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

K12 Standards

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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

Das Periodensystem gibt die durchschnittliche Atommasse jedes Atoms an. Makroskopische Proben enthalten jedoch eine extrem große Anzahl von Atomen. Daher ist es unerlässlich, eine Zähleinheit namens Avogadro-Zahl zu verwenden.Die Avogadro-Zahl, ausgedrückt mit dem Symbol NA, wird normalerweise auf 6, 022 X 10^23 gerundet. Ihr Wert ist gleich der Anzahl der Atome in genau 12 Gramm des reinen Kohlenstoff-12 Isotops. Der Begriff Mol, abgekürzt mol, wird zur Beschreibung der Avogadro-Zahl verwendet, sowie der bekannte Begriff ein Dutzend zur Beschreibung einer Menge von 12 verwendet wird.Dennoch kann ein Dutzend verschiedener Elemente unterschiedlich schwer sein, obwohl sie die gleiche Anzahl von Elementen haben. Ebenso haben Mole von verschiedenen Elementen unterschiedliche Massen, enthalten aber immer die gleiche Anzahl von Atomen. Die Masse eines Mols von einem Element in Gramm wird als Stoffmenge bezeichnet und ausgedrückt in Gramm pro Mol.Ihr Wert entspricht numerisch der Atommasse des Elements. Daher erlaubt uns die Definition des Mols, die Teilchen durch Wiegen zu zählen. Die molare Masse und die Avogadro-Zahl können als Umrechnungsfaktoren verwendet werden.Dies kann zur Berechnung der Anzahl der Atome in einem 5 Gramm Goldbarren verwendet werden. Die durchschnittliche molare Masse von Gold beträgt 196, 96 Gramm pro Mol. Um die Masse in Mol umzuwandeln, dividiert man also die Masse des Barrens durch die durchschnittliche Stoffmenge und multipliziert dann die Menge der Mols mit der Avogadro-Zahl, um die Anzahl der Atome in der Probe zu erhalten.Dieser Goldbarren enthält also 1, 529 x 10^22 Atome.

