MAPEL KIMIA BAB 7 Tata nama senyawa kimia

 

TATA NAMA SENYAWA BINER

1.         RUMUS KIMIA

Rumus kimia merupakan kumpulan lambang atom dengan aturan tertentu. Misalnya, rumus air adalah H₂O dan garam dapur (natrium klorida) adalah NaCl. Jumlah tiap atom pada rumus kimia ditulis sebagai angka indeks. Pada rumus kimia air (H₂O), angka indeks H adalah 2 dan angka indeks O adalah 1 (angka indeks I tidak perlu ditulis). Adapun pada rumus kimia garam dapur (NaCI), angka indeks kedua atom adalah 1 sehingga tidak perlu ditulis. Rumus kimia suatu zat adalah khas. Kekhasan itu ditentukan oleh daya ikat dan bilangan oksidasi yang dimiliki suatu atom.

1. a.        Daya Ikat Atom

Daya ikat atom adalah kemampuan suatu atom untuk mengikat atom lain sehingga membentuk suatu molekul. Daya ikat atom juga disebut valensi. Tiap atom mempunyai daya ikat tertentu.

Untuk memahami daya ikat atom, perhatikan senyawa HCI, H₂O, NH₃, SO₂, SO₃, dan CH. Ternyata, Cl mengikat 1 atom H, O mengikat 2 atom H, N mengikat 3 atom H, S mengikat 2 atau 3 atom O, dan C mengikat 4 atom H. Karena mempunyai daya ikat paling kecil, atom H dijadikan pembanding dan ditetapkan memiliki valensi 1. Oleh karena itu, valensi atom CI adalah 1, valensi atom O adalah 2, valensi atom N adalah 3, valensi atom S adalah 4 atau 6, dan valensi atom C adalah 4.

b.        Tata Nama Senyawa Biner

Senyawa biner adalah kimia yang hanya terbentuk dari dua unsur. Unsur yang terbentuk tersebut dapat terdiri atas unsur logam dan bukan logam atau keduanya terdiri atas unsur bukan loga

Jika senyawa biner terdiri atas unsur logam dan bukan logam, aturan penamaan senyawanya sebagai berikut.

Nama unsur logam disebutkan lebih dahulu, kemudian diikuti nama unsur bukan logam yang diakhiri dengan akhiran –ida.

Contoh :

NaCl = Natrium klorida         MgBr₂=Magnesium bromida

Na adalah unsur logam       Mg adalah unsur logam

Cl adalah unsur non logam         Br adalah unsur non logam

Senyawa ionik walaupun tersusun atas ion positif dan negatif, tetapi secara keseluruhan bersifat netral, sehingga muatan totalnya adalah nol. Ini berarti satu Na⁺ akan bergabung dengan satu Cl^– dalam NaCl dan satu Mg²⁺ bergabung dengan dua Br^– dalam MgBr₂ demikian seterusnya. Berikut ini contoh pemberian nama dan simbol senyawa sederhana :

SENYAWA	NAMA SENYAWA	SENYAWA	NAMA SENYAWA
Li2O	Litium oksida	CaO	Kalsium oksida
NaBr	Natrium bromida	SrO	Stronsium oksida
KCl	Kalium klorida	BaCl2	Barium klorida
Rb2O	Rubidium oksida	Al2O3	Aluminium oksida
CsI	Cesium iodida	ZnO	Seng oksida
MgCl	Magnesium klorida	AgCl	Perak klorida

1. 2.         Jika senyawa biner terdiri atas unsur bukan logam dan bukan logam, aturan penamaan senyawanya sebagai berikut.

