MAPEL KIMIA Stoikiometri Larutan

 Daftar Isi  

Pengertian Rumus Molekul dan Rumus Empiris

Menentukan Rumus Empiris

Contoh soal 1

Menentukan Rumus Molekul

Contoh soal 2

Melengkapi Persamaan Reaksi Kimia

Pengertian Stoikiometri

Pengertian Pereaksi Pembatas

Penentuan Pereaksi Pembatas

Senyawa Hidrat (Air Kristal)

Contoh soal 3

Contoh soal 4

Pengertian Rumus Molekul dan Rumus Empiris

Seperti pada pembahasan di awal, pupuk merupakan senyawa penting yang berperan dalam menyuburkan tanaman. Pupuk yang biasa digunakan adalah urea. Pupuk urea memiliki rumus molekul CH₄N₂O. Rumus molekul adalah rumus yang menunjukkan jumlah atom setiap unsur dalam suatu senyawa. Ternyata, rumus molekul inilah yang biasa digunakan untuk lambang suatu senyawa. Membahas rumus molekul tentu tidak bisa lepas dari rumus empiris. Apa itu rumus empiris? Rumus empiris adalah rumus yang memiliki perbandingan atom-atom paling sederhana dalam suatu senyawa.

Menentukan Rumus Empiris

Untuk menentukan rumus empiris, ada beberapa langkah yang harus Quipperian lakukan, yaitu sebagai berikut.

1. Rumus empiris bisa ditentukan melalui rumus molekul, yaitu dengan menyederhanakan jumlah atom penyusun rumus molekul agar diperoleh bilangan bulat paling kecil.
2. Rumus empiris juga bisa ditentukan melalui perbandingan mol unsur-unsur penyusun senyawa, dengan syarat massanya diketahui.

Untuk meningkatkan pemahaman Quipperian, simak contoh soal berikut.

Contoh soal 1

Tentukan rumus empiris senyawa C₆H₁₂O₆!

Pembahasan:

Rumus empiris diperoleh dengan menyederhanakan rumus molekul, seperti berikut ini.

C₆H₁₂O₆ = (CH₂O)₆

Dengan demikian, rumus empiris dari C₆H₁₂O₆ adalah CH₂O.

Menentukan Rumus Molekul

Rumus molekul merupakan rumus yang jumlah atomnya kelipatan dari rumus empiris. Namun demikian, ada beberapa senyawa yang memiliki rumus molekul dan empiris sama. Untuk menentukan rumus molekul, gunakan persamaan berikut.

Keterangan:

n merupakan kelipatan rumus empiris terhadap rumus molekul.

Untuk meningkatkan pemahaman Quipperian tentang rumus molekul, perhatikan contoh soal berikut.

Contoh soal 2

Suatu senyawa memiliki rumus empiris CH₂O. Jika Mr senyawa tersebut 150, tentukan rumus molekul senyawa tersebut! (Ar H = 1, C = 12, dan O = 16)

Pembahasan:

Sebelum mencari rumus molekul senyawa tersebut, tentukan dahulu massa molekul relatifnya (Mr)!

Selanjutnya, Quipperian harus menentukan nilai n menggunakan persamaan berikut.

Jika nilai n sudah diketahui, Quipperian bisa mencari rumus molekulnya seperti cara berikut.

Jadi, rumus molekul senyawa tersebut adalah C₅H₁₀O₅.

Melengkapi Persamaan Reaksi Kimia

Reaksi kimia merupakan reaksi yang berlangsung secara spontan. Jika suatu senyawa yang mengandung ion negatif direaksikan dengan senyawa lain yang mengandung ion positif, maka ion-ion tersebut bisa saling berikatan. Ikatan antarion tersebut bisa Quipperian lihat pada contoh berikut.

Pengertian Stoikiometri

Stoikiometri adalah ilmu kimia yang mempelajari tentang kuantitas suatu zat, meliputi massa, jumlah mol, volume, dan jumlah partikel. Saat mempelajari stoikiometri, Quipperian akan selalu bertemu dengan koefisien. Apa itu koefisien? Koefisien merupakan bentuk perbandingan mol, volume, atau jumlah partikel. Adapun rumus-rumus yang biasa digunakan dalam menyelesaikan stoikiometri adalah sebagai berikut.

