Name: chemical formula mass and percent composition
Uploaded: 2020-09-03T13:38:26.000Z
Duration: 2 min 56 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.3.3

formula-mass-and-mole-concepts-of-compounds

Formula Mass and Mole Concepts of Compounds

화합물의 가장 작은 표현 단위는 화학식으로 묘사된 분자입니다. 화학식에 포함된 모든 원자의 원자량을 합하면 원자량 단위로 측정한 화합물의 분자 질량 이 됩니다. 예를 들어 자당이나 설탕의 분자량을 구하려면 각 원소의 원자량에 해당 원소의 원자 수를 곱합니다.

총 합이 자당의 분자량이 됩니다. 화합물 일 몰에 존재하는 모든 분자 의 질량을 몰 당 그램 단위로 측정한 것을 몰질량이라고 합니다. 화합물의 몰질량은 수치적으로 분자량(또는 화학식-질량)과 동일합니다.

예를 들어, 분자량이 342.3 원자량 단위인 자당은 몰질량이 몰 당 342.3 그램일 것입니다. 화학 물질에 존재하는 실제 분자나 입자의 수를 아는 것은 그 구성, 상호작용, 그리고 조합을 이해하는 데 필수적입니다. 그러나 주어진 화합물 표본을 가지고 일반적인 방법으로 실제 분자 수를 세는 것은 비현실적입니다.

몰질량과 몰, 아보가드로수 사이의 관계를 이용하여 존재하는 총 분자를 계산할 수 있습니다. 개념에 따르면 화합물의 몰질량은 6.022 곱하기 10의 23승 입자로 구성된 화합물 일 몰과 동일합니다. 따라서 342.3그램의 자당류에는6.022 곱하기 10의 23승개의 자당 분자가 포함됩니다.

예를 들어 자당 샘플의 무게가 150그램이라면 교차 곱하기 방법을 사용한 계산으로 분자의 수를 결정할 수 있습니다. 결과 150그램의 자당에는 2.63 곱하기 10의 23승개의 자당분자가 있습니다. 화합물 내 각 원소의 백분율은 질량-백분율 값을 사용하여 표시할 수 있습니다.

계산방법은 일 몰의 화합물에 있는 원소의 질량을 일 몰 화합물의 총 질량으로 나누고 백분율로 변환합니다. 실제로 자당에 있는 수소의 질량 백분율을 계산하기 위해 수소 원자의 총 질량과 자당 분자의 총 질량을 공식에 넣어 봅니다. 계산된 값은 자당이 6.4 질량 백분율의 수소를 함유하고 있음을 보여줍니다.

화합물의 공식 질량 및 몰 개념

공유결합 화합물의 공식 질량

화학 공식은 물질의 원소 구성을 나타냅니다. 공유결합 화합물의 경우, 공식은 물질의 단일 분자를 구성하는 원자의 수와 유형을 나타냅니다. 따라서 공식 질량은 분자 질량으로 올바르게 참조될 수 있습니다. 공유결합 화합물인 클로로포름(CHC_l3)의 분자식은 단일 분자가 탄소 원자 1개, 수소 원자 1개, 염소 원자 3개를 포함한다는 것을 나타냅니다. 클로로포름 분자의 평균 분자 질량은 다음 원자의 평균 원자 질량의 합과 같습니다.

<img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/1017/1017_Equations-01.png" style="height: 40px;" />

이온 화합물의 공식 질량

이온성 화합물은 전기적으로 중성인 벌크 물질을 생성하는 비율로 결합된 개별 양이온과 음이온으로 구성됩니다. 이온 화합물의 공식 질량은 공유 결합 화합물의 공식 질량과 동일한 방식으로 계산됩니다. 즉, 화합물의 공식에 있는 모든 원자의 평균 원자 질량을 합산합니다. 그러나 이온성 화합물의 공식은 개별 분자의 구성을 나타내지 않으므로 '분자량'으로 정확하게 지칭할 수 없습니다.

예를 들어, 일반 식용 소금 또는 염화나트륨(NaCl)은 나트륨 양이온(Na^+)과 염화물 음이온(Cl^-)이 1:1 비율로 결합된 이온 화합물입니다. 이 화합물의 공식 질량은 구성 요소의 평균 원자 질량을 더하여 계산됩니다.

