CONDITIONAL SENTENCE

NAMA : SINGGIH AULLIYA SAPUTRA KELAS/NO : XI TEKNIK PEMESINAN 4 CONDITIONAL SENTENCE Conditional sentences are sentences discussing factual implication or hypotethical situation and their consequences. Conditional sentences have two part: If-Clause and Result Clause. There are three kinds of conditional sentences. Each kind contains a different pair of tenses. 1. Conditional Sentence Type 1 (Real present/ True in the present or future) • Definition : It is about something or condition that is possible to happen in the future. • Function : Give statement that there is still a real possibility and implies the action in the If-clauses is quite possible. • Formulation : If-Clause Result Clause Simple Present Will / Can + Simple form Ø If + Subject + Present tense + (,) + Subject + Future tense Example : 1. If I find the book, I will give it to you. 2. If she is here, I will be happy. 3. If they come here, we will help them. 4. If he does it, I will give him money. 5. If you leave the cage open, the bird will fly away. Ø Subject + Future tense + if +subject + Present tense Example: 1. I will help you if I have time. 2. She will be stupid if she is lazy. 3. He will do it if you visit him. 4. She will be angry if I do not visit her. 5. Rano will teach you if you come to his house. Note: event though will is same with be going to, but be going to can not be used in conditional sentences. 2. Conditional Sentence Type 2 (Unreal present/ Untrue (Contrary to Fact) in the present/ future) • Definition : It is about something or condition that is imposible to happen. • Function : Gives statement that is impossible to happen and talks about situation that are contrary to fact i.e. situation that are the opposite of the true situation. • Formulation : If-Clause Result Clause Simple Past Would/ Could + Simple form Ø If + Subject + Simple past tense + (,) + Subject + Simple past future Example : 1. If I didn’t pass the exam, I would repeat the test. ( I pass the exam, so I don’t repeat the test ) 2. If she knew it, she would tell you. ( she doesn’t know it, so she doesn’t tell you) 3. If she were my mother, I would obey her. ( She isn’t my mother, so I don’t obey her) 4. If he didn’t do it, they wouldn’t do it. ( He does’t do it, so they do it) 5. If you were here, you would tell her about it. ( You are not here, so you don’t tell her about it) Ø Subject + Simple past future + if +subject + Simple past tense 1. Elly would give him punishment if she were a teacher. ( Elly doesn’t give him punishment because she isn’t a teacher) 2. We would visit you if we knew your address. ( We don’t visit you because we don’t know your address) Note: * if the fact positive, so if conditional is negative. * Were is used for both singular and plural subject. Was is sometimes used in very informal speech but it is not generally considered grammatically acceptable. 3. Conditional Sentence Type 3 (Unreal past/ Untrue (Contrary to Fact) in the past) • Definitin : it is about something or condition that is impossible to happen in the past time. • Function : Gives statement that is impossible to happen in the past time. • Formulation : If-Clause Result Clause Past Perfect Tense Would/ Could have + Past Participle Ø If + Past Perfect tense + (,) + Past future perfect tense Example : 1. If they had come earlier, they could have met me. ( they didn’t cone earlier, so they didn’t met me) 2. If he had done my job, I would have given him money. ( he didn’t do my job. Therefore, i didn’t give him money) Ø Past future perfect tense + if + Simple perfect tense Example : 1. My father would have sold the house if he has found the right buyer. ( My father didn’t sell teh house because he didn’t find the right buy 2. I would have gone out if I hadn’t been so tired last night. ( I didn’t go out because I was so tired last night) Using progressive verb form in conditional sentence It is used in progressive condition, this form is common in type 2 conditional sentences. It expresses an unfinished or continuing action or situation, which is the probable result of unreal condition. Example : 1. She would be discussing the home work with Wahyu if she had a time. 2. They would be playing volly ball if it was holiday. 3. I would be happy if you accompanied me. Using “mixed time” in conditional sentences Sometimes Unreal Conditional sentences are mixed. This means that the time in the if-clause is not the same as the time in the result. Example: 1. If she were my mother, i would be loving her so much. 2. If Ahmad spoke English, he would have been translator. 3. I would be proud of you if you won the competition. Omiting “if” Sometime if is omitted and the subject and verb are inverted. Example: 1. Were she at home, thay would visit her. (If she were at home, thay would visit her) 2. Should he asked her, she would marry him soon. (If he asked her, she would marry him soon) 3. Had he studied hard, he would have passed the exam. (If he had studied hard, he would have passed the exam) Implied Condition Often the if-clause is implied; not started. Conditional verbs are still used in the result clause. Example: 1. I would have invited him, but i didn’t know his name. 2. She would have bough the coat, but i didn’t have enough money. 3. Ms. Ros would have punished her child, but she had to work. Using as if / as though Example: 1. She talks as if / as though she knew everything. (She doesn’t know everything or she knows nothing) 2. He sings as if / as though he were a rock singer. (He isn’t a rock singer) 3. She tells as if / as though she had attended the meeting. (She didn’t attent the meeting) Verb forms following “wish” Wish used when the speaker wants reality to be different, to be exactly to be opposite. There are three types of wish: 1. The future time form: Subject + wish + subject + would ..... Could ..... Example: a. I wish Merry come to my office to interview. b. It is raining, I wish it would stop. c. I wish you to hurry. 2. The present time form: Subject + wish + subject + past tense ..... Example: a. I wish I knw how to do it. b. I wish Amir were here. c. She wishes she could answer the question. 3. The past time form: Subject + wish + subject + past perfect tense...... Example: a. I wish she had knocked the door before she enter the room. b. They wish we had not forgotten his tasks. c. She wishes she had been in Bali to holiday. Using would to make wishes about the future “Would” is usually used to indicate that the speaker wants something to happen or someone other than the speaker to do something in the future. The wish may or may not come true (be realized). Example: 1. It is going to be a good movie. I wish it would be watched television tonight. 2. It is snowing. I wish it would make us play in the park. 3. They were going to go to Mecca. I wish they would not be forget me.