Pengertian Pereaksi Pembatas

Membahas reaksi kimia, sama artinya membahas zat pereaksi dan produk hasil reaksi. Zat pereaksi biasanya ditulis di ruas kiri, sedangkan produk ditulis di ruas kanan. Zat pereaksi tersebut akan berubah menjadi produk jika memenuhi perbandingan koefisien tertentu. perbandingan koefisien biasanya mengacu pada jumlah mol yang terlibat selama reaksi berlangsung. Penentuan mol produk didasarkan pada perbandingan koefisien mol zat pereaksi. Nah, jika mol pereaksinya berasal dari dua zat yang bereaksi, maka perlu dicari acuan yang tepat. Acuan itu disebut sebagai pereaksi pembatas. Mol zat yang digunakan sebagai pereaksi pembatas ini akan habis bereaksi.

Penentuan Pereaksi Pembatas

Untuk menentukan pereaksi pembatas, Quipperian bisa menggunakan persamaan berikut.

Senyawa Hidrat (Air Kristal)

Kristal adalah zat padat homogen yang dibatasi oleh bidang-bidang datar dan memiliki bentuk tertentu. ada beberapa senyawa yang bisa ditemukan dalam bentuk kristal, contohnya garam Inggris (MgSO₄.7H₂O). Kristal dalam senyawa tersebut merupakan hasil perubahan wujud air menjadi padatan.

Tampaknya, belajar Kimia tidak akan sah jika belum latihan soal ya Quipperian. Oleh karena itu, Quipper Blog telah merangkum beberapa contoh soal untuk Quipperian. Check this out!

Contoh soal 3

Perhatikan persamaan reaksi kimia berikut ini.

 

Jika gas SO₂ yang direaksikan sebanyak 12,8 gram, tentukan volume gas O₂ diukur pada keadaan standar (STP) dan massa SO₃ yang terbentuk!

Pembahasan:

1. Untuk menentukan volume gas O₂, Quipperian harus mencari massa molekul relatif gas O₂ dan SO₂ tersebut.

Kemudian, tentukan mol gas SO₂ dan O₂.

 

Volume O₂ pada keadaan STP dirumuskan sebagai berikut.

 

2. Untuk mencari massa SO₃ yang terbentuk, Quipperian juga harus mencari massa molekul relatif dan mol gas SO₃.

Massa gas SO₃ yang terbentuk dirumuskan sebagai berikut.

Jadi, volume gas O₂ diukur pada keadaan standar (STP) dan massa SO₃ yang terbentuk berturut-turut adalah 2,24 L dan 16 gram.

Bagaimana Quipperian, mudah bukan? Ayo lanjut ke contoh soal berikutnya.

Contoh soal 4

Sebanyak 22 gram C₃H₈ direaksikan dengan 48 gram O₂ berdasarkan persamaan reaksi berikut.

Tentukan zat yang merupakan pereaksi pembatas dan massa zat yang tersisa!

Pembahasan:

1. Untuk menentukan zat pereaksi pembatasnya, Quipperian harus mencari massa molekul relatif dan mol C₃H₈ dan O₂.

Setelah massa molekul relatif dan mol dari C₃H₈ dan O₂ sudah diketahui, Quipperian harus menyetarakan persamaan reaksinya seperti berikut ini.

Pereaksi pembatasnya bisa ditentukan dengan persamaan berikut.

Zat yang berperan sebagai pereaksi pembatas adalah zat yang hasil baginya palingg kecil. Oleh karena hasil bagi O₂ lebih kecil daripada C₃H₈, maka zat yang berperan sebagai pereaksi pembatas adalah O₂.

2. Pada reaksi di atas, zat yang tersisa adalah C₃H₈, sehingga Quipperian harus mencari massa C₃H₈ yang tersisa. Sebelum mencari massa C₃H₈ yang tersisa, Quipperian harus tahu berapa jumlah mol C₃H₈ yang tersisa.

