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Rabu, 03 Februari 2021

MAPEL KIMIA BAB 5 Benzena dan turunannya

 

Benzena dan Turunannya: Pengertian, Rumus, Soal


Pernahkah kamu mencium bau wangi kapur barus dari lemarimu?

Senyawa apa yang sebenarnya terkandung dalamnya sehingga dapat menghasilkan aroma yang khas tersebut?

Ya, senyawa tersebut mengandung hidrokarbon aromatik, yaitu senyawa turunan benzena. Begitu banyak senyawa turunan benzena kita temui sehari-hari.

Bagaimana struktur, tata nama, dan kegunaan benzena dan turunannya? Marilah kita pelajari lebih lanjut agar lebih jelas.

Pengertian Benzena

Benzena merupakan senyawa hidrokarbon aromatik paling sederhana dengan rumus molekul C6H6 yang berbentuk siklik (membentuk cincin).

Benzena memiliki satu atom H yang terikat di setiap atom C dan memiliki total 3 buah ikatan rangkap dua yang berselang-seling.

Terdapat dua jenis cara menggambar struktur benzena yaitu dengan struktur Kekule dan struktur delokalisasi π.

Benzena

Struktur Kekule dikemukakan oleh Kekule pada tahun 1865.

Kekule menyatakan bahwa 6 atom karbon benzena berada pada sudut-sudut yang membentuk heksagon beraturan dengan satu atom hidrogen mengikat pada setiap atom karbon dengan ikatan tunggal dan ikatan ganda berseling.

Pada struktur delokalisasi π, ikatan rangkap pada benzena digambarkan sebagai lingkaran yang menyatakan terjadinya delokalisasi ikatan π.

Delokalisasi ini terjadi karena elektron pada ikatan rangkap yang berseling itu tersebar di seluruh cincin.

Mengapa kita perlu mempelajari benzena sedangkan strukturnya hanyalah sangat sederhana?

Meskipun benzena hanyalah cincin aromatik dengan enam atom karbon, pada kenyataan senyawa ini banyak kita temui sehari-hari.

Senyawa benzena memiliki berbagai turunan senyawa. Apa saja turunan senyawa benzena itu? Mari kita bahas lebih lanjut.

Senyawa Turunan Benzena dan Tata Namanya

Dari banyak turunan senyawa benzena yang ada, terdapat tiga jenis penggolongan senyawa benzena, yaitu benzena monosubstitusi, benzena disubstitusi, dan benzena substitusi lebih dari dua.

Benzena monosubstitusi merupakan benzena dengan satu substituen yang menggantikan salah satu atom H. Benzena jenis ini memiliki tata nama “nama substituen + benzena”. Perhatikan contoh berikut.

Turunan Benzena

Nama-nama substituen yang umum terdapat pada senyawa benzena antara lain:

Nama SubstituenRumus/Struktur Kimia
nitro-NO2
floro-F
kloro-Cl
bromo-Br
isopropil-CH(CH3)2
hidroksi-OH

Benzena disubstitusi memiliki dua substituen sehingga dapat terjadi isomer posisi. Untuk membedakan isomer posisi pada benzena disubstusi, digunakan penamaan orto (o), meta (m), para (p).

Orto digunakan apabila substituen berada pada atom C nomor 1 dan 2. Meta digunakan apabila substituen berada pada atom C nomor 1 dan 3. Sedangkan para digunakan apabila substituen berada pada atom C nomor 1 dan 4.

Penomoran tentunya memperhatikan substituen terdekat sehingga tidak ada 1 dan 5 melainkan pada nomor 1 dan 3. Untuk lebih jelasnya perhatikan contoh berikut.

Turunan Benzena 2

Bagaimana jika substituennya berbeda?

Apabila substituennya berbeda maka salah satu substituen menjadi senyawa utama sedangkan yang lain menjadi cabangnya.

Pemilhan senyawa utama memperhatikan aturan dibawah ini, dimana senyawa yang lebih diprioritaskan menjadi senyawa utama.


(lebih prioritas) –COOH, –SO3, –CH3, –CN, –OH, –NH2, –R, –NO2, –X

Senyawa Benzena

Nama-nama senyawa dengan substituen tersebut sebagai berikut.

Benzena dengan substituenNama senyawa
–COOHAsam benzoat
–COOBenzoat
–SO3Sulfonat
–SO3HAsam Sulfonat
–CH3Toluena
–CNBenzonitril
–OHFenol
–NH2Fenilamin
–NO2Nitrobenzene

Nah, lalu bagaimana jika lebih dari dua substituen? Cara penamaannya hampir sama.

