral of very limited natural distribution. Mostly considered a one locallity mineral, for although there are a few other minor locallities, it was only found in large quantities on the west coast of Greenland.
          It was used as a solvent of the aluminium rich ore, bauxite, which is a combination of aluminium oxides such as gibbsite, boehmite and diaspore. It is very difficult to remove atoms of aluminium from atoms of oxygen which is necessary in order to produce aluminium metal. Cryolite made an excellent flux to make the process less expensive. Now it is too rare to be used for this purpose and sodium aluminium fluoride is produced artificially to fill the void.
          A curious note about cryolite is the fact that it has a low index of refraction close to that of water. This means that if emersed in water, a perfectly clear colourless crystal of cryolite or powdered cryolite will essentially disappear. Even a specimen of cloudy cryolite will become more transparent and its edges will be less distinct, an effect similar to ice in water except that the ice floats.

          Physical Characteristics

          Colour : clear or white to yellowish, but can also be black or purple
          Luster : vitreous
          Transparency : crystals are transparent to translucent
          Crystal System : monoclinic; 2/m
          Crystal Habits :
          usually massive and as pseudo-cubic crystals, some with psuedo-octahedral truncations
          Cleavage :
          absent, but three parting directions produce what looks like a psuedo-cubic cleavage
          Fracture : uneven
          Hardness : 2.5 - 3
          pecific Gravity : 2.95 (average)
          Streak : white
          Other :
          index of refraction is 1.338 which is close to the index of refraction of water. As a consequence, clear cryolite crystals or powdered cryolite will nearly disappear in water. Also there is no salty taste which is helpful in distinguishing cryolite from the mineral halite
          Associated Minerals :
          include siderite, quartz, topaz, fluorite, chalcopyrite, galena, cassiterite, molybdenite, columbite and wolframite
          Major Occurrences :
          include Ivigtut area of Greenland and also at the foot of Pikes Peak at Creede, Colorado, USA, Mont Saint-Hilaire and Francon Quarry, Montreal, Quebec, Canada and at Miask, Russia
          Best Indicators :
          lack of salty taste, density, index of refraction, locallity and crystal habit
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          Rino Safrizal
          Jejaring Kimia Updated at: Januari 11, 2011

          Januari 08, 2011

          MALACHITE [ Carbonates ]