 

Jadi, zat yang merupakan pereaksi pembatas dan massa zat yang tersisa berturut-turut adalah O₂ dan 8,8 gram C₃H₈.

MAPEL ENGLISH LM Report Text

 

REPORT TEXT: NATURAL PHENOMENA

Report Text: Natural Phenomena

How many times do you see sunset?
How many times do you get wet because of being caught in the rain?
How many times do you capture rainbow on the sky?
You may see and experience those beautiful natural phenomena for many times, perhaps. But, have you ever questioned yourself how sunset, rainbow, rain, or other phenomena occur? By discovering the answer of such questions, we will come in amazement. How wonderful our world and this nature is!

Learn about it!

Try it!

Rainbow
Rainbow is an optical phenomena. It is made of droplets of water when sunlight appears in the angle of sky opposing the sun. When the light enters water droplets, the different spectrum of colors bend at separate angles. That is the reflection, refraction and dispersion of light in water droplets which create the spectrum of light. Besides rain, rainbow can also be caused by many forms of airborne water, such as spray, mist, and airborne dew. A rainbow is not an object. We cannot physically approach it. However, we can see it when we stay in the right angle.

Well, after reading the text, we know the process of how the rainbow, one of natural phenomena, happens. It is the result of light reflection, refraction, and dispersion in water droplets. The text above is an example of a report text; a text where we can find explanations of many things, including natural phenomena.

So, what is a report text?

Report text is a text presenting information of something, supported by facts resulted from analysis and observation. The purpose of the text is to inform the reader about something.

What is the generic structure of the text?

A report text consists of general information and bundles of specific information. General information is a part that delivers the general description of the theme. Meanwhile, bundles of specific information consist of specific descriptions of the theme. Here is the example of a report text identification.

Then, what are the characteristics of a report text?

• describing general things
• using present tense
• using general nouns such as the dolphin instead of her dolphin

Keypoints

So, when you read a report text, you will get more knowledge about many things including natural phenomena. Besides that, when you are about to write an explanation of something, you should consider the structure of report text.

From this section you have learnt about a report text. There are some points you need to remember.

• Purpose of a report text : to inform the reader about something
• Generic structure of a report text general information: a part which delivers the general description of the theme bundles of specific information: specific descriptions of the theme.
• Characteristics of a report text Describing general things Using present tense Using general nouns

Developing Paragraph of Report Texts

Objectives of Study

Understanding monolog text report of spoken and written in order to access the knowledge in daily life context. After this study, Students are expected

·         Able to construct a topic sentence, supporting sentence, and developing sentence in form of spoken and written text.

·         Able to develop a paragraph writing.

Learn about It

Lets come back on study English. In this occasion, I would like to discuss about paragraph writing. Before we study it, lets we listen the meteorologist are talking about clouds.

After listen the meteorologist explains about clouds, we can focus on how the speaker contracted his explanation by developing his topic sentence. The meteorologist said “ Clouds have two effects”

Clouds have two effects is the topic sentence. Topic sentence is consist of Subject and Controlling Idea.Look at he chart below!

So, the outline of paragraph writing is

Paragraph Writing

·         Supporting sentence

o   Developing sentence

§  Provide examples

§  Back up

§  Illustrate

§  Explain

§  Clarify

·         Supporting sentence

o   Developing sentence

§  Provide examples

§  Back up

§  Illustrate

§  Explain

§  Clarify

We can state that Paragraph is group of related sentences that develop an idea. It is consisted of topic sentence, supporting sentence, and developing sentence. To make a good paragraph, try to make the clear topic and provide a details. Listen another meteorologist are talking about weather condition, it is monsoon.

Most islands have winds that change direction once a year. These winds are called monsoons. The winds carry moist air part of the year and dry air the other part. On high islands, monsoons create a wet and a dry season. This is because the mountains trap the moist air, causing rain. Low islands are usually dry because there are no mountains to catch the air.Tropical storms hit the islands yearly. Sometimes the storms bring heavy wind and rains. The storms can cause severe damage.