Untuk senyawa dengan substituen sama maka diberi nomor dengan substituen terdekat menjadi nomor 1, kemudian digunakan penamaan seperti pada senyawa organik umumnya.

Sedangkan pada substituen yang berbeda, salah satu substituen menjadi senyawa utama. Untuk lebih jelasnya, perhatikan contoh berikut ini.

Benzena dan Turunannya

Kegunaan Senyawa Benzena dan Turunannya pada Kehidupan Sehari-Hari

Tentunya kita sering sekali bertemu jenis senyawa ini, hanya saja kita sering tidak sadar dengan hal itu.

Apa saja sih kegunaan senyawa benzena ini dalam kehidupan kita? Senyawa seperti apa itu?

Berikut beberapa contoh senyawa benzena dan turunannya dalam kehidupan sehari-hari.

  • Natrium benzoat, sebagai pengawet makanan
  • Nitrobenzena, digunakan pada pewangi pada semir sepatu
  • Asam salisilat, digunakan pada obat kutil, jerawat, dan ketombe
  • Metil salisilat, digunakan pada balsam
  • Asam benzoat, merupakan bahan baku untuk membuat sakarin, dan aspirin.
  • Parasetamol, sebagai obat penurun panas
  • Vanilin, sebagai perisa dan aroma vanila

Cukup banyak bukan?

Seperti biasa untuk memahami materi lebih lanjut, ayo kita kerjakan contoh soal.

Contoh Soal Benzena dan Turunannya

1. Benzena memiliki banyak turunan. Berikut beberapa contoh struktur turunan benzena. Beri nama masing-masing senyawa ini!

Contoh Soal Benzena dan Turunannya

2. Salah satu jenis bahan peledak yaitu trinitrotoulena. Tuliskan struktur senyawa tersebut!

3. Natrium benzoat merupakan jenis pengawet turunan benzena, tuliskan struktur senyawanya!

Nah untuk ketiga soal tersebut, coba kerjakan dan cocokkan jawabannya dengan di bawah ini
Pembahasan

1. nama masing-masing senyawa:

a. Etilfenol

b. Asam metilsulfonat

c. Nitrobenzoat

d. Klorotoulena

e. Asam 3,5-dimetilsulfonat

2. Struktur trinitrotoulena seperti berikut ini.

Contoh Soal Benzena dan Turunannya 2

3. Struktur natrium benzoat seperti berikut ini.

Contoh Soal Benzena dan Turunannya 3

Penutup

Benzena merupakan senyawa dengan enam atom C yang membentuk cincin dengan satu atom H di setiap atom C dan ikatan rangkap selang-seling.

Benzena memiliki berbagai turunan yang sering kita temui. Demikian pembahasan kita kali ini, semoga bermanfaat bagi kita semua

Senin, 01 Februari 2021

MAPEL KIMIA BAB 6 REAKSI REDOKS

 

    


Di alam, reaksi kimia ada yang tergolong reaksi redoks dan bukan redoks, bagaimana cara membedakannya, di Bab ini akan dibahas  secara jelas. Contoh oksidasi misalnya perubahan warna pada irisan buah apel, pisang atau kentang yang menjadi cokelat. Proses perkaratan besi, fotosintesis, reaksi-reaksi pembakaran  juga termasuk reaksi redoks. 

A. Perkembangan Definisi

Reaksi redoks mengalami perkembangan definisi, yaitu :

    1. Berdasarkan Pengikatan dan Pelepasan Oksigen 
        Oksidasi = Reaksi pengikatan oksigen.
        Reduksi = Reaksi pelepasan oksigen.

    2. Berdasarkan Pelepasan dan Pengikatan Elektron 

        Oksidasi = Reaksi pelepasan elektron.
        Reduksi = Reaksi penangkapan elektron.

    3. Berdasarkan Kenaikan dan Penurunan Bilangan Oksidasi (Biloks)

        Oksidasi = Reaksi peningkatan biloks.
        Reduksi = Reaksi penurunan biloks.

B. Bilangan Oksidasi
 Bilangan Oksidasi menyatakan banyaknya elektron yang digunakan suatu atom untuk berikatan dengan atom lain.
Aturan Penentuan Biloks:
1. Biloks unsur atau molekul unsur = 0.
2. Biloks F dalam senyawanya selalu -1.
3. Biloks logam selalu positif.
    Golongan IA = +1 (Li, Na, K, Rb, Cs)
    Golongan IIA = +2 (Be, Mg, Ca, Sr, Ba)
    Golongan IIIA = +3 (B, Al, Ga)
    Fe  = +2, +3
    Cu  = +1, +2
    Ag  = +1
4. Biloks H dalam senyawa umumnya +1.
5. Biloks O dalam senyawa umumnya -2.
6. Biloks ion monoatomik = muatannya.


