Name: mole, mass, and avogadro’s number
Uploaded: 2020-09-03T13:38:25.000Z
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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

Het periodiek systeem geeft de gemiddelde atoommassa van elk atoom. Macroscopische monsters bevatten echter extreem grote aantallen atomen. Daarom is het essentieel om een teleenheid te gebruiken die het getal van Avogadro wordt genoemd.Het getal van Avogadro, uitgedrukt als het symbool NA, wordt meestal afgerond op 6, 022 X 10^23. De waarde is gelijk aan het aantal atomen in precies 12 gram zuivere koolstof-12 isotoop. De term mol, afgekort mol, wordt gebruikt om het getal van Avogadro te beschrijven, net zoals de bekende term dozijn wordt gebruikt om een aantal van 12 te beschrijven.Desalniettemin kunnen een dozijn verschillende items verschillend wegen ondanks dat ze hetzelfde aantal items hebben. Op dezelfde manier hebben mollen van verschillende elementen verschillende massa's, maar bevatten ze altijd hetzelfde aantal atomen. De massa in gram van een mol van een element wordt de molaire massa genoemd, uitgedrukt in gram per mol.De waarde is numeriek gelijk aan de atomaire massa van het element. Daarom kunnen we met de definitie van de mol deeltjes tellen door ze te wegen. De molaire massa en het getal van Avogadro kunnen als omrekeningsfactoren worden gebruikt.Dit kan worden gebruikt om het aantal atomen in een goudstaaf van 5 gram te berekenen. De gemiddelde molaire massa van goud is 196, 96 gram per mol. Om de massa in mollen om te zetten, deel je de massa van de staaf door de gemiddelde molmassa.Vermenigvuldig vervolgens het aantal mollen met het getal van de Avogadro om het totale aantal atomen in het monster te krijgen. Deze staaf goud bevat dus 1, 529 X 10^22 atomen.

molaire massa

De identiteit van een stof wordt niet alleen bepaald door de soort atomen of ionen die deze bevat, maar ook door de hoeveelheid van elk type atoom of ion. Water, H2O, en waterstofperoxide, H2O2, zijn bijvoorbeeld hetzelfde omdat hun respectieve moleculen zijn samengesteld uit waterstof- en zuurstofatomen. Omdat een waterstofperoxidemolecuul echter twee zuurstofatomen bevat, in tegenstelling tot het watermolecuul, dat er maar één heeft, vertonen de twee stoffen zeer verschillende eigenschappen. Atomen en moleculen zijn extreem klein, waardoor een gestandaardiseerde eenheid nodig is om hun macroscopische hoeveelheden te meten.De mol is een hoeveelheidseenheid die lijkt op bekende eenheden zoals paar, dozijn, bruto, enz. Het geeft een specifieke maatstaf voor het aantal atomen of moleculen in een materiemonster. De Latijnse connotatie voor het woord ‘mol’ is ‘grote massa’ of ‘bulk’, wat consistent is met het gebruik ervan als naam voor deze eenheid. De mol vormt een verband tussen een gemakkelijk te meten macroscopische eigenschap, de bulkmassa, en een uiterst belangrijke fundamentele eigenschap, het aantal atomen, moleculen, enzovoort. Een mol van een stof is de hoeveelheid waarin er 6,02214076 x 1023 afzonderlijke entiteiten (atomen of moleculen) zijn. Dit grote getal, handig afgerond op 6,022 x 1023, is een fundamentele constante die bekend staat als het getal van Avogadro (NA) of de constante van Avogadro ter ere van de Italiaanse wetenschapper Amedeo Avogadro. Deze constante wordt correct gerapporteerd met de expliciete eenheid ‘per mol’. In overeenstemming met de definitie ervan als een hoeveelheidseenheid, bevat 1 mol van een element hetzelfde aantal atomen als 1 mol van een ander element. De massa's van 1 mol verschillende elementen zijn echter verschillend, omdat de massa's van de individuele atomen drastisch verschillend zijn. De molaire massa van een element (of verbinding) is de massa in grammen van 1 mol van die stof, een eigenschap uitgedrukt in eenheden van gram per mol (g/mol). De molaire massa van elke stof is numeriek equivalent aan het atoom- of formulegewicht in amu. Volgens de amu-definitie weegt een enkel koolstofatoom 12 amu (de atoommassa is 12 amu). Een mol koolstof weegt 12 g (12 g C = 1 mol C-atomen = 6,022 × 1023 C-atomen) en de molaire massa van koolstof is 12 g/mol. Deze relatie geldt voor alle elementen, aangezien hun atomaire massa wordt gemeten ten opzichte van die van de amu-referentiesubstantie, koolstof-12. Als we dit principe uitbreiden, is de molaire massa van een verbinding in grammen eveneens numeriek equivalent aan de massa in de formule in amu. Helium heeft bijvoorbeeld een atoommassa van 4,002 amu en een molaire massa van 4,002 g/mol. Hoewel de atoommassa en de molaire massa numeriek equivalent zijn, moet je er rekening mee houden dat ze qua schaal enorm van elkaar verschillen. Om de enorme omvang van de mol te kunnen waarderen, moet je een kleine druppel water overwegen die ongeveer 0,03 g weegt. Hoewel dit slechts een kleine fractie van 1 mol water (~18 g) vertegenwoordigt, bevat het meer watermoleculen dan men zich kan voorstellen. Als de moleculen gelijk verdeeld zouden zijn over de grofweg zeven miljard mensen op aarde, zou ieder mens ruim 100 miljard moleculen water ontvangen. De mol definieert de relatie tussen massa en het aantal atomen. Hierdoor kan het aantal atomen worden berekend op basis van geschikte vormen van de conversiefactor: 1 mol atomen = 6,022 x 1023 atomen. Om de massa van een element (in gram) en het aantal mol om te rekenen, wordt de molaire massa van het element (g/mol) als conversiefactor gebruikt. Text adapted from <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>

Molaire massa

The identity of a substance is defined not only by the types of atoms or ions it contains but by the quantity of each type of atom or ion. For example, ...

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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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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 ×...

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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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Structure And Properties Of Matter

Quantifying matter

Interactions Of Matter

Stoichiometry

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CH.4

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CHEM.11

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Mole, Mass, and Avogadro’s Number

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