noun clouses

NAMA: SINGGIH AULLIYA SAPUTRA KELAS/NO: XI TP4/ 17 Definition of noun clouses: A dependent clause that functions as a noun (that is, as a subject, object, or complement) within a sentence. Also known as a nominal clause. Noun clauses are subordinate or dependent clauses that perform eight main functions in English grammar. Noun clauses may be finite or nonfinite depending on the form of the verb in the clause. The following article defines the two forms and eight functions of noun clauses in the English language. English Noun Clauses Noun clauses are subordinate or dependent clauses that are formed by a subordinating conjunction followed by a clause. The english subordinating conjunctions that introduce noun clauses are that (which can be omitted in certain cases), if, whether, wh- words, wh-ever words, and sometimes for. Noun clauses may be either finite or nonfinite in form. Noun clauses perform many of the same functions as nouns and noun phrases. Functions prototypically performed by nouns and noun phrases are called nominal functions. The eight functions of nouns clauses are: 1. Subject 2. Subject complement 3. Direct object 4. Object complement 5. Indirect object 6. Prepositional complement 7. Adjective phrase complement 8. Noun phrase complement The following sections discuss the two grammatical forms and eight grammatical functions of noun clauses and include examples to illustrate use. Finite The first grammatical form of noun clauses in English grammar is the finite noun clause. Finite noun clauses contain conjugated verb phrases. Conjugated verb phrases in English show person (first, second, third), number (singular, plural), and tense (present, past). The following italicized clauses are examples of finite noun clauses: o My favorite musician is whoever sings this song. o Whatever you decide is fine with me. o His parents are fuming about how he crashed their new car. The finite, or conjugated, verbs in the noun clauses are sings (first person singular present), decide (second person singular/plural present), and crashed (third person singular past). Nonfinite The second grammatical form of noun clauses in English grammar is the nonfinite noun clause. Nonfinite noun clauses lack conjugated verbs. Nonfinite verbs in English include base forms (verb), infinitives (to + verb), and present participles (verb-ing). The following italicized clauses are examples of nonfinite noun clauses: o The teacher wants you to finish your homework. o My mom listened to me singing the song. o I demand that the child eat his vegetables.* The nonfinite, or unconjugated, verbs in the noun clauses are to finish (infinitive), singing (present participle), and eat (base). Notice also that the object pronouns function as the subject of the nonfinite noun clause when the verb is an infinitive or present participle. *Some grammars also consider the form of the noun clause in sentences like I demand that the child eat his vegetables a finite noun clause with a verb conjugated into the subjunctive mood. As Subjects Nouns clauses first function as grammatical subjects. Subjects are words, phrases, and clauses that perform the action of or act upon the verb. The following italicized noun clauses are examples of subjects: o That his daughter stole his car surprises me. o For you to not finish school now would be foolish. o What you said made the crowd angry. Both finite and nonfinite noun clauses can function as subjects. • slide 5 of 13 As Subject Complements Nouns clauses secondly function as subject complements. Subject complements are words, phrases, and clauses that follow copular verbs and describe the grammatical subject. The following italicized noun clauses are examples of subject complements: o The reason you failed the test was that you did not study the eight grammatical forms. o The thief will be whoever has blue ink on their hands. o That noise is the dog crying in his crate. Both finite and nonfinite noun clauses can function as subject complements. As Direct Objects Nouns clauses thirdly function as direct objects. Direct objects are words, phrases, and clauses that follow and receive the action of transitive verbs. The following italicized noun clauses are examples of direct objects: o Some teachers had been wondering if they chose the right career. o I would hate for you to get sick. o My son eats whatever we put on his plate. Both finite and nonfinite noun clauses can function as direct objects. As Object Complements Nouns clauses fourthly function as object complements. Object complements are words, phrases, and clauses that directly follow and describe the direct object. The following italicized noun clauses are examples of object complements: o The judges have declared the winner whoever entered the double chocolate fudge cake. o You may call my husband whatever you wish. o The assessment committee announced the problem "us refusing to try new procedures." Both finite and nonfinite noun clauses can function as object complements although nonfinite noun clauses perform the function infrequently. As Indirect Objects Nouns clauses fifthly function as indirect objects. Indirect objects are