Name: mole, mass, and avogadro’s number
Uploaded: 2020-09-03T13:38:25.000Z
Duration: 1 min 54 s
Channel: JoVE

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NC K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.2.1

Molar Mass

يعطي الجدول الدوري متوسط الكتلة الذرية لكل ذرة. ومع ذلك،تحتوي العينات العيانية على أعداد كبيرة للغاية من الذرات. لذلك،من الضروري استخدام وحدة حساب تسمى رقم أفوجادرو.رقم أفوجادرو،معبرًا عنه بالرمز NA،يتم تقريبه عادةًإلى 6.022 10 23. قيمتها تساوي عدد الذرات في 12 جرامًا بالضبط من نظير الكربون 12 النقي. مصطلح Mole"واختصاره Mol"يستخدم لوصف رقم أفوجادرو،تمامًا مثل المصطلح المألوف،دزينة،الذي يستخدم لوصف الكمية 12.ومع ذلك،هناك دزينة من العناصر المختلفة يمكن أن تزن بشكل مختلف على الرغم من وجود نفس عدد العناصر. بشكل مماثل،مولات العناصر المختلفة لها كتل مختلفة لكنها تحتوي دائمًا على نفس عدد الذرات. الكتلة بالجرام لمول واحد من عنصر تسمى الكتلة المولية،معبرًا عنها بالجرام لكل مول.قيمته مكافئة عدديًا للكتلة الذرية للعنصر. لذلك،تعريف المول يتيح لنا عد الجسيمات من خلال وزنها. الكتلة المولية وعدد أفوجادرو يمكن استخدامهما كعوامل تحويل.يمكن استخدام هذا لحساب عدد الذرات في سبيكة من الذهب بوزن 5 جرام. متوسط الكتلة المولية للذهب 196.96 جرام لكل مول. لذلك،لتحويل الكتلة إلى مولات،نقسم كتلة السبيكة على متوسط الكتلة المولية،ثم نضرب عدد المولات في رقم أفوجادرو للحصول على إجمالي عدد الذرات في العينة.لذلك،يحتوي هذا الشريط من الذهب على 1.529 10 22 ذرة.

الكتلة المولية

يتم تحديد هوية المادة ليس فقط من خلال أنواع الذرات أو الأيونات التي تحتويها ولكن أيضًا من خلال كمية كل نوع من الذرات أو الأيونات. على سبيل المثال، الماء، H 2 O، وبيروكسيد الهيدروجين، H 2 O 2 ، متشابهان من حيث أن جزيئات كل منهما تتكون من ذرات الهيدروجين والأكسجين. ومع ذلك، نظراً لأن جزيء بيروكسيد الهيدروجين يحتوي على ذرتين من الأكسجين، على عكس جزيء الماء، الذي يحتوي على جزيء واحد فقط، فإن المادتين لهما خصائص مختلفة جدًا. الذرات والجزيئات صغيرة للغاية. لذلك، لقياس كمياتها الظاهرة للعين المجردة، هناك حاجة إلى وحدة علمية قياسية. الخلد هو وحدة مقدار مماثلة للوحدات المألوفة مثل زوج، دزينة، إجمالي، إلخ. ويوفر مقياسًا محددًا لعدد الذرات أو الجزيئات في عينة من المادة. الدلالة اللاتينية لكلمة “مول” هي “كتلة كبيرة” أو “كتلة ضخمة,” وهذا ما يتوافق مع استخدامها كاسم لهذه الوحدة. يوفر المول رابطًا بين الخاصية الظاهرة للعين المجردة، الكتلة الكبيرة، والتي يتم قياسها بسهولة، وبين الخصائص الأساسية البالغة الأهمية، كعدد الذرات، والجزيئات، وما إلى ذلك. المول في المادة هو المقدار الذي يوجد فيه 6.02214076 × ؛ 10 23 من الكيانات المنفصلة (ذرات أو جزيئات). يتم تقريب هذا الرقم الكبير بشكل ملائم إلى 6.022 مرات ؛ & nbsp ؛ 10 23 ، وهو ثابت أساسي يُعرف باسم رقم أفوكادرو’s (N A ) أو ثابت أفوكادرو تكريمًا للإيطالية العالِمة أميديو أفوجادرو. يتم التعبير عن هذا الثابت بشكل صحيح بوحدة صريحة من “بالمول”. تماشيا مع تعريفها كوحدة كمية، يحتوي 1 مول من أي عنصر على نفس عدد الذرات في 1 مول من أي عنصر آخر. ومع ذلك، فإن كتلة 1 مول من عناصر مختلفة هي ليست متساوية، لأن كتل الذرات الفردية تختلف اختلافًا جذريًا. الكتلة المولية لعنصر (أو مركب) هي الكتلة بالغرام من 1 مول من تلك المادة، وهي خاصية معبر عنها بوحدات الغرام لكل مول (غ/مول). الكتلة المولية لأي مادة تعادل عددياً وزنها الذري أو وزنها في amu. وفقًا لتعريف amu ، تزن ذرة كربون واحدة 12 amu (كتلتها الذرية هي 12 amu). يزن مول من الكربون 12 غم (12 غم C = 1 جزيء غرامي من ذرات الكربون = 6.022 مرة ؛ 10 23 C ذرات)، والكتلة المولية للكربون هي 12 غم/مول. تنطبق هذه العلاقة على جميع العناصر حيث يتم قياس كتلها الذرية بالنسبة إلى تلك الموجودة في المادة المرجعية amu ، الكربون -12. لتوسيع هذا المبدأ ، فإن الكتلة المولية للمركب بالغرام تعادل عدديًا وزنها في amu. على سبيل المثال، للهيليوم كتلة ذرية قدرها 4.002 amu والكتلة المولية 4.002 غم/مول. بينما الكتلة الذرية والكتلة المولية متساويتان عددياً ، ضع في اعتبارك أنهما يختلفان اختلافاً كبيراً من حيث الحجم. لتقدير ضخامة المول، ضع في اعتبارك أن قطرة ماء صغيرة تزن حوالي 0.03 غرام. على الرغم من أن هذا يمثل جزءًا صغيرًا من مول واحد من الماء (حوالي 18 غم) ، إلا أنها تحتوي على جزيئات ماء أكثر مما يمكن تخيله. إذا تم توزيع الجزيئات بالتساوي بين ما يقرب على سبعة مليارات شخص على وجه الأرض، فسيحصل كل شخص على أكثر من 100 مليار جزيء من الماء. يحدد المول العلاقة بين الكتلة وعدد الذرات. يسمح هذا بحساب عدد الذرات على أساس استخدام المعادلات المناسبة لعامل التحويل: 1 مول من الذرات = 6.022 & مرات ؛ 10 ذرات 23 . للتحويل بين كتلة عنصر (بالغرام) وعدد المولات، يتم استخدام الكتلة المولية للعنصر (غم/مول) كعامل تحويل. النص مقتبس من <a href="https://openstax.org/books/chemistry-2e/pages/3-1-formula-mass-and-the-mole-concept">Openstax Chemistry 2e, Section 3.1: Formula Mass and the Mole Concept.</a>