MAPEL ENGLISH LM BAB 7 Understanding General Characteristics of Poster, Pamphlet, & Banner

 

Let’s make a Banner and Pamphlet!


Understanding General Characteristics of Poster, Pamphlet, & Banner

Objectives
Responding to meaning in short formal and informal functional texts (banner, poster, pamphlet, etc.) by using variation of written text fluently and accurately in the daily life context

Learn about it!
Nowadays, there are a lot of ways to do a publication. There is a lot of media to spread information. The fastest ones are probably through phone calls, text messages, and the internet. But, how do we spread to those who do not use telecommunication devices? We use paper! Among some kinds of written publications, there are pamphlets, posters, and banner. What are the differences?

Pamphlet
The pamphlet is a kind of information which is written in a piece of paper. Some pamphlets have pictures and some of them do not have. The information on pamphlets can be printed on one side of the paper or on both sides. There is no exact size of a pamphlet. The paper can be folded into two, three or even five. The idea is to make it easy to carry and to give it to people; also people can read it anywhere. Even though it can have many pages, a pamphlet does not like a book. It comes without hardcover or binding. People use pamphlets to spread news, promote an event, or as an advertisement. Here is the example of a pamphlet:

Poster
The poster is a kind of pamphlet, but with a bigger size. It can be written in a fabric or big size paper. A poster should be big so it is easy for people to see. People place posters in strategic places. They are usually stuck on the wall. In a poster, you can see pictures and words although a poster may not contain graphics. Posters' designs are both eye-catching and informative. People use posters for many purposes. They are a tool of advertisers for particularly of events such as musicians and film, or to communicate a message. Here is the example of a poster:

Banner
A banner is a flag or other piece of cloth bearing a symbol, logo, slogan or other messages. If you happen to see a demonstration, the demonstrators usually bring banners. According to the Oxford dictionary, the banner is a long piece of cloth, often stretched between two poles, with a sign written on it, usually carried by people taking part in a march. But, now we can find the banner in many places. On the internet, the banner can be used as advertisements that appear across the top of a web page. The banner can be also in the form of written text. It is usually a slogan to raise people's awareness of the current issue. It can be also about the rule that people should obey. Here is the example of a banner:

Keypoints
Pamphlet, poster, and banner can serve the same purpose. There is no exact rule on how to use three of them. Any information can be spread through these media. However, if there is much information, you can use pamphlet. If you want it easy for people to see, use a poster or banner.

Kamis, 28 Januari 2021

MAPEL ENGLISH LM it time to sell

 

It's Time To Sell

Advertisement
Objectives
  1. Comprehending advertisement text by identifying its text structure.
  2. Writing advertisement by completing the text with appropriate language use.
Learn about it!
We almost see advertisement anywhere, and anytime. However, only a few that sticks in our head. In this lesson, you will learn how to write interesting advertisement that attracts people to buy your products. To start the lesson, let's take a look at the following picture.




The picture above is Quipper School advertisement. The tagline of Quipper School is "Learn anytime, anywhere"The tagline usually describes what or how the product is. From the advertisement above, we can see that Quipper School lets you learn anytime, any where with an internet connection. Thus, we know that Quipper School is an online learning service.
To make an interesting advertisement, there are several things to consider.

1. Structure

In writing an advertisement, the essential information is how we describe the product to the public. Before writing an advertisement for a product, you need to pay attention to:
·         The purpose of the advertisement
Think about the reason why you create the advertisement; is it to sell a product? Is it to persuade people to do something? Or else. After deciding the purpose, it will be easier to create the advertisement.
·         The target of audience
Decide who your target are: kids, teenagers, or adults; men, women or anyone else.
Create an advertisement to appeal to the target audience.
For example, you want to create an advertisement for selling candies and sweets for children. Create a tagline that will attract children such as “Share your candies and make your friendship sweeter".

2. Language Use

The advertisement should be able to persuade people, most of them will use interesting language to show the positive aspects about the products.
To appeal to the readers, an advertisement uses persuasive language. How to make it persuasive? There are several aspects that could help your advertisement sounds more persuasive:
·         Use appealing adjectives.
For example the sweetest crunchiest cookies
·         Use humor or rhetorical question.
For example how can you stop chewing?
·         Play with words (be creative with words to create a memorable slogan)
For example Best quality. Best taste. For those who always want the best.

Do you understand?

Have you noticed how to make a good advertisement? Look at the following example to enhance your understanding.