<img alt="Eq2" src="https://www.jove.com/files/core/CDNSource/lessons/1017/1017_Equations-02.png" style="height: 40px;" />

이온 화합물의 공식 질량을 계산할 때 나트륨 양이온과 염화물 음이온의 질량 대신 중성 나트륨 및 염소 원자의 평균 질량이 사용되었습니다. 나트륨 양이온이 나트륨 원자보다 질량이 약간 작더라도(전자가 없기 때문에) 이 차이는 염화물 음이온이 염소 원자보다 약간 더 무겁다는 사실(추가 전자로 인해)로 상쇄됩니다. . 더욱이, 전자의 질량은 일반적인 원자의 질량에 비해 무시할 수 있을 정도로 작습니다.

질량 백분율 구성

화합물의 원소 구성은 그 화학적 정체성을 정의하며, 화학식은 이 원소 구성을 나타내는 가장 간결한 방법입니다. 화합물의 각 원소의 질량 백분율을 해당 특정 원소의 질량 백분율이라고 합니다. 조성 백분율은 각 원소의 질량을 화합물의 전체 질량으로 나눈 다음 백분율로 변환하여 계산할 수 있습니다.

백분율 조성은 알려진 공식의 다양한 화합물에서 특정 원소의 상대적 존재비를 평가하는 데 유용합니다. 해당 화합물의 분자식이나 실험식을 알고 있는 한, 조성 백분율은 화합물 원소의 원자 질량이나 몰 질량에서 파생될 수 있습니다.

예를 들어, 질산(HNO_3) 한 분자에는 14.01 amu의 질소 원자 1개, 1.008 amu의 수소 원자 1개, (3 × 16.00 amu) = 48.00 amu의 산소 원자 3개가 포함되어 있습니다. 따라서 질산의 공식 질량은 (14.01 amu + 1.008 amu + 48.00 amu) = 63.02 amu이며, 조성 비율은 다음과 같습니다.

<img alt="Eq3" src="https://www.jove.com/files/core/CDNSource/lessons/1017/1017_Equations-03.png" style="height: 40px;" />

<img alt="Eq4" src="https://www.jove.com/files/core/CDNSource/lessons/1017/1017_Equations-04.png" style="height: 40px;" />

<img alt="Eq5" src="https://www.jove.com/files/core/CDNSource/lessons/1017/1017_Equations-05.png" style="height: 40px;" />

이 문서는 에서 발췌되었습니다 <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> and <a href="https://openstax.org/books/chemistry-2e/pages/3-2-determining-empirical-and-molecular-formulas">Openstax, Chemistry 2e, Section 3.2: Determining Empirical and Molecular Formulas.</a>

공유 화합물의 공식 질량

화학식은 물질의 원소 구성을 나타냅니다. 공유 화합물의 경우, 공식은 ...

Education

교육

JoVE Core

화학

하나

Molecules, Compounds, and Chemical Equations

분자, 화합물 및 화학 방정식

molecules-compounds-and-chemical-equations

KEY TERMS AND CONCEPTS

주요 용어 및 개념

chemical formula mass and percent composition

Chemical formula mass and percent composition help describe the makeup of compounds. A chemical formula shows which atoms are present and how many of each atom appear in a substance.

For covalent compounds, the formula shows the atoms in one molecule. That is why formula mass can also be called molecular mass. Chloroform, CHCl3, is one example. Its formula shows one carbon atom, one hydrogen atom, and three chlorine atoms. The molecular mass is the sum of their average atomic masses.

Ionic compounds are different because they contain cations and anions that combine in ratios that make the bulk material electrically neutral. Their formula mass is found the same way, by adding the average atomic masses of the atoms in the formula. Sodium chloride, or table salt, is one example. Its formula, NaCl, shows sodium and chloride in a 1:1 ratio. For ionic compounds, the term molecular mass is not the best choice because the formula does not describe a single molecule.

When calculating formula mass for an ionic compound, neutral atom masses are used instead of ion masses. A sodium cation has slightly less mass than a sodium atom because it has lost an electron. A chloride anion has slightly more mass than a chlorine atom because it has gained an electron. The difference is small, and the mass of an electron is negligibly small compared with the mass of a typical atom.

Percent composition tells how much of a compound’s mass comes from each element. It is found by dividing the mass of each element by the total mass of the compound and converting the result to a percentage. This is useful for comparing the relative amount of an element in compounds with known formulas.

Nitric acid, HNO3, shows how the calculation works. One molecule contains one nitrogen atom with a mass of 14.01 amu, one hydrogen atom with a mass of 1.008 amu, and three oxygen atoms with a total mass of 48.00 amu. Its formula mass is 63.02 amu. From that total, the percent composition of each element can be determined.

