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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PS.Chm.2.1

Molar Mass

В периодической таблице указана средняя атомная масса каждого атома. Однако макроскопические образцы содержат чрезвычайно большое количество атомов. Поэтому очень важно использовать счетную единицу, называемую числом Авогадро.Число Авогадро, обозначенное символом NA, обычно округляется до 6, 022 X 10^23. Его значение равно количеству атомов ровно в 12 граммах чистого изотопа углерода-12. Термин моль"используется для описания числа Авогадро, так же как привычный термин дюжина"используется для описания числа 12.Тем не менее, дюжина разных элементов может весить по-разному, несмотря на одинаковое количество элементов. Точно так же моли разных элементов имеют разную массу, но всегда содержат одинаковое количество атомов. Масса одного моля элемента в граммах называется молярной массой, выраженной в граммах на моль.Ее значение численно эквивалентно атомной массе элемента. Следовательно, определение моля позволяет нам подсчитывать частицы, взвешивая их. Молярная масса и число Авогадро могут использоваться как коэффициенты пересчета.Это можно использовать для расчета количества атомов в 5-граммовом слитке золота. Средняя молярная масса золота составляет 196.96 грамма на моль. Итак, чтобы преобразовать массу в моли, разделите массу слитка на среднюю молярную массу.Затем умножьте количество моль на число Авогадро, чтобы получить общее количество атомов в образце. Итак, этот золотой слиток содержит 1, 529 X 10^22 атомов.

Молярная масса

Идентичность вещества определяется не только типами атомов или ионов, которые оно содержит, но и количеством каждого типа атома или иона. Например, вода, H2O и перекись водорода, H2O2, в том, что их соответствующие молекулы состоят из атомов водорода и кислорода. Однако, поскольку молекула перекиси водорода содержит два атома кислорода, в отличие от молекулы воды, которая имеет только один, эти два вещества обладают очень разными свойствами. 
 
 Атомы и молекулы очень малы. Поэтому для измерения их макроскопических сумм необходима стандартная научная единица. Моль представляет собой единицу количества, похожую на знакомые нам единицы, такие как пара, дюжина, увеличение количества и т. д. она обеспечивает конкретную меру количества атомов или молекул в образце вещества. Латинская коннотация слова “mole” – “крупная масса” или “массовая”, что соответствует его использованию в качестве названия для этой единицы. Моль обеспечивает связь между легко измеряемым макроскопическим свойством, массой объёма и чрезвычайно важным фундаментальным свойством, количеством атомов, молекул и так далее. 
 
 Моль вещества — это количество, в котором содержится 6.02214076 × 1023 дискретных объектов (атомов или молекул). Это большое число округляется до 6.022 × 1023 и является фундаментальной константой, известной как число Авогадро (NА) или константа Авогадро в честь итальянского ученого Амедео Авогадро. Правильное прочтение этой константы - единица “на моль”. 
 
 В соответствии с определением в виде единицы количества, 1 моль любого элемента содержит такое же количество атомов, как 1 моль любого другого элемента. Массы 1 моля различных элементов, однако, отличаются, так как массы отдельных атомов существенно отличаются. Молярная масса элемента (или соединения) — масса в граммах 1 моля этого вещества, свойство, выраженное в граммах на моль (г/моль). 
 
 Молярная масса любого вещества численно эквивалентна его атомному весу в amu. Согласно определению amu, один атом углерода весит 12 amu (его атомная масса равна 12 аму). Моль углерода весит 12 г (12 г C = 1 моль C атомов = 6.022 × 1023 C атомов), а молярная масса углерода составляет 12 г/моль. Это отношение относится ко всем элементам, поскольку их атомные массы измеряются относительно массы amu эталонного вещества, углерода, которая равна 12. Расширяя этот принцип, молярная масса вещества в граммах также численно эквивалентна его атомной массе в amu. Например, гелий имеет атомную массу 4.002 amu и молярную массу 4.002 г/моль. 
 
 В то время как атомная масса и молярная масса являются численно эквивалентными, имейте в виду, что они значительно отличаются по масштабам. Чтобы оценить, насколько велик моль, рассмотрим небольшую каплю воды весом около 0.03 г. Несмотря на то, что это составляет всего лишь малую часть 1 моля воды (~18 г), она содержит больше молекул воды, чем можно себе представить. Если бы молекулы распределялись равномерно среди примерно семи миллиардов человек на земле, каждый человек получил бы более 100 миллиардов молекул воды. 
 
 Моль определяет связь между массой и количеством атомов. Это позволяет рассчитать количество атомов на основе подходящих форм коэффициента преобразования: 1 моль атомов = 6.022 × 1023 атомов. Для преобразования массы элемента (в граммах) и чилом молей в качестве коэффициента преобразования используется молярная масса элемента (г/моль). 
 
 Текст, адаптированный из <a href=""https://openstax.org/books/chemistry-2e/pages/3-1-formula-mass-and-the-mole-concept"">Openstax Химия 2e, раздел 3.1: Концепция атомной массы и моля.</a>"

Идентичность вещества определяется не только типами атомов или ионов, которые оно содержит, но и количеством каждого типа атомов или ионов. Например...

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ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

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 ×...

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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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Mole, Mass, and Avogadro’s Number

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