The purpose of the advertisement above is to sell a product, in this case, coffee. It promotes Besta Coffee as the best coffee. The target of the audience is people of all ages who like to drink coffee. We can see that it uses persuasive language by saying that coffee is the best in everything. It highlights the good and positive things about the product to make the product interesting.

Keypoints
To make a good advertisement, you need to:
  • decide the product or service to be presented.
  • set the target audience.
  • be creative to create your advertisement as good as possible.



Rabu, 27 Januari 2021

MAPEL ENGLISH LM BAB 7 Conjunctions: contrasting

 

Conjuction Contrasting (Although, eventhough)


Conjunctions: contrasting

Learn about it! 
The conjunctions but and although/though connect ideas that contrast. Whereas is also used but it is not as common:
The new city hall is amazing but it’s going to cost a lot.
He’s quite short, whereas his sister is tall.
But
But is a coordinating conjunction used to connect ideas that contrast. Coordinating conjunctions connect items which are the same grammatical type.
main idea
contrast
The meal was good
I want to lose weight
Lara cooked roast beef for me
Edinburgh is an interesting place
but
expensive.
I hate diets.
I don’t eat meat.
it takes a long time to get there.
Warning:
We can’t use however as a conjunction instead of but to connect words and phrases:
My teacher is very nice but a bit strict.
Not: My teacher is very nice however a bit strict.
Although/though
Although/though can be used to contrast ideas. Although/though are subordinating conjunctions used to connect a subordinate clause to a main clause, like after, as, before, if, since, that, even though, even if.
main idea
although
though
contrast
Grace is an excellent athlete
she injured her leg recently.
Harry is a great friend
we don’t see each other often.
The although/though clause can come first.
Although
Though
contrast
main idea
the car was destroyed,
no one was injured in the crash.
people say it’s dangerous,
I think it’s an amazing country.
But or although?
But cannot be used in the same way as although/though. We use but to connect items which are the same grammatical type (coordinating conjunction).
Warning:
The order of clauses connected by coordinating conjunctions cannot be reversed:
Although it rained a lot, we’ve still enjoyed our holiday.
We’ve still enjoyed our holiday, although it rained a lot.
It rained a lot but we’ve still enjoyed our holiday.
Not: But it rained a lot, we’ve still enjoyed our holiday.
Although can sound more formal than butThough is much more common in speaking than in writing. Although is much more common in writing than in speaking.
Even thougheven if
Even though and even if are also used as subordinating conjunctions in the same way as although/though. Even though is similar to although but it makes a stronger contrast:
Even though I cycle to work, I don’t feel very fit.
Even if means ‘whether or not’:
Even if you run, you’ll still be late. (You’ll be late whether you run or not.)
I feel tired even if I go to bed early. (I feel tired whether I go to bed early or not.)
Conjunctions: typical errors
·         We use and to connect words in a list and to connect phrases and clauses in a sentence:
He loves cycling, hiking and ball games.
Not: He loves cycling, hiking, ball games.
·         After conjunctions referring to time, such as when, once and as soon as, we use the present simple when we refer to the future:
It will be summer when we see you again.
Not: … when we will see you again.
They’ll leave once the lecture finishes.
Not: … once the lecture will finish.
As soon as I hear any news, I’ll call you.
Not: As soon as I’ll hear any news …
·         During is a preposition, not a conjunction, so it must be followed by a noun or a pronoun:
She studies while she is on the train.
Not: She studies during she is on the train.
·         When we use a so-clause to connect a cause/reason to a result, the so-clause must come second:
I bought a new computer game so I have no money left.
Not: So I have no money left I bought a new computer game.
·         We use although/though, not but, to connect a subordinate clause to a main clause:
Although I’m tall, I’m not as tall as Bill.
Not: But I’m tall, I’m not as tall as Bill.
·         When as well as or in addition to are followed by clauses, the verb is in the -ing form:
[from a brochure advertising an English course in London]
As well as living with a family, you practise your English.
Not: As well as you live with a family …
In addition to being a wonderful seafood restaurant, it had an amazing view.
Not: In addition to it was a wonderful seafood restaurant …
See also:
·         We cannot use however to connect words and phrases:
The area around Cannes has small but nice beaches.
Not: … has small however nice beaches.
·         We only use one conjunction to connect words or phrases:
Since she had the day off work, she went out for lunch with some friends.
Not: Since she had the day off work, so she went out for lunch …

MAPEL KIMIA BAB 11 Sistem Koloid

  Pada artikel kali ini, kita akan belajar tentang materi koloid, mulai pengertian, jenis-jenis, cara pembuatan, sampai manfaat koloid dalam...