words, phrases, and clauses that indicate to or for whom or what the action of a transitive verb is performed. The following italicized noun clauses are examples of indirect objects: o The family court judge will give what the children want some consideration. o Have you given how you want to decorate the office any thought? o My classmates gave me singing the school song a gold star. Both finite and nonfinite noun clauses can function as direct objects although nonfinite noun clauses again perform the function infrequently. Prepositional Complements Nouns clauses function as prepositional complements. Prepositional complements are words, phrases, and clauses that directly follow a preposition and complete the meaning of a prepositional phrase. The following italicized noun clauses are examples of prepositional complements: o The students are thinking about what they just learned in class. o His wife listened to him singing in the shower. o My puppy begged for me to give him a treat. Both finite and nonfinite noun clauses can function as prepositional complements. Adjective Phrase Complements Nouns clauses seventhly function as adjective phrase complements. Adjective phrase complements are words, phrases, and clauses that complete the meaning of an adjective. The following italicized noun clauses are examples of adjective phrase complements: o Most English teachers would be happy that you are furthering your study of grammar. o My supervisor is worried that the roof will leak again. o I am sad that my husband is ill. Only finite noun clauses can function as adjective phrase complements. Noun Phrase Complements Noun clauses function as noun phrase complements. Noun phrase complements are words, phrases, and clauses that complete the meaning of a noun. The following italicized noun clauses are examples of noun phrase complements: o The claim that the earth is flat was once widely believed. o My problem is the fact that you are always late for work. o Our hope that peace will be achieved is possible. Only finite noun clauses that begin with the subordinating conjunction that can function as noun phrase complements. Practice Exercise Identify the noun clauses in the following sentences. Also identify the grammatical form and grammatical function of the noun clause. Sentences 21. My mom had wanted me to organize her photographs. 22. What that patron complained about is of little importance. 23. The committee will give that the students want longer library hours some thought. 24. The child is sad that she cannot have another cookie. 25. For the neighbors to sell their house would be a mistake. 26. His grandparents laughed at him sliding down the muddy hill. 27. You may invite whoever you want to the party. 28. All that commotion was the neighbors cleaning out their garage. 29. I would hate for that man to miss his bus. 30. The puppy was surprised that the cat bit his nose. Answers 31. My mom had wanted me to organize her photographs. nonfinite – direct object 32. What that patron complained about is of little importance. finite – subject 33. The committee will give that the students want longer library hours some thought. finite – indirect object 34. The child is sad that she cannot have another cookie. finite – adjective phrase complement 35. For the neighbors to sell their house would be a mistake. nonfinite – subject 36. His grandparents laughed at him sliding down the muddy hill. nonfinite – prepositional complement 37. You may invite whoever you want to the party. finite – direct object 38. All that commotion was the neighbors cleaning out their garage. nonfinite – subject complement 39. I would hate for that man to miss his bus. nonfinite – direct object 40. The puppy was surprised that the cat bit his nose. finite – adjective phrase complement • slide 13 of 13

MPDPL KOROSI DAN CARA PRNCEGAHANNYA

MAKALAH MPDPL KOROSI DAN CARA PRNCEGAHANNYA NAMA : SINGGIH AULLIYASAPUTRA KELAS : XI TEKNIK PEMESINAN 4 NO : 17 PENGERTIAN KOROSI Pengertian Korosi, Korosi adalah kerusakan atau degradasi logam akibat reaksi redoks antara suatu logam dengan berbagai zat di lingkungannya yang menghasilkan senyawa-senyawa yang tidak dikehendaki. Selain itu korosi dapat berarti penurunaan kualitas logam yang disebabkan oleh reaksi kimia suatu logam dengan unsur-unsur lain yang terdapat di alam. Penyebab, Cara Pencegahan, Proses Terjadinya, Besi, Logam, Faktor-Faktor yang Mempengaruhi, Kimia - Aplikasi lain dari prinsip elektrokimia adalah pemahaman terhadap gejala korosi pada logam dan pengendaliannya. Berdasarkan data potensial reduksi standar, diketahui bahwa logam-logam selain emas umumnya terkorosi (teroksidasi menjadi oksidanya). 1. Definisi / Pengertian Korosi Korosi pada logam terjadi akibat interaksi antara logam dan lingkungan yang bersifat korosif, yaitu lingkungan yang lembap (mengandung uap air) dan diinduksi oleh adanya gas O2, CO2, atau H2S. Korosi dapat juga terjadi akibat suhu tinggi. Korosi pada logam dapat juga dipandang sebagai proses pengembalian logam ke keadaan asalnya, yaitu bijih logam. Misalnya, korosi pada besi menjadi besi oksida atau besi karbonat. 