          Januari 08, 2011
          Cu2(CO3)(OH)2, Hydrated copper Carbonate : As mineral specimens, an important ore of copper, as an ornamental stone, a pigment and for jewellery
          Malachite is a famous and very popular semi-precious stone. It is named for the Greek word for "mallow", a green herb. Its banded light and dark green designs are one-of-a-kind, and give it a unique ornamental quality unlike that of any other stone. The light and dark green bands are so distictive that malachite maybe one of the most easily recognized minerals by the general public. A popular design of ceramic ware which imitates this banding is named after the mineral malachite. It forms the banding from subtle changes in the oxidation states of the surrounding pore waters, but the exact mechanism is still not well understood.
          Tumbled stones of malachite are possibly the most popular tumbled stones ever and are sold in litterally every rock shop around the world. Carvings and figurines of malachite are almost as common. A skilled craftsman can make the concentric malachite bands follow the curves of a work of art like contours on a rugged terrain. Although malachite art is not as precious as jade; it is hard to argue that it is less beautiful.
          Malachite is also popular in jewellery, Native American Southwestern jewellery especially. The stones inlayed in silver make a nice variance from the traditional turquoise jewellery. Instead of competing, the two green stones tend to compliment each other when placed together in the same settings. Other stones such as coral, mother-of-pearl, azurite, jasper and onyx used in the typically handcrafted jewellery also compliment malachite’s green colours.
          Although its massive carvable forms are well known, its crystalline forms are much rarer and only recently becoming widely available to the average mineral collector. One of its more unique habits is its fine acicular crusts and tufts. At times appearing as a mat of thin hairs or as a carpet of green velvet. Another unusual habit is its stalactitic habits such as pictured above.
          Many beautiful specimens of malachite contain special combinations with other minerals. Such combinations are some of the most colourful mineral assortments in the mineral world. They include such stunningly colourful minerals as dark blue azurite, sparkling black mottramite, baby blue chrysocolla, or rusty red limonite. So common is malachite that it is associated with almost every secondary copper mineral whether they are carbonate minerals or not. Malachite is found with many rare copper silicates, halides, phosphates, sulfates and carbonates such as duftite, libethenite, aurichalcite, sphaerocobaltite, kolwezite, shattuckite, atacamite, chalcophyllite, antlerite, conichalcite, rosasite, chalcosiderite, clinoclase, brochantite, graemite, liroconite, mixite and cornetite, to name a few.
          Malachite has a mineral impostor called pseudomalachite. Pseudomalachite is a copper phosphate that has a massive crystal habit and colour that are very similar to malachite’s habit and colour, although the two minerals have different structures. Pseudomalachite means "false malachite" in latin and is very rare compared to malachite.
          Malachite is an impostor of its own. It frequently pseudomorphs the closely associated mineral azurite. A pseudomorph is a mineral specimen where the original mineral has been chemically replaced by another mineral, but the outward appearance is still retained. Pseudomorph means "false shape" in latin parlance. The transformation is fascinating and sometimes leaves a nearly perfect azurite crystal shape that is actually malachite. Often the transformation is incomplete and leaves a blue/green mineral specimen unlike any other. A gem trade name is used for ornamental stones with this combination called azur-malachite. See the azurite page for a more detailed discussion of the transformation.

          Physical Characteristics

          Colour: banded light and dark green or (if crystalline), just dark green
          Luster: dull in massive forms and silky as crystals
          Transparency: opaque in massive form and translucent in crystalline forms
          Crystal System: monoclinic; 2/m
          Crystal Habits: massive forms are botryoidal, stalactitic or globular. Crystals are acicular or fibrous and form in tufts and encrustations. Frequently found as pseudomorphs of azurite
          Cleavage: good in one direction but rarely seen
          Fracture: conchoidal to splintery
          Hardness: 3.5 - 4
          Specific Gravity: 3.9+ (slightly heavy)
          Streak: green
          Other: Weakly effervesces in acid
          Associated Minerals: include limonite, chalcopyrite, bornite, native copper, calcite, cuprite, azurite, chrysocolla and many rare copper minerals such as kolwezite, shattuckite, antlerite, brochantite, graemite, aurichalcite, sphaerocobaltite, atacamite, chalcophyllite, conichalcite, rosasite, chalcosiderite, clinoclase, cornetite, duftite, libethenite, liroconite, mixite and mottramite among others
          Major Occurrences: include many classic mineral localities such as Shaba, Congo; Tsumeb, Nambia; Ural mountains, Russia; Mexico; several sites in Australia; England and several localities in the Southwestern United States especially in Arizona, USA
          Best Indicators: colour banding, softness, associations and reaction to acid

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          Rino Safrizal
          Jejaring Kimia Updated at: Januari 08, 2011

          AZURITE [ Carbonates ]

          Januari 08, 2011
          Cu3(CO3)2(OH)2, copper Carbonate Hydroxide : ornamental stone, pigment, minor ore of copper, and jewellery
          Azurite is a very popular mineral because of its unparalleled colour, a deep blue called "azure", hence its name. Azure is derived from the arabic word for blue. The colour is due to the presence of copper (a strong colouring agent), and the way the copper chemically combines with the carbonate groups (CO3) and hydroxyls (OH). Azurite has been used as a dye for paints and fabrics for eons. Unfortunately, at times its colour is too deep and larger crystals can appear black. Small crystals and crusts show the lighter azure colour well. Azurite is often associated with its colourful close cousin, malachite.
          Azurite is used in jewellery and for dyes as mentioned above. It is also an unimportant ore of copper, although its significance has been more impressive in the past. It is still considered a minor ore of copper; mostly because it is found associated with other more valuable copper ores. Fine crystal clusters, nodular specimens, and interesting and beautiful combinations with malachite are important pieces in anyone’s mineral collection. The magnificent colour of azurite is worth mentioning again as it truly is a one-of-a-kind in the mineral world. Azurite is one of those classic minerals