molmasse

Die Identität einer Substanz wird nicht nur durch die darin enthaltenen Atom- oder Ionenarten definiert, sondern auch durch die Menge jeder Atom- oder Ionenart. Beispielsweise sind Wasser (H2O) und Wasserstoffperoxid (H2O2) insofern ähnlich, als ihre jeweiligen Moleküle aus Wasserstoff- und Sauerstoffatomen bestehen. Da ein Wasserstoffperoxidmolekül jedoch zwei Sauerstoffatome enthält, im Gegensatz zum Wassermolekül, das nur eines hat, weisen die beiden Substanzen sehr unterschiedliche Eigenschaften auf. Atome und Moleküle sind extrem klein. Daher ist zur Messung ihrer makroskopischen Mengen eine wissenschaftliche Standardeinheit erforderlich. Das Mol ist eine Mengeneinheit, die bekannten Einheiten wie Paar, Dutzend, Brutto usw. ähnelt. Es liefert ein spezifisches Maß für die Anzahl der Atome oder Moleküle in einer Stoffprobe. Die lateinische Konnotation für das Wort „Maulwurf“ ist „große Masse“ oder „Masse“, was mit seiner Verwendung als Name für diese Einheit übereinstimmt. Das Mol stellt eine Verbindung zwischen einer leicht messbaren makroskopischen Eigenschaft, der Massenmasse, und einer äußerst wichtigen Grundeigenschaft, der Anzahl der Atome, Moleküle usw., her. Ein Mol einer Substanz ist die Menge, in der es 6,02214076 × 1023 diskrete Einheiten (Atome oder Moleküle) gibt. Diese große Zahl, praktischerweise auf 6,022 × 1023 gerundet, ist eine Fundamentalkonstante, die als Avogadro-Zahl (NA) oder Avogadro-Konstante zu Ehren des italienischen Wissenschaftlers Amedeo Avogadro bekannt ist. Diese Konstante wird korrekt mit der expliziten Einheit „pro Mol“ angegeben. Gemäß seiner Definition als Mengeneinheit enthält 1 Mol eines Elements die gleiche Anzahl an Atomen wie 1 Mol eines anderen Elements. Die Massen von 1 Mol verschiedener Elemente sind jedoch unterschiedlich, da die Massen der einzelnen Atome drastisch unterschiedlich sind. Die Molmasse eines Elements (oder einer Verbindung) ist die Masse in Gramm von 1 Mol dieser Substanz, eine Eigenschaft, die in der Einheit Gramm pro Mol (g/mol) ausgedrückt wird. Die Molmasse einer Substanz entspricht numerisch ihrem Atom- oder Formelgewicht in amu. Gemäß der Amu-Definition wiegt ein einzelnes Kohlenstoffatom 12 amu (seine Atommasse beträgt 12 amu). Ein Mol Kohlenstoff wiegt 12 g (12 g C = 1 mol C-Atome = 6,022 × 1023 C-Atome), und die Molmasse von Kohlenstoff beträgt 12 g/mol. Diese Beziehung gilt für alle Elemente, da ihre Atommassen relativ zu denen der Amu-Referenzsubstanz Kohlenstoff-12 gemessen werden. In Erweiterung dieses Prinzips ist die Molmasse einer Verbindung in Gramm ebenfalls numerisch äquivalent zu ihrer Formelmasse in amu. Helium hat beispielsweise eine Atommasse von 4,002 amu und eine Molmasse von 4,002 g/mol. Während Atommasse und Molmasse numerisch gleichwertig sind, sollten Sie bedenken, dass sie sich in Bezug auf die Größenordnung stark unterscheiden. Um die enorme Größe des Maulwurfs zu erkennen, betrachten Sie einen kleinen Wassertropfen mit einem Gewicht von etwa 0,03 g. Obwohl dies nur einen winzigen Bruchteil von 1 Mol Wasser (~18 g) darstellt, enthält es mehr Wassermoleküle, als man sich vorstellen kann. Würden die Moleküle gleichmäßig auf die rund sieben Milliarden Menschen auf der Erde verteilt, bekäme jeder Mensch mehr als 100 Milliarden Wassermoleküle. Das Mol definiert den Zusammenhang zwischen Masse und Anzahl der Atome. Dadurch lässt sich die Anzahl der Atome anhand geeigneter Formen des Umrechnungsfaktors berechnen: 1 Mol Atome = 6,022 × 1023 Atome. Um zwischen der Masse eines Elements (in Gramm) und der Anzahl der Mol umzurechnen, wird die Molmasse des Elements (g/mol) als Umrechnungsfaktor verwendet. Dieser Text wurde angepasst von <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>

Molmasse

Die Identität einer Substanz wird nicht nur durch die Art der Atome oder Ionen definiert, die sie enthält, sondern auch durch die Menge der einzelnen Atome oder Ionen. Zum Beispiel...

Education

Lehre

JoVE Core

Chemie

Eins

Atoms and Elements

Atome und Elemente

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

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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atomic mass

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Average atomic mass explains why many elements on the periodic table have decimal values. Atoms are extremely small, so scientists use the atomic mass unit, or amu, to measure them. A carbon atom weighs less than 2 × 10−23 g, and the amu is defined from carbon-12. One amu is exactly 1/12 the mass of one carbon-12 atom, which is 1.6605 × 10−24 g. The dalton (Da) and the unified atomic mass unit (u) mean the same thing as the amu. For a single atom, atomic mass is usually close to its mass...

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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JoVE Core Chemie erweckt allgemeine Konzepte der Chemie durch kompakte und leicht verständliche animierte Videolektionen zum Leben. Außerdem zeigen wir in den Videos Wissenschaftler in Aktion bei klassischen und neuartigen Forschungsexperimenten, wie sie heutzutage in Laboren weltweit durchgeführt wurden.

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Ohio’s Learning Standards and Model Curriculum

Structure And Properties Of Matter

Quantifying matter

Interactions Of Matter

Stoichiometry

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CH.2

CH.2.a

CH.4

CH.4.a

Physical Science

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PS.4.a

Arizona Science Standards

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HS+C.P1

HS+C.P1U1.7

Texas Essential Knowledge and Skills

CHEM.8

CHEM.8.A

CHEM.11

CHEM.11.E

Alabama Course of Study Science

Matter and Its Interactions

9-12.C.1.1

Florida Department of Education

SC.912.P.8

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Chemistry and Physics

IPC.7

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Georgia Standards of Excellence

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The Mole Concept and Avogadro’s Number

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Mole, Mass, and Avogadro’s Number

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