4Fe(s) + 3O2(g) + 2nH2O(l) → 2Fe2O3.nH2O(s) Fe(s) + CO2(g) + H2O(l) → Fe2CO3(s) + H2(g) Oleh karena korosi dapat mengubah struktur dan sifat-sifat logam maka korosi cenderung merugikan. Diperkirakan sekitar 20% logam rusak akibat terkorosi pada setiap tahunnya. Logam yang terkorosi disebabkan karena logam tersebut mudah teroksidasi. Menurut tabel potensial reduksi standar, selain logam emas umumnya logam-logam memiliki potensial reduksi standar lebih rendah dari oksigen. Jika setengah reaksi reduksi logam dibalikkan (reaksi oksidasi logam) digabungkan dengan setengah reaksi reduksi gas O2 maka akan dihasilkan nilai potensial sel, Esel positif. Jadi, hampir semua logam dapat bereaksi dengan gas O2 secara spontan. Beberapa contoh logam yang dapat dioksidasi oleh oksigen ditunjukkan pada persamaan reaksi berikut. 4Fe(s) + O2(g) + 2nH2O(l) → 2Fe2O3.nH2O(s) Esel = 0,95 V Zn(s) + O2(g) + 2H2O(l) → Zn(OH)4(s) Esel = 0,60 V 2. Mekanisme / Proses Terjadinya Korosi pada Besi Oleh karena besi merupakan bahan utama untuk berbagai konstruksi maka pengendalian korosi menjadi sangat penting. Untuk dapat mengendalikan korosi tentu harus memahami bagaimana mekanisme korosi pada besi. Korosi tergolong proses elektrokimia, seperti yang ditunjukkan pada Gambar 1. Gambar 1. Proses korosi pada besi. Besi memiliki permukaan tidak halus akibat komposisi yang tidak sempurna, juga akibat perbedaan tegangan permukaan yang menimbulkan potensial pada daerah tertentu lebih tinggi dari daerah lainnya. Pada daerah anodik (daerah permukaan yang bersentuhan dengan air) terjadi pelarutan atom-atom besi disertai pelepasan elektron membentuk ion Fe2+ yang larut dalam air. Fe(s) → Fe2+(aq) + 2e– Elektron yang dilepaskan mengalir melalui besi, sebagaimana elektron mengalir melalui rangkaian luar pada sel volta menuju daerah katodik hingga terjadi reduksi gas oksigen dari udara: O2(g) + 2H2O(g) + 2e– → 4OH–(aq) Ion Fe2+ yang larut dalam tetesan air bergerak menuju daerah katodik, sebagaimana ion-ion melewati jembatan garam dalam sel volta dan bereaksi dengan ion-ion OH– membentuk Fe(OH)2. Fe(OH)2 yang terbentuk dioksidasi oleh oksigen membentuk karat. Fe2+(aq) + 4OH–(aq) → Fe(OH)2(s) 2Fe(OH)2(s) + O2(g) → Fe2O3.nH2O(s) Reaksi keseluruhan pada korosi besi adalah sebagai berikut (lihat mekanisme pada Gambar 2) : 4Fe(s) + 3O2(g) + n H2O(l) → 2Fe2O3.nH2O(s) Karat Akibat adanya migrasi ion dan elektron, karat sering terbentuk pada daerah yang agak jauh dari permukaan besi yang terkorosi (lubang). Warna pada karat beragam mulai dari warna kuning hingga cokelat merah bahkan sampai berwarna hitam. Warna ini bergantung pada jumlah molekul H2O yang terikat pada karat. Gambar 2. Mekanisme korosi pada besi. Emas dengan potensial reduksi standar 1,5 V lebih besar dibandingkan potensial reduksi standar gas O2 (1,23 V) sehingga emas tidak terkorosi di udara terbuka. Di alam emas terdapat sebagai logam murni. 3. Faktor-Faktor yang Mempengaruhi / Penyebab Korosi Berdasarkan pengetahuan tentang mekanisme korosi, Anda tentu dapat menyimpulkan faktor-faktor apa yang menyebabkan terbentuknya korosi pada logam sehingga korosi dapat dihindari. Percobaan / Praktikum Faktor-Faktor yang Dapat Menyebabkan Korosi Tujuan : Menjelaskan faktor-faktor yang dapat menyebabkan korosi. Alat : 1. Tabung reaksi 2. Paku 3. Ampelas Bahan : 1. Air 2. CaCl2 3. Oli 4. NaCl 0,5% 5. Aseton Langkah Kerja : 1. Sediakan 5 buah tabung. Masing-masing diisi dengan paku yang permukaannya sudah diampelas dan dibersihkan dengan aseton. 2. Tabung 1 diisi dengan sedikit air agar sebagian paku terendam air dan sebagian lagi bersentuhan dengan udara. 3. Tabung 2 diisi dengan udara tanpa uap air (tambahkan CaCl2 untuk menyerap uap air dari udara) dan tabung ditutup rapat. 4. Tabung 3 diisi dengan air tanpa udara terlarut, yaitu air yang sudah dididihkan dan tabung ditutup rapat. 5. Tabung 4 diisi dengan oli agar tidak ada udara maupun uap air yang masuk. 6. Tabung 5 diisi dengan sedikit larutan NaCl 0,5% (sebagian paku terendam larutan dan sebagian lagi bersentuhan dengan udara. 7. Amati perubahan yang terjadi pada paku setiap hari selama 3 hari. Pertanyaan : 1. Bagaimana kondisi paku pada setiap tabung reaksi? Pada tabung manakah paku berkarat dan tidak berkarat? 2. Apa kesimpulan Anda tentang percobaan ini? Diskusikan dengan teman sekelompok Anda. Setelah dibiarkan beberapa hari, logam besi (paku) akan terkorosi yang dibuktikan oleh terbentuknya karat (karat adalah produk dari peristiwa korosi). Korosi dapat terjadi jika ada udara (khususnya gas O2) dan air. Jika hanya ada air atau gas O2 saja, korosi tidak terjadi. Adanya garam terlarut dalam air akan mempercepat proses korosi. Hal ini disebabkan dalam larutan garam terdapat ion-ion yang membantu mempercepat hantaran ion-ion Fe2+ hasil oksidasi. Kekerasan karat meningkat dengan cepat oleh adanya garam sebab kelarutan garam meningkatkan daya hantar ion-ion oleh larutan sehingga mempercepat proses korosi. Ion-ion klorida juga membentuk senyawa kompleks yang stabil dengan ion Fe3+. Faktor ini cenderung meningkatkan kelarutan besi sehingga dapat mempercepat korosi. Macam-macam Bentuk Korosi 1. Korosi Merata (Uniform Corrosion) Korosi merata adalah korosi yang terjadi secara serentak di seluruh permukaan logam, oleh karena itu pada logam yang mengalami korosi merata akan terjadi pengurangan dimensi yang relatif besar per satuan waktu. Kerugian langsung akibat korosi merata berupa kehilangan material konstruksi, keselamatan kerja, dan pencemaran lingkungan akibat produk korosi dalam bentuk senyawa yang mencemarkan lingkungan. Sedangkan kerugian tidak langsung antara lain berupa penurunan kapasitas dan peningkatan biaya perawatan (preventive maintenance). 