Rabu, 28 Maret 2012

Titration


Titration is a general class of experiment where a known property of one solution is used to infer an unknown property of another solution. In acid-base chemistry, we often use titration to determine the pH of a certain solution.
A setup for the titration of an acid with a base is shown in : 

Figure %: A titration setup
We use this instrumentation to calculate the amount of unknown acid in the receiving flask by measuring the amount of base, or titrant, it takes to neutralize the acid. There are two major ways to know when the solution has been neutralized. The first uses a pH meter in the receiving flask adding base slowly until the pH reads exactly 7. The second method uses an indicator. An indicator is an acid or base whose conjugate acid or conjugate base has a color different from that of the original compound.

Titration Curves
A titration curve is drawn by plotting data attained during a titration, titrant volume on the x-axis and pH on the y-axis. The titration curve serves to profile the unknown solution. In the shape of the curve lies much chemistry and an interesting summary of what we have learned so far about acids and bases.
The titration of a strong acid with a strong base produces the following titration curve:

Figure %: Titration curve of a strong base titrating a strong acid
Note the sharp transition region near the equivalence point on the . Also remember that the equivalence point for a strong acid-strong base titration curve is exactly 7 because the salt produced does not undergo any hydrolisis reaction
However, if a strong base is used to titrate a weak acid, the pH at the equivalence point will not be 7. There is a lag in reaching the equivalence point, as some of the weak acid is converted to its conjugate base. You should recognize the pair of a weak acid and its conjugate base as a buffer. In , we see the resultant lag that precedes the equivalence point, called the buffering region. In the buffering region, it takes a large amount of NaOH to produce a small change in the pH of the receiving solution.

Figure %: Titration curve of a strong base titrating a weak acid
Because the conjugate base is basic, the pH will be greater than 7 at the equivalence point. You will need to calculate the pH using the Henderson-Hasselbalch equation, and inputting the pK b and concentration of the conjugate base of the weak acid.
The titration of a base with an acid produces a flipped-over version of the titration curve of an acid with a base. pH is decreased upon addition of the acid.
Note that the pH of a solution at the equivalence point has nothing to do with the volume of titrant necessary to reach the equivalence point; it is a property inherent to the composition of the solution. The pH at the equivalence point is calculated in the same manner used to calculate the pH of weak base solutions in calculation Ph
When polyprotic acids are titrated with strong bases, there are multiple equivalence points. The titration curve of a polyprotic acid shows an equivalence point for the each protonation:

Figure %: Titration curve of a strong base titrating a polyprotic acid
The titration curve shown above is for a diprotic acid such as H2SO4 and is not unlike two stacked . For a diprotic acid, there are two buffering regions and two equivalence points. This proves the earlier assertion that polyprotic acids lose their protons in a stepwise manner.


Selasa, 27 Maret 2012

History of Yogyakarta

History of Yogyakarta
Yogyakarta was founded in 1755 and was the capital of Mataram kingdom when the Dutch came along. The Dutch granted the kings by title Sultan of Yogyakarta territory. Yogyakarta was also the scene of Indonesia's most successful rebellions against the Dutch - firstly with Prince Diponegoro who waged a holy war against colonial rule from 1825 to 1830, and also serving as the capital of the newly independent republic after World War II when the Dutch reoccupied Batavia (Jakarta).

People have lived in Central Java and Yogyakarta area since immemorial time as over the centuries they have been attracted by the rich soil caused by the numerous volcanic eruptions. The earliest recorded history dares from the 9th century and was dominated by Hindu and Buddhist kingdoms that gave rise to the magnificent temples such as Prambanan, Ratu Boko, Kalasan, Sambisari and Borobudur found in this area. Yogyakarta itself dates back to the 18th century. In the early 18th century, Pakubuwono II ruled the Muslim Mataram Kingdom of the time. After he passed away, there was a conflict between his son and his brother, which was encouraged by the Dutch who were trying to colonize the region on a 'divide and rule' basis.

The Kingdom was divided into two regions namely Surakarta Hadiningrat kingdom under Sunan Pakubuwono III rule, and Nyayogyakarta Hadiningrat kingdom under Sultan Hamengku Buwono I rule. He was the founder of the present line of Sultans who still live in the Kraton and play important role in Javanese culture. The second kingdom was later called Yogyakarta, now better known as Yogyakarta.