لا يتم تحديد هوية المادة من خلال أنواع الذرات أو الأيونات التي تحتوي عليها فحسب ، بل من خلال كمية كل نوع من أنواع الذرة أو الأيونات. على سبيل المثال...

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Atoms and Elements

الذرات والعناصر

KEY TERMS AND CONCEPTS

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mole, mass, and avogadro’s number

The mole links mass and the number of particles in a substance. It gives chemists a standard way to count atoms and molecules in samples that are far too small to see. It also helps show why substances with the same kinds of atoms can still have very different properties, like water, H2O, and hydrogen peroxide, H2O2.

The mole is an amount unit, like a pair or a dozen. One mole contains 6.02214076 × 10^23 discrete entities, such as atoms or molecules. This number is usually rounded to 6.022 × 10^23 and is called Avogadro’s number, or the Avogadro constant, named for Amedeo Avogadro. The constant is written with the unit per mole.

One mole of any element contains the same number of atoms as one mole of any other element. The masses are different, though, because atoms have different individual masses. That is why one mole of one element does not weigh the same as one mole of another element.

Molar mass is the mass in grams of one mole of a substance. It is reported in grams per mole, or g/mol. The molar mass of an element or compound is numerically equal to its atomic mass or formula mass in amu. For example, carbon has an atomic mass of 12 amu, so 1 mole of carbon has a mass of 12 g and a molar mass of 12 g/mol.

This same relationship works for other elements and for compounds. Helium, for example, has an atomic mass of 4.002 amu and a molar mass of 4.002 g/mol. Although the numbers match, atomic mass and molar mass are very different in scale.

A tiny drop of water can still contain an enormous number of molecules. A drop that weighs about 0.03 g is only a small part of 1 mole of water, which is about 18 g. Even so, it holds more water molecules than can easily be imagined. If those molecules were shared equally among the roughly seven billion people on Earth, each person would still get more than 100 billion molecules of water.

The mole also lets scientists convert between mass and amount. Using the relationship 1 mole of atoms = 6.022 × 10^23 atoms, the number of atoms can be calculated from a sample. The molar mass of an element is also used as a conversion factor to move between grams and moles.

Mole, Mass, and Avogadro’s Number

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molar mass

The mole links mass and the number of particles in a substance. It gives chemists a standard way to count atoms and molecules in samples that are far too small to see. It also helps show why substances with the same kinds of atoms can still have very different properties, like water, H2O, and hydrogen peroxide, H2O2. The mole is an amount unit, like a pair or a dozen. One mole contains 6.02214076 × 10^23 discrete entities, such as atoms or molecules. This number is usually rounded to 6.022 ×...

key terms and concepts

Learn how the mole connects mass, atoms, and molecules through Avogadro’s number and molar mass, with clear examples for high school chemistry.

Mole, Mass, and Avogadro’s Number | JoVE K12

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Structure And Properties Of Matter

Quantifying matter

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Mole, Mass, and Avogadro’s Number

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