2. Korosi Galvanik (Galvanic Corrosion) Korosi galvanik terjadi apabila dua logam yang tidak sama dihubungkan dan berada di lingkungan korosif. Salah satu dari logam tersebut akan mengalami korosi, sementara logam lainnya akan terlindung dari serangan korosi. Logam yang mengalami korosi adalah logam yang memiliki potensial yang lebih rendah dan logam yang tidak mengalami korosi adalah logam yang memiliki potensial yang lebih tinggi. 3. Korosi Sumuran (Pitting Corrosion) Korosi sumuran adalah korosi lokal yang terjadi pada permukaan yangn terbuka akibat pecahnya lapisan pasif. Terjadinya korosi sumuran ini diawali dengan pembentukan lapisan pasif di permukaannya, pada antar muka lapisan pasif dan elektrolit terjadi penurunan pH, sehingga terjadi pelarutan lapisan pasif secara perlahan-lahan dan menyebabkan lapisan pasif pecah sehingga terjadi korosi sumuran. Korosi sumuran ini sangat berbahaya karena lokasi terjadinya sangat kecil tetapi dalam, sehingga dapat menyebabkan peralatan (struktur) patah mendadak. 4. Korosi Celah (Crevice Corrosion) Korosi celah adalah korosi lokal yang terjadi pada celah diantara dua komponen baik logam dengan non-logam maupun logam dengan logam. Mekanisme tejadinya korosi celah ini diawali dengan terjadi korosi merata diluar dan didalam celah, sehingga terjadi oksidasi logam dan reduksi oksigen. Pada suatu saat oksigen (O2) didalam celah habis, sedangkan oksigen (O2) didalam celah masih banyak, akibatnya permukaan logam yang berhubungan dengan bagian luar menjadi katoda dan permukaan logam didalam celah menjadi anoda sehingga terbentuk celah yang terkorosi. 5. Korosi Retak Tegang Korosi retak tegang terjadi karena kombinasi beban regang (tensile stress) dan koroden khusus (specific corrosive environment) yang dapat menimbulkan kerusakan awal yang kemudian menyebabkan fracture dalam logam. 6. Korosi Retak Fatik Korosi retak fatik terjadi karena kombinasi pengaruh beban dinamis (fluctuating stress) dan koroden (corrosion environment) yang dapat menyebabkan keretakan pada logam. 7. Korosi Intergranular Korosi intergranular adalah bentuk korosi yang terjadi pada paduan logam akibat terjadinya reaksi antar unsur logam di batas butirnya. Seperti yang terjadi pada baja tahan karat austenitik apabila diberi perlakuan panas. 8. Selective Leaching Selective leaching adalah korosi yang terjadi pada paduan logam karena pelarutan salah satu unsur paduan yang lebih aktif, seperti yang biasa terjadi pada paduan tembaga-seng. Mekanisme terjadinya korosi selective leaching diawali dengan terjadi pelarutan total terhadap semua unsur. Salah satu unsur pemadu yang potensialnya lebih tinggi akan terdeposisi, sedangkan unsur yang potensialnya lebih rendah akan larut ke elektrolit. Akibatnya terjadi keropos pada logam paduan tersebut. Pengukuran laju korosi dapat dilakukan dengan berbagai cara. Pengukuran yang paling sederhana biasanya dilakukan dengan cara mengukur kehilangan logam (berdasarkan perbedaan berat). Meskipun demikian beberapa metode pengukuran laju korosi yang dapat diterapkan antara lain adalah dengan mengukur ion logam yang terdapat di lingkungan, mengukur konduktivitas lingkungan, mengukur berat jenis lingkungan atau berdasarkan reaksi dengan metode elektrokimia. Begitu banyak bentuk-bentuk korosi yang dapat terjadi, oleh karena itu korosi harus dikenali dengan baik untuk dikendalikan. Sehingga diharapkan dapat meningkatkan umur (life time) peralatan yang digunakan dan dapat menghindari terjadinya akibat kegagalan material. 4. Pengendalian / Cara Pencegahan Korosi Korosi logam tidak dapat dicegah, tetapi dapat dikendalikan seminimal mungkin. Ada tiga metode umum untuk mengendalikan korosi, yaitu pelapisan (coating), proteksi katodik, dan penambahan zat inhibitor korosi. a. Metode Pelapisan (Coating) Metode pelapisan adalah suatu upaya mengendalikan korosi dengan menerapkan suatu lapisan pada permukaan logam besi. Misalnya, dengan pengecatan atau penyepuhan logam. Penyepuhan besi biasanya menggunakan logam krom atau timah. Kedua logam ini dapat membentuk lapisan oksida yang tahan terhadap karat (pasivasi) sehingga besi terlindung dari korosi. Pasivasi adalah pembentukan lapisan film permukaan dari oksida logam hasil oksidasi yang tahan terhadap korosi sehingga dapat mencegah korosi lebih lanjut. Logam seng juga digunakan untuk melapisi besi (galvanisir), tetapi seng tidak membentuk lapisan oksida seperti pada krom atau timah, melainkan berkorban demi besi. Seng adalah logam yang lebih reaktif dari besi, seperti dapat dilihat dari potensial setengah reaksi oksidasinya: Zn(s) → Zn2+(aq) + 2e– Eo = –0,44 V Fe(s) → Fe2+(g) + 2e– Eo = –0,76 V Oleh karena itu, seng akan terkorosi terlebih dahulu daripada besi. Jika pelapis seng habis maka