We will study some vocabularies which related with weather conditions such as:

Monsoon= heavy rain with strong wind in summer in the South Asia (Portuguese word)

Another words which related with weather conditions are:

Cyclone = a violent strong wind which move in circle (Greek word)

Typhoon= a violent tropical storm with strong wind (Chinese word)

Thunderstorm= storm with thunder and lightning with heavy rain

Tsunami= destructive waves cause by earthquake in the sea (Japanese Word)

Tornado=  a violent strong wind which move in circle (Spanish word)

English is always changing because it always absort  new words from other languages such as the word cyclone originally came from Greek word, Word Typhoon came from Chinese, word monsoon came from Portuguese word, word Tsunami came from Japanese word and word Tornado came from Spanish word. Not only the words which stating above but also there are tremendous English words which originally came from other languages.

To make your English sound naturally, you should practice your English a lot in terms of Pronunciation, Intonation and sentence rhythm and add your vocabularies!

Do You Understand?

Lets practice in making short paragraph writing. Topic: English word, Controlling Idea: come from other languages.

Key Points

1.      Paragraph is a group of related sentences that develop an idea.

2.      It is consisted by topic sentence, supporting sentence, and developing sentence.

3.      Many English words come from other languages such as: ‘Monsoon’, ‘tornado’, and ‘tsunami’ are words from Portuguese, Spanish, and Japanese.

MAPEL ENGLISH LM Exploring Movie Reviews

 

Exploring Movie Reviews

Exploring Movie Reviews

Objectives

Understanding the meaning (function), form, and use of the adjective based on its context.

Learn about it!

In this lesson, you will learn about how to understand the Definition, Generic structure, social function, meaning, form, and use of adjectives, especially for a movie review.

1. What is a review text?

1.    Definition

The review is one of the text genres. This classification of text types is commonly based on the structure used by the writer to compose his text. Each text type will have a different form of generic structure. As I said in my previous post, review text usually has a generic structure as:

2.    Generic Structure

Introduction: it is the highlight of the general description of what will be reviewed. It can be the product, services that want to be sold, or just a site which wants to be known publicly. Then it will drive more traffic into the site.

Evaluation: the second phase is coming inside into the product in detail. It states the parts, uniqueness, quality of the product which will be known publicly. However, too much detail description will “teach” the will-buyer and it does not sound good. Evaluating as far as necessary for the targeted buyer is more genuine. The term evaluation will not be far from simple words of good or bad. In this phase reviewer will apply much evaluative word, valuable, useful, worthy, etc.

Interpretation: after writing about the objective thing of the product, it is the time for the reviewer to write about what he thinks or impresses on the product. Of course, this phase can be done after getting enough evaluation of the product. It is a personal idea about the product. Frequently to support and strengthen his idea or impression, a reviewer describes a comparison to other similar products. He states in which side the product has added value or honestly admitted that the product lacks value in a certain side.

Summary: this phase is recommending the conclusion for the reader of the product. After a clear explanation, a reviewer will make a final comment on whether the product is valuable or not for the targeted buyer. This phase is the worth of the review for the reader.