Nama unsur bukan logam yang kelelektronegatifannya lebih rendah disebutkan lebih dahulu, kemudian diikuti nama unsur bukan logam yang lain dan diakhiri dengan akhiran –ida. Senyawa yang terbentuk antara unsur bukan logam dan bukan logam merupakan senyawa yang berikatan kovalen. Jumlah atom yang dimiliki oleh senyawa biner disebutkan dengan cara memberi awalan bahasa Latin sebagai berikut :

1     =     mono           6     =   heksa

2     =     di                  7     =   hepta

3     =     tri                  8     =   okta

4     =     tetra              9     =   nona

5     =     penta           10   =   deka

Awalan bahasa Latin mono tidak diletakkan pada nama unsur non logam yang pertama melainkan pada unsur nonlogam kedua. Awalan bahasa latin dari nama logam pertama disebutkan mulai dari yang berjumlah 2, dst. Contoh :

N₂O         =     dinitrogen monoksida

NO           =     nitrogen monoksida

N₂O₃        =     dinitrogen trioksida

NO₂         =     nitrogen dioksida

N₂O₅        =     dinitrogen pentaoksida

CCl₄        =     karbon tetraklorida

CO           =     karbon monoksida

CO₂         =     karbon dioksida

Unsur-unsur logam dengan bilangan oksidasi lebih dari satu jenis, maka bilangan oksidasinya ditulis dengan angka romawi

Sebelumnya harus dipahami pengertian dan cara menentukan bilangan oksidasi. Bilangan oksidasi menyatakan jumlah elektron yang terlibat pembentukan ikatan.

Jika melepaskan elektron, suatu atom memiIiki bilangan oksidasi positif. Sebaliknya, jika menangkap elektron, suatu atom memiliki bilangan oksidasi negatif. Pengertian bilangan oksidasi seperti itu berlaku untuk molekul ionik. Jika demikian, bagaimana bilangan oksidasi untuk molekul kovalen?

Molekul kovalen dibedakan atas molekul kovalen polar dan nonpolar. Untuk molekul kovalen polar, atom yang lebih elektronegatif dianggap bermuatan negatif dan molekul yang lain dianggap bermuatan positif. Adapun untuk molekul kovalen nonpolar, bilangan oksidasinya sama dengan nol.

Aturan bilangan oksidasi (biloks) adalah sebagai berikut :

1. Bilangan oksidasi unsur bebas (monoatomik, diatomik, atau poliatomik) sama dengan 0 (nol). Misalnya : bilangan oksidasi Na, Mg, Fe, O, Cl₂, H₂, P₄ dan S₈ = 0
2. Bilangan oksidasi unsur H dalam senyawa = +1, kecuali pada senyawa hidrida =  –1 (misalnya : NaH)
3. Bilangan oksidasi unsur O dalam senywa = –2, kecuali pada senyawa peroksida = –1  (misalnya : Na₂O₂, H₂O₂, BaO₂), dan pada senyawa oksifluorida (OF₂) = +2
4. Bilangan oksidasi unsur logam dalam senyawa selalu positif dan nilainya sama dengan valensi logam tersebut. ( Misalnya : Biloks logam gol.IA= +1, gol.IIA=+2, gol.IIIA=+3)
5. Bilangan oksidasi unsur golongan VIIA dalam senyawa = –1
6. Bilangan oksidasi unsur dalam bentuk ion tunggal sama dengan muatannya. (Misalnya Biloks Na pada Na⁺= +1, Cl pada Cl^–=–1, Mg pada Mg²⁺=+2)
7. Jumlah bilangan oksidasi unsur-unsur dalam suatu senyawa sama dengan 0 (nol), Misalnya :

Biloks S pada H₂SO₄ ditentukan dengan cara :

H₂SO₄     =     0

( 2 x biloks H) + S + (4 x biloks O)     =     0

( 2 X 1) + S + (4 X (-2) )     =     0

2 + S – 8     =     0

S     =     8 – 2

S     =     +6

1. Jumlah bilangan oksidasi unsur-unsur dalam suatu ion poliatom sama dengan muatannya.

Misalnya :

Biloks Cr pada Cr₂O₇^2-

Cr₂O₇^2-     =   –2

Cr₂ + ( 7 x biloks O )     =   –2

Cr₂ + ( 7 x (-2) )     =   –2

Cr₂ – 14     =   –2

Cr₂     =   14 – 2

Cr     =   12 / 2

Cr     =   +6

Contoh 1.