besi akan terkorosi bahkan lebih cepat dari keadaan normal (tanpa seng). Paduan logam juga merupakan metode untuk mengendalikan korosi. Baja stainless steel terdiri atas baja karbon yang mengandung sejumlah kecil krom dan nikel. Kedua logam tersebut membentuk lapisan oksida yang mengubah potensial reduksi baja menyerupai sifat logam mulia sehingga tidak terkorosi. b. Proteksi Katodik Proteksi katodik adalah metode yang sering diterapkan untuk mengendalikan korosi besi yang dipendam dalam tanah, seperti pipa ledeng, pipa pertamina, dan tanki penyimpan BBM. Logam reaktif seperti magnesium dihubungkan dengan pipa besi. Oleh karena logam Mg merupakan reduktor yang lebih reaktif dari besi, Mg akan teroksidasi terlebih dahulu. Jika semua logam Mg sudah menjadi oksida maka besi akan terkorosi. Proteksi katodik ditunjukkan pada Gambar 3. Gambar 3. Proses katodik dengan menggunakan logam Mg. Reaksi yang terjadi dapat ditulis sebagai berikut. Anode : 2Mg(s) → 2Mg2+(aq) + 4e– Katode : O2(g) + 2H2O(l) + 4e– → 4OH–(aq) Reaksi : 2Mg(s) + O2(g) + 2H2O → 2Mg(OH)2(s) Oleh sebab itu, logam magnesium harus selalu diganti dengan yang baru dan selalu diperiksa agar jangan sampai habis karena berubah menjadi hidroksidanya. c. Penambahan Inhibitor Inhibitor adalah zat kimia yang ditambahkan ke dalam suatu lingkungan korosif dengan kadar sangat kecil (ukuran ppm) guna mengendalikan korosi. Inhibitor korosi dapat dikelompokkan berdasarkan mekanisme pengendaliannya, yaitu inhibitor anodik, inhibitor katodik, inhibitor campuran, dan inhibitor teradsorpsi. 1) Inhibitor anodik Inhibitor anodik adalah senyawa kimia yang mengendalikan korosi dengan cara menghambat transfer ion-ion logam ke dalam air. Contoh inhibitor anodik yang banyak digunakan adalah senyawa kromat dan senyawa molibdat. 2) Inhibitor katodik Inhibitor katodik adalah senyawa kimia yang mengendalikan korosi dengan cara menghambat salah satu tahap dari proses katodik, misalnya penangkapan gas oksigen (oxygen scavenger) atau pengikatan ion-ion hidrogen. Contoh inhibitor katodik adalah hidrazin, tannin, dan garam sulfit. 3) Inhibitor campuran Inhibitor campuran mengendalikan korosi dengan cara menghambat proses di katodik dan anodik secara bersamaan. Pada umumnya inhibitor komersial berfungsi ganda, yaitu sebagai inhibitor katodik dan anodik. Contoh inhibitor jenis ini adalah senyawa silikat, molibdat, dan fosfat. 4) Inhibitor teradsorpsi Inhibitor teradsorpsi umumnya senyawa organik yang dapat mengisolasi permukaan logam dari lingkungan korosif dengan cara membentuk film tipis yang teradsorpsi pada permukaan logam. Contoh jenis inhibitor ini adalah merkaptobenzotiazol dan 1,3,5,7–tetraaza–adamantane. SOAL: 1. Sebutkan pengertian korosi! 2. Apa itu pengertian prinsip elektrokimia? 3. Sebutkan pengertian Lingkungan yang bersifat korosif! 4. Sebutkan 4 macam bentuk korosi! 5. Apa itu metode pelapisan? Jawaban: 1. korosi adalah kerusakan atau degradasi logam akibat reaksi redoks antara suatu logam dengan berbagai zat di lingkungannya yang menghasilkan senyawa-senyawa yang tidak dikehendaki. Selain itu korosi dapat berarti penurunaan kualitas logam yang disebabkan oleh reaksi kimia suatu logam dengan unsur-unsur lain yang terdapat di alam. 2. prinsip elektrokimia adalah pemahaman terhadap gejala korosi pada logam dan pengendaliannya. 3. lingkungan yang bersifat korosif, yaitu lingkungan yang lembap (mengandung uap air) dan diinduksi oleh adanya gas O2, CO2, atau H2S. 4. Korosi Celah (Crevice Corrosion), Korosi Galvanik (Galvanic Corrosion), Korosi Sumuran (Pitting Corrosion), Korosi Merata (Uniform Corrosion) 5. Metode pelapisan adalah suatu upaya mengendalikan korosi dengan menerapkan suatu lapisan pada permukaan logam besi. DAFTAR PUSTAKA: http://www.planetkimia.com/2012/11/korosi/ http://kimia123sma.wordpress.com/2010/04/20/korosi-dan-cara-pencegahannya/ https://www.google.com/search?q=makalah+korosi+dan+pencegahannya&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:id:official&client=firefox-a

PERSONAL LETTERS

PERSONAL LETTERS A letter is a written message containing information from one party to another.[1] The role of letters in communication has changed significantly since the nineteenth century. Historically, letters (in paper form) were the only reliable means of communication between two people in different locations. The study of letter writing Due to the timelessness and universality of letter writing, there is a wealth of letters and instructional materials (for example, manuals, as in the medieval ars dictaminis) on letter writing throughout history. The study of letter writing usually involves both the study of rhetoric and grammar.