          Physical Characteristics

          Colour: azure, deep blue or pale blue if found in small crystals or crusts
          Luster: vitreous to dull depending on habit
          Transparency: Transparent if in thin crystals, otherwise translucent to opaque
          Crystal System: monoclinic; 2/m
          Crystal Habits: crystals are irregular blades with wedge shaped terminations. Also, aggregate crusts and radiating, botryoidal, nodular and earthy masses
          Cleavage: good in one direction and fair in another
          Fracture: conchoidal and brittle
          Hardness: 3.5 - 4
          Specific Gravity: 3.7+ (heavier than average)
          Streak: blue
          Associated Minerals: numerous and include malachite, limonite, calcite, cerussite, quartz, chalcopyrite, native copper, cuprite, chrysocolla, aurichalcite, shattuckite, liroconite, connellite and other oxidized copper minerals
          Major Occurrences: special localities produce some outstanding specimens especially from Lasal, Utah; Bisbee, Arizona and New Mexico, USA; Mexico; Tsumeb, Nambia; Shaba, Congo; Toussit, Morocco; Australia and in many locations in Europe
          Best Indicators: colour, softness, crystal habits and associations
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          Rino Safrizal
          Jejaring Kimia Updated at: Januari 08, 2011

          Januari 02, 2011

          CARBON

          Januari 02, 2011

          A. Characteristic

          An : 6
          N : 6
          Am : 12.0107 g/mol
          Group No : 14
          Group Name : (none)
          Block : p-block
          Period : 2
          State : solid at 298 K
          Colour : graphite is black, diamond is colourless
          Classification : Non-metallic
          Boiling Point : 5100K (4827oC)
          Melting Point : 3773K (3500oC)
          Density : (graphite) 2.267g/cm3
          Density : (diamond) 3.513g/cm3

          B. Sources

          Made by burning organic compounds with insufficient oxygen. Graphite deposits are found in Sri Lanka, Madagascar, Russia, South Korea, Mexico, Czech Republic and Italy. Diamonds are primarily found in South Africa, USA, Russia, Brazil, Zaire, Sierra Leone and Ghana.

          C. Abundance

          Universe : 5000 ppm
          Sun : 3000 ppm
          Atmosphere : 350 ppm
          Earth’s Crust : 480 ppm
          Seawater : Atlantic surface: 23 ppm; Atlantic deep: 26 ppm; Pacific surface: 23 ppm; Pacific deep: 28 ppm
          Human : 2.3 x 108 ppb by weight; 1.2 x 108 ppb by atoms

          D. Uses

          As carbon’s major properties very widely depending upon its form, carbon’s uses also very greatly. Carbon-14 which is radioactive is used in "carbon dating" (telling how old something is by determining the amount of Carbon-14 present in the item being tested as compared to a standard value for a similar object which is new). Other uses include pencils, diamonds, steel, controls nuclear reactions, tire colourant, plastics, paint pigments, lubricants and much more.

          E. Notes

          Carbon has many allotropes each having very different physical properties from the other. Graphite (pencil lead) for instance is one of the softest forms of carbon, while diamonds are the hardest.
          Carbon compounds are named according to the number of carbons present in the basic chain, the presence of single, double or triple bonds, whether or not the carbon chain forms a cyclic structure and the element or ions that substitute for hydrogens in the chain. A carbon compound with one carbon atom is a methyl-, two is an ethyl- , three is a propyl-, four butyl-, five penta, six hexa-, etc. Single a bonded hydrocarbon (hydrogen-carbon structure) is an alkane, double bond is an alkene and a triple bond is an alkyne.
           