Senyawa CrO diberi nama dengan aturan sebagai berikut :

1. Mencari biloks Cr pada CrO, dengan cara :

CrO  =     0

Cr + (1 x biloks O)  =     0

Cr + ( 1 x (-2))  =     0

Cr + (-2)  =     0

Cr – 2  =     0

Cr  =     2

Maka biloks Cr pada CrO  =     2

1. Biloks Cr ditulis dengan angka Romawi setelah nama logam dalam bahasa Indonesia, dilanjutkan nama nonlogam dan diakhiri dengan akhiran –ida. Sehingga nama senyawa CrO adalah Kromium (II) oksida

Contoh 2.

Senyawa FeF₃ diberi nama dengan aturan sebagai berikut :

1. Mencari biloks Fe pada FeF₃, dengan cara :

FeF₃  =     0

Fe + (3 x biloks F)  =     0

Fe + ( 3 x (-1))  =     0

Fe + (-3)  =     0

Fe – 3  =     0

Fe  =     3

Maka biloks Fe pada FeF₃  =     3

1. Biloks Fe ditulis dengan angka Romawi setelah nama logam dalam bahasa Indonesia, dilanjutkan nama nonlogam dan diakhiri dengan akhiran –ida. Sehingga nama senyawa FeF₃ adalah Besi (III) florida

MAPEL ENGLISH LM BAB 9 A hortatory exposition text

 A Hortatory Exposition Text

Objectives

• Learners are able to comprehend the information given on the text.
• Learners are able to understand the aim of a hortatory exposition text.

Learn about it!

What is a Hortatory Text

Hortatory exposition text is a text containing arguments or reasons of the writers in order to persuade the readers. It tells the reader what they should or should not do about a particular case.

What is the function of hortatory exposition texts?

Answer: to persuade the reader or listener about something which should or should not be the case.

Generic structure of hortatory exposition texts

1. Thesis statement: The announcement of issue.
2. Arguments: Reasons for concern that lead to recommendation.
3. Recommendation: Statement of what should or should not to happen

Characteristics of hortatory exposition texts

1. Focusing on the writer.
2. Using action verb: eg. run, jump, kick, eat, cry, break, smile, walk, drink, talk.
3. Using adverb: eg. Surely, certainly.
4. Using modals: eg. May, can, could, will.
5. Using temporal connectives: eg. Firstly, secondly, however, therefore, etc.
6. Using evaluative words: eg. Important, trustworthy, valuable.
7. Using simple present tense.
8. Using passive voice.

Do you understand?

Listen to the following example of a hortatory exposition text.

Students and Their Cellphones

Cellphones or mobile phones has become obligatory things to be brought by people nowadays. The reason behind it is the use of cellphones is not only for communication, but also for several things. Today’s cellphones can be used for taking pictures, taking videos, listening to the music, recording voice, storing documents, and playing games. Therefore, most of people use cellphone as their mobile storage devices. Adult, teenagers, children, working people, or students have cellphone in their pocket. However should the students be allowed or be banned to bring cellphones to their school?

Nowadays many students bring cellphones to their school. Many schools allow their students to bring cellphones so their students can communicate with their parents easily. But some other schools ban the use of cellphones at school. It is quite reasonable since bringing cellphones to school may cause several disturbance in the teaching and learning process. Many students who bring cellphone use it irresponsibly during the learning activities. For example, they use cellphone for listening to the music during the learning activities. Some others use it to chat with other students. Some girls use the front camera to take selfie when their teacher are explaining learning materials. Those use of cellphones will distract the students’ concentration.

Besides using cellphone during learning activities, the students may use cellphone as a media for cheating. Many students use cellphone to text their friends during the examination. The students may also see their learning notes in their cellphone during
examination. Therefore, many schools should make a strict rule for students who bring cellphones to their school. For example, all cellphones should be turned off or should be switched into vibrated mode during the learning process. If a student has to answer a call during the learning process, she or he has to get permission from the teacher and pick the phone outside the classroom. When doing examination, all the students have to turn off their cellphone. Their teacher may also collect all cellphones during the examination. From the aforementioned explanation, the students need to use cellphone wisely so cellphone will not become disturbance during the learning activities or during the examination.