[2] Advantages Letters are still used, particularly by law firms and businesses, for official (public) notifications, sometimes advertising. This is because of three main advantages: • No special device needed - almost everybody has a residence or other place at which he or she can receive mail. A mailbox is all that the intended recipient needs - unlike e-mail or phone calls, where the intended recipient needs access to a computer and an e-mail account or a telephone respectively. • "Catch-all" advertising- unlike e-mails, where the recipient needs an individual e-mail address to receive messages, individuals are not necessarily chosen, by rather can widely cover many or all addresses in a given locality. • Physical record - important messages that need to be retained (e.g. invoices; government notification such as tax or immigration) can be kept relatively easily and securely. The letter-delivering process Here is how a letter gets from the sender to the recipient: 1. Sender writes letter and places it in an envelope on which the recipient's address is written in the centre front of the envelope. Sender ensures that the recipient's address includes the Zip or Postal (if applicable) code and often he includes his return address on the envelope. 2. Sender buys a postage stamp and attaches it to the front of the envelope on the top right corner on the front of the envelope. 3. Sender puts the letter in a postbox. 4. The national postal service for the sender's country (e.g., the Royal Mail, UK; US Postal Service, US; Australia Post in Australia; or Canada Post in Canada) empties the postbox and takes all the contents to the regional sorting office. 5. The sorting office then sorts each letter by address and postcode and delivers the letters destined for a particular area to that area's post office. Letters addressed to a different region are sent to that region's sorting office, to be sorted further. 6. The local post office dispatches the letters to their delivery personnel who deliver them to the appropriate addresses. This whole process, depending on how far the sender is from the recipient, can take anywhere from a day to 3–4 weeks. International mail is sent via trains and airplanes to other countries Letter layout United Kingdom, Canada, and Australia The following is a common way to set out a letter: Sender's address here 24 Lambert Street Stoke-on-Trent ST4 4WE Date here Formal: 24 October 2013 Informal: October 24 Recipient's name and address here Mr Joseph Bloggs 25 Lambkin Street Stoke-on-Trent ST3 9WR Main body Formal: Dear Sir or Madam, Acquaintance: Dear Mr Johnson, Informal: Dear Boris, Content Formal: Yours faithfully, Acquaintance: Yours sincerely, Informal: Best wishes, Sender's Name Formal: Sender's Occupation and Enclosures Informal: Nothing (optional: P.S. / Post Scriptum = Afterthought) United States The following is the modified block format for a business letter, common in the United States: October 24, 2013 Your Street Address Your City, State, ZIP Mr Jack Brough 25 First Street Anytown, VA 10005 Dear Mr. Brough: This is an example of a modified block letter. The difference between it and a full block letter style is that the date begins at the center point of the page; therefore, if a letter has a 6 inch line of type, the date begins approximately over 3 inches from the left margin. The closing block also begins half-way across the page. The complimentary close and the keyed signature (first and last name of the writer) begin at the same point as the date - approximately 3 inches from the left margin. Sincerely, Robert Hayward Sales Representative Contoh Personal Letter Bogor, 6th December 2013 Dear Singgih, Hello! How are you? I hope you are fine like me. Next week, after final test, I’m planning to go your city but I don’t know where your home is. So, I will you take me at Tugu Station 2 a.m we will meet a front of area park. I’m going to wear blue shirt, and black jeans. If you are difficul to find me you can call me, maybe? This is my number 085878768844. I want to you bring me go to MALIOBORO and to try traditional foods like a gudek, etc. You don’t have to reply my letter, because you can call me or sms. Okay? I’am really impatient to go there. See you there! Love, LABIB CURRICULUM VITAE A curriculum vitae (CV) provides an overview of a person's experience and other qualifications. In some countries, a CV is typically the first item that a potential employer encounters regarding the job seeker and is typically used to screen applicants, often followed by an interview, when seeking employment. What's the difference between a resume and a CV? The primary differences are the length, the content and the purpose. A resume is a one or two page summary of your skills, experience and education. A goal of resume writing is to be brief and concise since, at best, the resume reader will spend a minute or so reviewing your qualifications. A Curriculum Vitae, commonly referred to as CV, is a longer (two or more pages), more detailed synopsis. It includes a summary of your educational and academic backgrounds as well as teaching and research experience, publications, presentations, awards, honors, affiliations and other details. When to Use a CV In the United States a Curriculum Vitae is used primarily when applying for international, academic, education, scientific or research positions or when applying for fellowships or grants. As with a resume, you may need different versions of a CV for different type of positions. What to Include in Your CV Like a resume, your CV should include your name, contact information, education, skills and experience. In addition to the basics, a CV includes research and