          With more than eighteen million compounds of carbon registered with the Chemical Abstract Registry (CAS), there is much to say about carbon. So much in fact that there is an entire field of chemistry called organic chemistry that is devoted to these compounds. One could get a Ph.D. in organic chemistry and still feel that one had barely gotten their feet wet.

          F. Carbon Compounds

          The abundance of carbon in the universe, along with the unusual polymer-forming ability of carbon-based compounds at the common temperatures encountered on Earth, make this element the basis of the chemistry of all known life. Carbon is the fourth most abundant chemical element in the universe by mass, after hydrogen, helium, and oxygen.
          1. Carbon Dioxide CO2
          Carbon dioxide is a colourless gas which, when inhaled at high concentrations (a dangerous activity because of the associated asphyxiation risk), produces a sour taste in the mouth and a stinging sensation in the nose and throat. This is a minor component of the Earth’s atmosphere, produced and used by living things, and a common volatile elsewhere.
          2. Carbon Monoxide CO
          Carbon monoxide, though thought of as a pollutant today, has always been present in the atmosphere, chiefly as a product of volcanic activity. It occurs dissolved in molten volcanic rock at high pressures in the earth’s mantle. Carbon monoxide contents of volcanic gases vary from less than 0.01% to as much as 2% depending on the volcano. Carbon monoxide is a significantly toxic gas with poisoning being the most common type of fatal poisoning in many countries. Symptoms of mild poisoning include headaches and flu-like effects; larger exposures can lead to significant toxicity of the central nervous system and heart.