After listening to the example of a hortatory exposition text, now pay attention to the following explanation:

1. The recording was started by an issue whether the use of cellphones at school should be banned or not. This issue is the example of a thesis statement of a hortatory exposition text.
2. After that, the speaker proposed several arguments related to the issue. The first argument is that the use of cellphones can distract students’ concentration if the students use cellphones in the classroom.
3. The second argument is that cellphones can distract students’ concentration during final examinations.
4. Finally, in the end of the recording, the speaker proposed several recommendations related to the problem explained before.

Writing an Argument Essay

Objectives

Understanding how to write an argument essay in context daily life

·         Able to construct the outline of an argument essay

·         To know how to developing the outline of an argument essay

·         Able to link one paragraph to another paragraph

·         Able to create an argument essay.

Learn about it!

Previous meeting we have learned how to make an opinion and facts. To make an opinion we can use phrases such as in my opinion …., in my view …., in my mind …, it is believed that …and use the modal verbs such as might, should, could, and ought to. We can use our opinion in our argument. Argument is reason or reasons why you support or oppose an idea or action.

            Argument can be presented in form of spoken or written. In this occasion I would like to introduce how to present an argument in form of an essay. Essay is group of paragraph which has link one paragraph to another paragraph. Paragraph is group of sentences which develop topic sentence. Sentence is group of words which stand up of at least subject and predicate.

            Writing an essay we should follow some steps of writing such as drafting, rough draft, proof reading, revising and publishing. Drafting can be done by several strategy such as mind mapping, listing or charting. Rough draft is done after doing drafting to develop the sentences to make some paragraph writing. Proof reading is done to make sure that the essay has good quality in term of mechanic, content, and organization of paragraph, grammar, unity and coherence. You can do proof reading by yourself or your peer. After getting feedback of your writing you continue to revising step and publishing your essay.

1.             Drafting

In this essay I will use listing to develop my essay.

INTRODUCTION

·         Background sentence: Muhajir Effendy release full day school program

·         Detail background: Full day school program is the extended school hour starting form 8 to 4 pm

·         Thesis: I agree with full day school program (it is believed that full day school should be supported)

·         Transition Sentence: there are two reasons which would be discussed in this order

SUPPORTING PARAGRAPH 1 (reason 1)

·         Topic sentence

·         Supporting sentence

·         Developing sentence

·         Conclusion

SUPPORTING PARAGRAPH 2 (reason 2)

·         Topic sentence

·         Supporting sentence

·         Developing sentence

·         Conclusion

CONCLUDING PARAGRAPH

·         Summary

·         Restatement of thesis/reiteration

·         Recommendation

2.             Rough draft

3.             Proof Reading

4.             Revising

5.             Publising

Do you understand?

Lets practice!

The presence of technology in the classroom has become more and more apparent and offers students tremendous resources with which to supplement their education. Given time, technology will completely replace the conventional teachers in the classroom. Do you agree or disagree with this statement?

Before writing an essay we should determine the scope of discussion. The scope of the statement above are:Technology/////Classroom/////Teachers////Students////

So we may not discuss the topic out of the scope of discussion above. The statement above asking whether we agree or disagree with the statement. I would like to oppose this statement. So I will make disagree essay. There are some topic that I presented such as:

1.      The teacher can cater the need of the students (technology cannot do this)

2.      Teacher can give motivation and discipline to the students (technology cannot do this)

3.      Teacher can include the current news and personal stories. (technology cannot do this)

From the statement above we can make our argument essay by following the writing steps. First you should do drafting. In this occasion I will use listing. From three topic stating above I select two of them. They are no 1 and 2

INTRODUCTION

·         Background

·         Detail background

·         Thesis

Today, technology has become more and more apparent and offers the students tremendous resourches in teaching learning process. We can find a lot of information by using technology such as computerize in education which supported by internet. It is disagreed that technology will replace the conventional teachers. It is proven by the teachers can cater the students need and also give the discipline and moral value in teaching learning process but technology cannot do this.