teaching experience, publications, grants and fellowships, professional associations and licenses, awards and other information relevant to the position you are applying for. Start by making a list of all your background information, then organize it into categories. Make sure you include dates on all the publications you include. How to Write a Curriculum Vitae Do you need help writing a curriculum vitae? Before you start, review these tips so you can include the appropriate information in your curriculum vitae (CV) and format your curriculum vitae correctly. Remember, the first impression is the one that matters, so, your CV needs to be perfect! Curriculum Vitae LIVING HISTORY LIST PERSONAL DATA Name : Justin Bieber Son Gender : Male Place , date of birth : Jakarta , January 1, 1980 Citizenship : Indonesia Relationship Status : Never married Height , weight : 170 cm , 61 kg Health : Very good Religion : Islam Address : Jl . No. Melinda Dee . 1 South Jakarta Phones , Mobile: 085 238 111 888 E - mail : jb_putra@yahoo.com EDUCATION » Formal 1985 - 1991 : SDN 1 Bandung 1991 - 1994 : SMP 2 Bandung 1994 - 1997 : SMAN 1 Bandung 1997 - 2001 : Undergraduate Program ( S - 1 ) Accounting , University of Pancasila , Jakarta » Non-Formal 1998 - 1999 : Computer and Internet Courses in Puskom Gilland Ganesha , Jakarta 1999 - 2002 : English course in IALF Denpasar , Bali 2004 - 2004 : Tax Course ( Brevet A & B ) in FAIUP , Jakarta EXPERIENCE ORGANIZATION Student Council SMU 1 Bandung Period 1995-1996 Chairman of the Sub - Division of Academic Student Council 1996-1997 period Accounting Students Association members Pancasila University 2000-2001 period Head of Department of Accounting 2 HIMA 1999-2000 period ABILITY Accounting and Administration capabilities ( Journal Printing & Calculation , Ledger , Petty Cash Payroll & Calculation , Inventory Controls , Project Data Updating , Teller , Salary Caldulation ) . Taxation system . Computer capability ( MS Word , MS Excel , MS Power Point , MS Access , MS Outlook ) . Internet capabilities . WORK EXPERIENCE Working at PT . Bersemi Jaya Bali , Bali Period : January 2009 - June 2012 Status : Permanent Employee Position : Staff Accounting and Taxation Example LIVING HISTORY LIST PERSONAL DATA Name: Singgih aulliya saputra Gender: Male Place, date of birth: Sleman, 23 april 1997 Citizenship: Indonesia Relationship Status: Never married Height, weight: 160 cm, 41 kg Health: Very good Religion: Islam Address: Nusupan, Trihanggo, Limestone, Sleman Phones, Mobile: 085 878 768 844 E-mail: singgihpertamaputra@yahoo.com EDUCATION »Formal 2002 - 2003: TK IT Jabal NUR 2003 - 2009: SDN 2 vigil 2009 - 2012: SMP N 7 Yogyakarta 2012 - 2015: SMK N 2 Yogyakarta »Non-Formal 2007 - 2009: Les Saint in KHARISMA SAINT ABILITY Mechanical machining capabilities. Computer capability (MS Word, MS Excel, MS Power Point, MS Access, MS Outlook). Internet capabilities. Memorandum From Wikipedia, the free encyclopedia Jump to: navigation, search "Memoranda" redirects here. For the open source personal information manager software, see Memoranda (software). For the documentary of the same name, see Memorandum (film). For the record label, see Memorandum Recordings. A memorandum (abbrev.: memo) was from the Latin verbal phrase memorandum est, the gerundive form of the verb memoro, "to mention, call to mind, recount, relate",[1] which means "It must be remembered (that)...". It is therefore a note, document or other communication that helps the memory by recording events or observations on a topic, such as may be used in a business office. The plural form of the Latin noun memorandum so derived is properly memoranda, but if the word is deemed to have become a word of the English language, the plural memorandums, abbreviated to memos, may be used. (See also Agenda, Corrigenda, Addenda) A memorandum can have only a certain amount of formats, it may have a format specific to an office or institution. In law specifically, a memorandum is a record of the terms of a transaction or contract, such as a policy memo, memorandum of understanding, memorandum of agreement, or memorandum of association. Alternative formats include memos, briefing notes, reports, letters or binders. They could be one page long or many. If the user is a cabinet minister or a senior executive, the format might be rigidly defined and limited to one or two pages. If the user is a colleague, the format is usually much more flexible. At its most basic level, a memorandum can be a handwritten note to one's supervisor. In business, a memo is typically used by firms for internal communication, as opposed to letters which are typically for external communication.[2] Dean Acheson famously quipped that "A memorandum is not written to inform the reader but to protect the writer". Charles Peters wrote that "bureaucrats write memoranda both because they appear to be busy when they are writing and because the memos, once written, immediately become proof that they were busy."[3] Example To: septi harsoyo From: singgih aulliya Subject: borrow books I have a test tomorrow. I do not have the book. help you bring the book tomorrow. for I borrowed. thank a lot