          G. Allotropes of Carbon

          1. Diamond [ C ]
          The hardest known natural mineral. Each atom is bonded tetrahedrally to four others, making a 3-dimensional network of puckered six-membered rings of atoms.
          2. Graphite [ C ]
          Named by Abraham Gottlob Werner in 1789, from the Greek word "to draw/write", for its use in pencils) is one of the most common allotropes of carbon. Unlike diamond, graphite is a conductor, and can be used, for instance, as the material in the electrodes of an electrical arc lamp. Graphite holds the distinction of being the most stable form of solid carbon ever discovered.
          Graphite is able to conduct electricity due to the unpaired fourth electron in each carbon atom. This unpaired 4th electron forms delocalised planes above and below the planes of the carbon atoms. These electrons are free to move, so are able to conduct electricity. However, the electricity is only conducted within the plane of the layers.
          Graphite powder is used as a dry lubricant. Although it might be thought that this industrially important property is due entirely to the loose interlamellar coupling between sheets in the structure, in fact in a vacuum environment (such as in technologies for use in space), graphite was found to be a very poor lubricant. This fact lead to the discovery that graphite’s lubricity is due to adsorbed air and water between the layers, unlike other layered dry lubricants such as molybdenum disulfide. Recent studies suggest that an effect called superlubricity can also account for this effect.
          When a large number of crystallographic defects bind these planes together, graphite loses its lubrication properties and becomes what is known as pyrolytic carbon, a useful material in blood-contacting implants such as prosthetic heart valves. Natural and crystalline graphites are not often used in pure form as structural materials due to their shear-planes, brittleness and inconsistent mechanical properties. In its pure glassy (isotropic) synthetic forms, pyrolytic graphite and carbon fiber graphite is an extremely strong, heat-resistant (to 3000oC) material, used in reentry shields for missile nosecones, solid rocket engines, high temperature reactors, brake shoes and electric motor brushes.
          3. Amorphous Carbon [ C ]
          Carbon that does not have any crystalline structure. As with all glassy materials, some short-range order can be observed, but there is no long-range pattern of atomic positions. Coal and soot are both informally called amorphous carbon. However, both are products of pyrolysis, which does not produce true amorphous carbon under normal conditions. The coal industry divides coal up into various grades depending on the amount of carbon present in the sample compared to the amount of impurities. The highest grade, anthracite, is about 90 percent carbon and 10% other elements. Bituminous coal is about 75-90 percent carbon, and lignite is the name for coal that is around 55 percent carbon.
          4. Fullerenes [ eg Buckminsterfullerene C60 ]
          The fullerenes are recently-discovered allotropes of carbon named after the scientist and architect Richard Buckminster Fuller, but were discovered in 1985 by a team of scientists from Rice University and the University of Sussex, three of whom were awarded the 1996 Nobel Prize in Chemistry. They are molecules composed entirely of carbon, which take the form of a hollow sphere, ellipsoid, or tube. Spherical fullerenes are sometimes called buckyballs, while cylindrical fullerenes are called buckytubes or nanotubes.
          As of the early twenty-first century, the chemical and physical properties of fullerenes are still under heavy study, in both pure and applied research labs. In April 2003, fullerenes were under study for potential medicinal use - binding specific antibiotics to the structure to target resistant bacteria and even target certain cancer cells such as melanoma.
          Fullerenes are similar in structure to graphite, which is composed of a sheet of linked hexagonal rings, but they contain pentagonal (or sometimes heptagonal) rings that prevent the sheet from being planar. Spherical fullerenes are often refered to as buckyballs. The smallest fullerene is the dodecahedron--the unique C20.
          Buckminsterfullerene (C60) was named after Richard Buckminster Fuller, a noted architect who popularized the geodesic dome.
          5. Nanotubes (buckytube) [ C ]
          Nanotubes are cylindrical carbon molecules with novel properties that make them potentially useful in a wide variety of applications (e.g., nano-electronics, optics, materials applications, etc.). They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. Inorganic nanotubes have also been synthesized.
          A nanotube (also known as a buckytube) is a member of the fullerene structural family, which also includes buckyballs. Whereas buckyballs are spherical in shape, a nanotube is cylindrical, with at least one end typically capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 50,000 times smaller than the width of a human hair), while they can be up to several centimeters in length. There are two main types of nanotubes: single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs).
          6. Aggregated diamond nanorods [ C ]
          Aggregated diamond nanorods, or ADNRs, are an allotrope of carbon believed to be the least compressible material known to humankind. They are also 0.3% denser than diamonds.
          7. Carbon nanofoam [ C ]
          Carbon nanofoam was discovered in 1997 by Andrei V. Rode and co-workers at the Australian National University in Canberra. It consists of a low-density cluster-assembly of carbon atoms strung together in a loose three-dimensional web.
          Each cluster is about 6 nanometers wide and consists of about 4000 carbon atoms linked in graphite-like sheets that are given negative curvature by the inclusion of heptagons among the regular hexagonal pattern. This is the opposite of what happens in the case of buckminsterfullerenes, in which carbon sheets are given positive curvature by the inclusion of pentagons.
          The large-scale structure of carbon nanofoam is similar to that of an aerogel, but with 1% of the density of previously produced carbon aerogels - only a few times the density of air at sea level. Unlike carbon aerogels, carbon nanofoam is a poor electrical conductor.
          8. Glassy Carbon [ C ]
          Glassy carbon is a class of non-graphitizing carbon which is widely used as an electrode material in electrochemistry, as well as for high temperature crucibles and as a component of some prosthetic devices. It was first produced by workers at the laboratories of The General Electric Company, UK, in the early 1960s, using cellulose as the starting material. A short time later, Japanese workers produced a similar material from phenolic resin. The preparation of glassy carbon involves subjecting the organic precursors to a series of heat treatments at temperatures up to 3000oC. Unlike many non-graphitizing carbons, they are impermeable to gases and are chemically extremely inert, especially those which have been prepared at very high temperatures. It has been demonstrated that the rates of oxidation of certain glassy carbons in oxygen, carbon dioxide or water vapour are lower than those of any other carbon. They are also highly resistant to attack by acids. Thus, while normal graphite is reduced to a powder by a mixture of concentrated sulphuric and nitric acids at room temperature, glassy carbon is unaffected by such treatment, even after several months.
          9. Lonsdaleite [ C ]
          Lonsdaleite is a hexagonal allotrope of the carbon allotrope diamond, believed to form when meteoric graphite falls to Earth. The great heat and stress of the impact transforms the graphite into diamond, but retains graphite’s hexagonal crystal lattice. Lonsdaleite was first identified from the Canyon Diablo meteorite at Barringer Crater (also known as Meteor Crater) in Arizona. It was first discovered in 1967. Lonsdaleite occurs as microscopic crystals associated with diamond in the Canyon Diablo meteorite; Kenna meteorite, New Mexico; and Allan Hills (ALH) 77283, Victoria Land, Antarctica meteorite. It has also been reported from the Tunguska impact site, Russia.
          10. Chaoite [ C ]
          Chaoite is a mineral believed to have been formed in meteorite impacts. It has been described as slightly harder than graphite with a reflection colour of grey to white.