After the independence of the Republic of Indonesia was proclaimed, Sri Sultan Hamengkubuwono IX and Sri Paku Alam VIII launched a statement that the Kasultanan and Kadipaten (the two royal regions), belonged to Republic of Indonesia as a part of the whole area of Indonesia Republic. Since then, it has been known as Yogyakarta Special Region and was given a provincial status in 1950 in recognition of its important role in it fighting for the independence.

Jumat, 23 Maret 2012

Jenis-jenis Supervisi Pendidikan


Jenis-jenis Supervisi
1.      Supervisi Umum atau Supervisi Pengajaran.
Supervisi umum yaitu supervisi yang dilakukan terhadap kegiatan-kegiatan atau pekerjaan yang secara tidak langsung berhubungan dengan usaha perbaikan pengajaran, seperti kegatan pengelolaan bangunan dan perlengkapan sekolah atau kantor-kantor pendidikan dan sebagainya.
Sedangkan supervisi pengajaran adalah kegiatan-kegiatan kepengewasan yang ditujukan untuk memperbaiki kondisi-kondisi –baik personil maupun materil- yang memugkinkan terciptanya situasi belajar-mengajar yang lebih baik demi tercapainya tujuan pendidikan.

2.      Supervisi Klinis
Supervisi klinis adalah supervisi yang difokuskan pada perbaikan pengajaran dengan melalui siklus yang sistematis dari tahap perencanaan, pengamatan dan analisis intelektual yang intensif terhadap penampila mengajar sebenarnya dengan tujuan untuk mengadakan modifikasi yang rasional.(richard waller)
Secara teknik supervisi klinis adalah suatu model supervisi yang terdiri atas tiga fase, yaitu (1) pertemuan perencanaan, (2) observasi kelas, (3) pertemuan balik.
Jadi menurut devinisi diatas dapat disimpulkan bahwa supervisi klinis adalah suatu proses bimbingan yang bertujuan untuk membantu pengembangan profesional guru/calon guru, khususnya dalam penampilan mengajar, berdasarkan observasi dan analisis data secara teliti dan obyektif sebagai pegangan untuk perubahan tingkah laku mengajar tersebut.


3.      Pengawasan Melekat dan Pengawasan Fungsional
Di dalam dunia pendidikan di Indonesia istilah supervisi disebut juga pengawasan atau kepengawasan. Pengawasan melekat adalah suatu pengawasan yang memang sudah melekat menjadi tugas dan tanggung jawab semua pimpinan. Oleh karena itu setiap pemimpin adalah juga sebagai pengawas, maka kepengawasan yang dilakukan itu disebut pengawasan melekat. Dengan pengawasan melekat yang efektif dan efisien dapat dicegah sedini mungkin terjadinya pemborosan, kebocoran, dan penyimpangan dalam penggunaan wewenang, tenaga, uang, dan perlengkapan milik negara sehingga dapat terbina aparat pendidikan yang tertib, bersih, dan berdaya guna.
Tujuan pengawasan melekat adalah untuk mengetahui apakah pimpinan unit kerja dapat menjalankan fungsi pengawasan dan pengendalian yang melekat padanya dengan baik sehingga bila ada penyelewengan, pemborosan, dan korupsi pimpinan unit kerja dapat mengambil tindakan koreksi sedini mungkin.
Pengawasan fungsional adalah kegiatan-kegiatan pengawasan yang dilakukan oleh orang-orang yang fungsi jabatanya sebagai pengawas. Sebagai contoh konkret tentang pengawasan fungsional dapat dilihat dalam struktur organisasi Departemen P dan K dalam struktur tersebut khususnya di lingkungan inspektorat jenderal terdapat delapan inspektorat yang masing-masing dipimpin oleh seorang inspektur. Khusus mengenai kepala sekolah mempunyai dua fungsi kepengawasan sekaligus, yaitu pengawasan melekat dan pengawasan fungsional. Kepala sekolah harus menjalankan pengawasan melekat karena ia adalah pimpinan unit atau lembaga yang paling bawah di lingkungan Departemen P dan K. Dan ia pun harus menjalankan atau berfungsi sebagai pengawas fungsional, karena kepala sekolah adalah juga sebagai pengawas atau supervisor yang membantu tugas penilik atau pengawas dari Kanwil, khususnya dalam bidang supervisi pengajaran.