化学の計算で必ず出てくる「mol（モル）」って、実は超シンプルな考え方なんだ。原子や分子を1個ずつ数えるのは無理だから、決まった個数をまとめて「1セット」として扱うだけ。これを理解すれば化学の計算問題がグッと楽になるよ。
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Updated Mar 16, 2026
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アボガドロ定数とモルの基本: 簡単な計算方法
1 / 5
物質量とアボガドロ定数の基本
**物質量（mol）**は、原子や分子の「個数の集団」を表す単位だ。鉛筆12本を「1ダース」と呼ぶのと同じ感覚で、1 mol = 6.02 × 10²³個の粒子の集まりを意味する。
アボガドロ定数（NA = 6.02 × 10²³ /mol）は絶対に覚えよう。これは1 molあたりの粒子数を表している。
原子量・分子量・式量はすべて単位がない相対的な数値。でもモル質量は「g/mol」という単位がついて、数値は原子量などと同じになる。例えば水（H₂O）の分子量は18だから、モル質量は18 g/molだ。
💡 重要ポイント：「mol」を中心に考えると、すべての変換がスムーズにできる！
質量・物質量・粒子数の三角関係
化学計算で一番大切なのは、**質量（g）、物質量（mol）、粒子の数（個）**の相互変換だ。すべての計算の中心に「mol」があると覚えておこう。
質量からmol：質量 ÷ モル質量 = mol molから質量：mol × モル質量 = 質量 molから粒子数：mol × アボガドロ定数 = 粒子数 粒子数からmol：粒子数 ÷ アボガドロ定数 = mol
まず「mol」を求めてから他の量に変換する、という流れで考えると分かりやすい。どの公式を使うか迷ったら、単位を見ながら計算すると間違えにくいよ。
💡 計算のコツ：単位も一緒に書きながら計算すると、どの操作をすべきか一目瞭然！
実践的な計算例
例題1：CO₂ 22gの物質量と分子数を求めてみよう。
まずCO₂の分子量を計算：C（12）+ O（16）× 2 = 44 だからモル質量は44 g/mol
物質量 = 22g ÷ 44 g/mol = 0.50 mol 分子数 = 0.50 mol × 6.0×10²³ /mol = 3.0×10²³個
例題2：1.2×10²⁴個の水分子の物質量と質量は？
物質量 = 1.2×10²⁴個 ÷ 6.0×10²³ /mol = 2.0 mol H₂Oの分子量は18だから、質量 = 2.0 mol × 18 g/mol = 36g
💡 計算の順序：必ず「mol」を経由して他の量に変換する習慣をつけよう！
テスト対策と重要ポイント
単位の使い分けに注意しよう。原子量・分子量・式量は無単位、モル質量には「g/mol」がつく。計算途中でも単位を書くクセをつけると、ミスが激減する。
分子数 vs 原子数の区別も超重要。メタン（CH₄）1molには分子が6.02×10²³個あるけど、原子は炭素1mol+水素4mol=合計5molの原子が含まれている。
有効数字は与えられた数値の中で最も桁数が少ないものに合わせるのが基本。22g（2桁）の計算結果なら、答えも2桁で表そう。
テストでよく出るのは、これらの変換を組み合わせた問題。焦らず「まずmolを求める」という基本に立ち返れば大丈夫だ。
💡 暗記必須：mol = g/ と 個数 = mol × NA の2つの式だけ覚えれば完璧！
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I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
アボガドロ定数とモルの基本: 簡単な計算方法
化学の計算で必ず出てくる「mol（モル）」って、実は超シンプルな考え方なんだ。原子や分子を1個ずつ数えるのは無理だから、決まった個数をまとめて「1セット」として扱うだけ。これを理解すれば化学の計算問題がグッと楽になるよ。
物質量とアボガドロ定数の基本
**物質量（mol）**は、原子や分子の「個数の集団」を表す単位だ。鉛筆12本を「1ダース」と呼ぶのと同じ感覚で、1 mol = 6.02 × 10²³個の粒子の集まりを意味する。
アボガドロ定数（NA = 6.02 × 10²³ /mol）は絶対に覚えよう。これは1 molあたりの粒子数を表している。
原子量・分子量・式量はすべて単位がない相対的な数値。でもモル質量は「g/mol」という単位がついて、数値は原子量などと同じになる。例えば水（H₂O）の分子量は18だから、モル質量は18 g/molだ。
💡 重要ポイント：「mol」を中心に考えると、すべての変換がスムーズにできる！
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質量・物質量・粒子数の三角関係
化学計算で一番大切なのは、**質量（g）、物質量（mol）、粒子の数（個）**の相互変換だ。すべての計算の中心に「mol」があると覚えておこう。
質量からmol：質量 ÷ モル質量 = mol molから質量：mol × モル質量 = 質量 molから粒子数：mol × アボガドロ定数 = 粒子数 粒子数からmol：粒子数 ÷ アボガドロ定数 = mol
まず「mol」を求めてから他の量に変換する、という流れで考えると分かりやすい。どの公式を使うか迷ったら、単位を見ながら計算すると間違えにくいよ。
💡 計算のコツ：単位も一緒に書きながら計算すると、どの操作をすべきか一目瞭然！
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実践的な計算例
例題1：CO₂ 22gの物質量と分子数を求めてみよう。
まずCO₂の分子量を計算：C（12）+ O（16）× 2 = 44 だからモル質量は44 g/mol
物質量 = 22g ÷ 44 g/mol = 0.50 mol 分子数 = 0.50 mol × 6.0×10²³ /mol = 3.0×10²³個
例題2：1.2×10²⁴個の水分子の物質量と質量は？
物質量 = 1.2×10²⁴個 ÷ 6.0×10²³ /mol = 2.0 mol H₂Oの分子量は18だから、質量 = 2.0 mol × 18 g/mol = 36g
💡 計算の順序：必ず「mol」を経由して他の量に変換する習慣をつけよう！
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テスト対策と重要ポイント
単位の使い分けに注意しよう。原子量・分子量・式量は無単位、モル質量には「g/mol」がつく。計算途中でも単位を書くクセをつけると、ミスが激減する。
分子数 vs 原子数の区別も超重要。メタン（CH₄）1molには分子が6.02×10²³個あるけど、原子は炭素1mol+水素4mol=合計5molの原子が含まれている。
有効数字は与えられた数値の中で最も桁数が少ないものに合わせるのが基本。22g（2桁）の計算結果なら、答えも2桁で表そう。
テストでよく出るのは、これらの変換を組み合わせた問題。焦らず「まずmolを求める」という基本に立ち返れば大丈夫だ。
💡 暗記必須：mol = g/ と 個数 = mol × NA の2つの式だけ覚えれば完璧！
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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4.7/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user