          H. Reactions of Carbon

          1. Reactions with water
          Carbon, either as graphite or diamond does not react with water under normal conditions. Under more forceful conditions, the reaction becomes important. In industry, water is blown through hot coke. The resulting gas is called water gas and is a mixture of hydrogen (H2, 50%), carbon monoxide (CO, 40%), carbon dioxide (CO2, 5%), nitrogen and methane (N2 + CH4, 5%). It is an important feedstock gas for the chemical industry.
          C + H2O --> CO + H2
          This reaction is endothermic which means that the coke cools down during the reaction. To counteract this, the steam flow is replaced by air to reheat the coke allowing further reaction.
          2. Reactions with air
          Carbon, as graphite, burns in oxygen to form gaseous carbon(IV) dioxide. Carbon, as diamond, also burns in air when heated to 600-800’C to also form carbon(IV) oxide.
          C(s) + O2(g) --> CO2(g)
          When the air or oxygen is restricted then incomplete combustion to carbon monoxide (CO) occurs.
          2C(s) + O2(g) --> CO(g)
          3. Reactions with halogens
          Graphite reacts with fluorine (but none of the other halogens) at high temperatures to make a mixture of carbon tetrafluoride, CF4, together with some C2F6 and C5F12.
          C(s) + excess F2(g) --> CF4(g) + C2F6 + C5F12
          4. Reactions with acids
          Graphite reacts with hot concentrated nitric acid to form mellitic acid, C6(CO2H)6.

          I. Isotopes of Carbon

          12C [6 neutrons]
          Abundance : 98.9%
          Stable with 6 neutrons
          13C [7 neutrons]
          Abundance : 1.1%
          Stable with 7 neutrons
          14C [8 neutrons]
          Abundance : trace
          Half life: 5730 years [ beta- ]
          Decay Energy: 0.156MeV
          Decays to 14N.
          Read More
          Rino Safrizal
          Jejaring Kimia Updated at: Januari 02, 2011

          Antoine-Jerome Balard [1802-1876]

          Januari 02, 2011
          Balard was born in Montpellier in southern France, and studied there at the School of Pharmacy. After graduating in 1826, he remained at Montpellier as a demonstrator in chemistry. In 1825, while investigating the salts contained in seawater, he discovered a dark red liquid, which he proved was an element with properties similar to chlorine and iodine. Balard proposed the name 'muride' but the editors of Annales de chimie preferred 'brome' (because of the element's strong odour, from the Greek for 'stink') and the element came to be called bromine. Balard also (1834) discovered dichlorine oxide (Cl2O) and chloric(I) acid (HClO).

          In 1833 he became professor at Montpellier and in 1843 succeeded Louis Thenard at the Sorbonne as professor of chemistry. In 1854 he was appointed professor of general chemistry at the College de France, where he remained until his death.
          Read More
          Rino Safrizal
          Jejaring Kimia Updated at: Januari 02, 2011

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