3.    Dominant Language features:

1. Focus on specific participants

2. Using adjectives

3. Using long and complex clauses

4. Using metaphor

4.    Examples and structures of the text

Harry Potter: Order of the Phoenix
Pengenalan / Orientasi	I absolutely love the Harry Potter series, and all of the books will always hold a special place in my heart.
Evaluasi 1	I have to say that of all of the books, however, this was not my favorite.
Evaluasi 2	When the series began it was as much of a "feel good" experience as a huge mug of hot cocoa. The stories were bright, fast-paced, intriguing, and ultimately satisfying.
Tafsiran (Interpretative recount)	Order of the Phoenix is a different kind of book. In some instances this works...you feel a whole new level of intensity and excitement by the time you get to the end. I was truly moved by the last page. Other times the book just has a slightly dreary, depressing feel. The galloping pace of the other books has slowed to a trot here, and parts of it do seem long, as if we're reading all about Harry "just hanging out" instead of having his usual adventures. Reading in detail about Harry cleaning up an old house, for example - housekeeping is still housekeeping, magical or no, and I'm not very interested in doing it or reading about other people doing it.  A few other changes in this book - the "real" world comes much more in to play rather than the fantasy universe of the previous books, and Harry has apparently been taken off his meds. I know that he had a lot to be grumpy in this book, especially with being a teenager and all, but the sudden change in his character seemed too drastic. He goes from being a warm-hearted, considerate person to someone who will bite his best friend's heads off over nothing. It just seemed like it didn't fit with his character, like he turned into a walking cliché of the "angry teen" overnight.
Rangkuman	The "real" story seemed to happen in the last 1/3 of the book, and this part I loved. I actually liked the ending (and yes, I cried!) as sad as it was. It packed a punch and it made me care about the story even more. Still a really good book, with some editing it would have been great.

2. The function of adjectives in movie review

Have you ever written a movie review? Do you know what you should put into a movie review? In writing a movie review, you do not only need to pay attention to its generic structures, but also its language features such as using persuasive language, present tense, adjective, and complex sentences. However, in this lesson, you will only focus on how to use an adjective in writing a movie review. Using proper adjectives in a movie review is important to make a judgment. The adjectives describe the movie whether it is recommended or not.

3. The forms of Adjectives

An adjective is a word that modifies the noun or a pronoun. It is put after the linking verb (auxiliary). For example:

The movie is amazing.

• Noun: The movie
• Auxiliary: is
• Adjectives: amazing

I am amazed.

• Pronoun: I (the movie)
• Auxiliary: am
• Adjectives: amazed

The examples above show that the adjective “amazing” and "amazed" modify the noun and pronoun “the movie" and "I". The adjective is put after auxiliary “is” and"am". See another example below:

1. Her character as a writer was interesting.
2. I am interested in her character as a writer in that movie.

Have you identified the difference between the first and the second sentences above? Well, the sentences above have two meaning; an active meaning and a passive meaning. The word “interesting” and “interested” are from “interest”, but when you put participle –ing and –ed to make an adjective, the meaning changes.

• Her character as a writer was interesting. (It means that the character as a writer interests you)

When you put participle –ing, the adjective has an active meaning.

• I am interested in her character as a writer in that movie. (It means that you have an interest or feel interested in the character.)

But, when you put participle –ed, the adjective has a passive meaning.

Look at the table below to see another adjective with participle -ing and -ed.

To make an adjective has a stronger meaning you can use words such as very, really, absolutely, and extremely.
Those words are called as ***intensifier*. For examples:

• It must be a really great movie
• They were extremely excited in watching that movie
• I think this movie won’t disappoint you. It is absolutely touching, witty, deep, and refreshing.

4. The use of adjectives

Adjectives are commonly placed after to be (am, are, is, was, were). However, there are some other verbs that can be followed by adjectives.

To understand how to use the words above, read the following sentences:

The director is genius in making the high quality 3D movie.
The director seems genius in making the high quality 3D movie.

She is very amazed at the story in the movie.
She feels very amazed with the story in the movie.

They feel so sleepy while watching because the movie is boring.
They feel so sleepy while watching because the movie feels boring.

After reading the explanation about form and meaning of the adjective. Now, try to understand how to use the adjective in a movie review both orally and written. Here are the examples of using adjectives in a movie review.

Do you understand?

Example of conversation:
Keyla : Have you watched ‘Letters to Juliet’ movie?
Rizal : No. What kind of movie is it?
Keyla : It is an amazing drama movie.
Rizal : What is it about?
Keyla : It tells about an old lady looks for her past boyfriend then they meet after 50 years because of letter to Juliet.

Example of text:
‘Letters to Juliet’ is an amazing movie. I absolutely loved it. It is extremely amusing because providing a lot of beautiful places in Verona, Italy. The story is also romantic and touching. You won’t regret it.'