SUPPORTING PARAGRAPH 1

·         Topic

·         Example

·         Discussion

·         Conclution

Teachers can replace their approaching or technique in teaching when the students feel difficulties in understanding the topic given. As an example, when students are having trouble in memorizing the irregular verb in English, the teacher can use game strategy in teaching or the other fun technique. Computerize cannot paraphrase the topic given or changing the approach and the technique in learning  topic of the classroom. Technology cannot replace the conventional teachers in teaching and learning.

SUPPORTING PARAGRAPH 2

·         Topic

·         Example

·         Discussion

·         Conclution

Teachers in teaching not only tranfer knowledge and train the students skill bur also improve students’ attitude such as discipline and moral value.As an example, Teacher could give the reward or punishment to the students. When student made mistake like not making homework, she/he is given punishment to make her/him more discipline. Computerize in education cannot do the reward and punishment approaching in which believed that improve the students quality on their attitude.Technology cannot replace the conventional teachers.

CONCLUDING PARAGRAPH

·         Summary

·         Restatement of thesis

·         Recommendation

The presence of technology in education is very essential because it can be knowledge resources in fulfill the students need. However, Technology in form of Computerize or others in education cannot replace the existence of the teachers in the classroom. Such the above explanation, teachers can cater the students need and give moral value and discipline but not for the technology. It is recommended that technology and teachers are two aspect that cannot be separated. Teachers use technology as media in teaching and learning to improve students’ quality in education.

2. Rough Draft of Argument Essay

Today, technology has become more and more apparent and offers the students tremendous resourches in teaching learning process. We can find a lot of information by using technology such as computerize in education which supported by internet. It is disagreed that technology will replace the conventional teachers. It is proven by the teachers can cater the students need and also give the discipline and moral value in teaching learning process but technology cannot do this.

Teachers can replace their approaching or technique in teaching when the students feel difficulties in understanding the topic given. As an example, when students are having trouble in memorizing the irregular verb in English, the teacher can use game strategy in teaching or the other fun technique. Computerize cannot paraphrase the topic given or changing the approach and the technique in learning  topic of the classroom. Technology cannot replace the conventional teachers in teaching and learning.

Teachers in teaching not only tranfer knowledge and train the students skill bur also improve students’ attitude such as discipline and moral value.As an example, Teacher could give the reward or punishment to the students. When student made mistake like not making homework, she/he is given punishment to make her/him more discipline. Computerize in education cannot do the reward and punishment approaching in which believed that improve the students quality on their attitude.Technology cannot replace the conventional teachers.

The presence of technology in education is very essential because it can be knowledge resources in fulfill the students need. However, Technology in form of Computerize or others in education cannot replace the existence of the teachers in the classroom. Such the above explanations, teachers can cater the students need and give moral value and discipline but not for the technology. It is recommended that technology and teachers are two aspect that cannot be separated. Teachers use technology as media in teaching and learning to improve students’ quality in education.

The above essay is in form of rough draft, you can make this essay better by doing proof reading and revising it before publishing to the readers. That all for today don’t forget to study English and good bye.

Keypoints

1.             There are two ways in stating the opinion. They are

·         Phrases (I think …; In my opinion …; It is believed …)

·         Modal verbs (should…; could…; might….; would…)

2.             Steps of writing are

·         Drafting

a.       Listing

b.      Mind Mapping

c.       Charting

·         Rough draft

·         Proof reading

·         Revising

·         Publishing

3.             Listing can be presented as follow

INTRODUCTION

·         Background

·         Detail background

·         Thesis

SUPPORTING PARAGRAPH 1

·         Topic

·         Example

·         Discussion

·         Conclusion

SUPPORTING PARAGRAPH 2

·         Topic

·         Example

·         Discussion

·         Conclusion

CONCLUDING PARAGRAPH

·         Summary

·         Restatement of thesis

·         Recommendation

4.             Make sure with the content, organization, grammar, and mechanic on your writing.