Chemical Formula Mass and Percent Composition

chemical-formula-mass-and-percent-composition

molecules and compounds

Atomic Elements, Molecules, and Bonds

Matter is made of elements, and elements are built from atoms. An atom is the smallest unit of an element that still keeps that element’s properties. A silver coin, for example, is made of silver atoms. Each atom keeps the unique properties of silver. Elements are pure substances made of identical atoms. They cannot be broken down into simpler substances by chemical changes. Most elements are atomic elements, which use single atoms as their basic unit. Carbon and sodium are examples of atomic...

molecular models

Molecular Model Types in Chemistry

Molecular models help chemists and students visualize the structures and shapes of atoms and molecules. They represent the molecular architecture of chemical compounds in a way that is easier to study than formulas alone. Skeletal models are simple two-dimensional drawings of compounds. They show the molecular framework, or the bonds, without drawing every atom. In this model, many carbon and hydrogen atoms are not shown directly. Their positions are implied by the ends and junctions of the...

organic compounds

Organic Molecules in Everyday Chemistry

Organic molecules are carbon-based compounds found in living things and in many everyday products. Most organic compounds have carbon as the main element, bonded to hydrogen and other carbon atoms. Some carbon-containing substances, such as carbonates, cyanides, and simple oxides like CO and CO2, are not classified as organic. Carbon can form up to four strong bonds, which helps explain why organic compounds can make chains and rings of many sizes and shapes. These molecules appear in...

formula mass and mole concepts of compounds

Chemical formula mass and percent composition help describe the makeup of compounds. A chemical formula shows which atoms are present and how many of each atom appear in a substance. For covalent compounds, the formula shows the atoms in one molecule. That is why formula mass can also be called molecular mass. Chloroform, CHCl3, is one example. Its formula shows one carbon atom, one hydrogen atom, and three chlorine atoms. The molecular mass is the sum of their average atomic masses. Ionic...

experimental determination of chemical formula

experimental-determination-of-chemical-formula

Finding Empirical and Molecular Formulas

Chemical formulas show the elemental makeup of a compound. When a formula is unknown, scientists often start by measuring the masses of the elements in the sample. Those mass data are then used to find the simplest whole-number ratio of atoms, which gives the empirical formula. To get from mass to atom ratio, the masses of the elements are first converted to moles using molar masses. Chemical formulas describe numbers of atoms, not masses, so this step is necessary. In one example, 1.71 grams...

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Chemical equations show the identities and relative amounts of substances in a chemical reaction. The substances that react are called reactants, and their formulas are written on the left side of the equation. The substances formed are called products, and their formulas are written on the right side. A plus sign (+) separates formulas on the same side, and an arrow (→) shows the change from reactants to products. The numbers in a chemical equation are shown with coefficients. A coefficient...

key terms and concepts

Learn how to calculate formula mass for covalent and ionic compounds, then use it to find percent composition with examples like chloroform, salt, and nitric acid.

Chemical Formula Mass and Percent Composition | JoVE K12

chemistry

JoVE Core 화학은 간결하고 이해하기 쉬운 애니메이션을 통해 일반 화학 개념을 설명합니다. 또한, 과학자가 직접 고전실험과 연구실험을 진행하는 실사 영상을 제공합니다.

PS.Chm.4.3

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Ohio’s Learning Standards and Model Curriculum

Structure And Properties Of Matter

Quantifying matter

Interactions Of Matter

Stoichiometry

Tennessee Academic Standards

High School

Matter and Its Interactions

CHEM1.PS1.1

CHEM1.PS1.3

Virginia  Standards of Learning

HIgh School

CH.3

CH.3.a

CH.4

CH.4.a

Arizona Science Standards

Physical Science

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New Jersey Student Learning Standards for Science

HS-PS1-7

Texas Essential Knowledge and Skills

CHEM.7

CHEM.7.B

CHEM.8

CHEM.8.A

CHEM.8.B

CHEM.9

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Alabama Course of Study Science

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Florida Department of Education

SC.912.P.8

SC.912.P.8.7

SC.912.P.8.9

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New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-7.

Georgia Standards of Excellence

SC3.

The Mole Concept and Avogadro’s Number

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Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

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Atomic Mass

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Molar Mass

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Atomic Radii and Effective Nuclear Charge

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Construct an explanation to infer the atomic size, reactivity, electronegativity, and ionization energy of an element based on its position in the Periodic Table.

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Formal Charges

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	...

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PS.Chm.3.1

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Construct an explanation to summarize the influences intermolecular forces have on the properties of chemical compounds.

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Chemical Formula Mass and Percent Composition

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