Name: reading chemical equations and balancing them
Uploaded: 2020-09-03T13:38:26.000Z
Duration: 3 min 10 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.4.2

Chemical Equations

化学反応は 1つまたは複数の 物質が異なる物質に 化学的に変化することを 意味します 反応は従来 化学式を用いて 表現されています これは化学式を利用して 関係する原子 分子 または化合物を 表現する方法する方法です 反応の開始時に存在し 反応中に 消費される物質は 反応物と呼ばれます 反応物は式の左側に 記述されています 反応中に生成される物質は 生成物と呼ばれ 式の右側に記述されています 反応物と生成物を分ける矢印は 反応の方向を示しています 物質の状態の違いは 括弧付きの 略語を使って表現されています 化学反応には 質量保存の法則があり 反応に関与する すべての元素の総質量が 保存されます したがって 反応物と 生成物の両方において 各元素の累積原子数は 一致します 化学式は 反応に関与する実際の原子数を 反映させるために 数値係数を 使ってバランスをとります 化学式のバランスをとる際には 化合物の同一性を定義する 数値添字ではなく 数値係数のみを 変更することが重要です 一般的なガイドラインは 化学式を効率的に説明し 調整するのに役立ちます 例えば 液体の 安息香酸が燃焼して ガス状の二酸化炭素と 水を形成する場合 最初は骨格の化学反応式を 使用して表されます 次に 最初に化合物の中の 原子を調整し 次に自由元素の原子を調整して 原子のバランスを調整します 二酸化炭素と水の式の前に 係数7と3を含めることで 炭素原子と 水素原子のバランスを とることができます 15×2の分数係数は 酸素原子数を調整します 分数の係数は整数になるよう 式全体に分母を乗算 することにより整数に変換します 各要素の原子の合計数は バランスのとれた 方程式の両側で等しくなります イオン性化合物を含む 反応を表す化学式では 陽イオンが最初にバランスをとり その後に陰イオンが続きます 多原子イオンは常に1つの 単位としてバランスをとります 例えば硫酸アルミニウム水溶液は 水酸化カルシウム水溶液と反応し 固体の水酸化アルミニウムと 固体の硫酸カルシウムを 形成します 骨格方程式を使うと アルミニウムとカルシウムの 陽イオンがバランスし 多原子イオンの水酸化物と 硫酸イオンの陰イオンが続きます 最後に 係数を調整して 全体的にバランスの とれた式にします

化学方程式

化学方程式は、化学反応に関与する物質の固有性と相対的な量を表します。 反応する物質は反応物質と呼ばれ、その式は方程式の左側に置かれます。 反応によって生成される物質は生成物質と呼ばれ、その式は方程式の右側に配置されます。 プラス記号（ + ）は個々の反応物質と生成物質を分け、矢印（→）は反応物質側と生成物質側（右と左）を分けます。 反応物質と生成物質の相対的な数は、各式のすぐ左に配置された係数で表されます。 通常、係数 1 は表示しません。 可能な限り最小の整数の係数が化学式で一般的に使用され、比率として解釈されます。 たとえば、メタンと酸素は、二酸化炭素と水を 1:2:1:2 の比率で生成するように反応します。
 
 <img alt="Eq1" src="https://www.jovecore.com/CDNSource/lessons/1019/1019_Equations-01.png" style="height: 40px;" />
 
 この比率は、メタン、酸素、二酸化炭素、水の可能な最小係数がそれぞれ 1 、 2 、 1 、 2 であることを示しています。 係数は任意の量（数値）単位に関して解釈することができるため、この式は次のような多くの方法で正しく読むことができます。 
 
 ... 1 つのメタン分子と 2 つの酸素分子が反応して、 1 つの二酸化炭素分子と 2 つの水分子が生成されます。 
 
 II 1 モルのメタン分子と 2 モルの酸素分子が反応して、1 モルの二酸化炭素分子と2 モルの水分子が生成されます。  
 
 化学方程式中の反応物質および生成物の物理的状態は、数式の後に括弧で囲んだ省略形で示されることがあります。 標準的な略語には固体の場合は‘s’、液体の場合は‘l’ 、ガスの場合は‘g’ 、水に溶解した物質の場合は ‘aq’ が含まれます。 
 
 <h4>方程式のバランス </h4>
 
 バランスのとれた方程式では、反応に関与する各元素の原子数は反応物質側と生成物質側で同じであるため、質量保存の法則を満たすことができます。 バランスのとれた方程式は、矢印の両側の原子の数をそれぞれ加算し、これらの合計を比較して等しくなるようにすることで確認できます。 なお、元素の原子数は、その元素を含む式の係数に、その元素の添え字を掛けて算出します。 一つの元素が方程式の片側に複数の式で現れる場合、それぞれの式で表される原子の数を計算し、それを足し合わせる必要があります。 
 
 方程式のバランスをとるために、必要に応じて方程式の係数を変更できます。 化学方程式のバランスをとる過程で、整数ではなく分数を中間係数として使うと便利な場合があります。 バランスがとれたら、原子のバランスを崩すことなく、方程式のすべての係数に整数をかけて、小数の係数を整数に変換します。  
 
 例えば、酸素によるエタン（ C2H6 ）の反応により、水と二酸化炭素が生成されます。これは、次のアンバランスな方程式で表されます。 
 
 <img alt="Eq2" src="https://www.jovecore.com/CDNSource/lessons/1019/1019_Equations-02.png" style="height: 40px;" />
 
 アンバランスな式には以下が含まれる  
 
 <table style="margin-left: auto; margin-right: auto;">
 <tbody style="border: 1px solid black;">
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">原子 </td>
 <td style="color: black; border: 1px solid black; text-align: center;">反応物質 </td>
 <td style="color: black; border: 1px solid black; text-align: center;">生成物質 </td>
 <td style="color: black; border: 1px solid black; text-align: center;">バランスは？ </td>
 </tr>
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">C </td>
 <td style="color: black; border: 1px solid black; text-align: center;">2. </td>
 <td style="color: black; border: 1px solid black; text-align: center;">1. </td>
 <td style="color: black; border: 1px solid black; text-align: center;">いいえ </td>
 </tr>
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">H </td>
 <td style="color: black; border: 1px solid black; text-align: center;">6. </td>
 <td style="color: black; border: 1px solid black; text-align: center;">2. </td>
 <td style="color: black; border: 1px solid black; text-align: center;">いいえ </td>
 </tr>
 <tr>
 <td style="color: black; border: 1px solid black; text-align: center;">o </td>
 <td style="color: black; border: 1px solid black; text-align: center;">2. </td>
 <td style="color: black; border: 1px solid black; text-align: center;">3. </td>
 <td style="color: black; border: 1px solid black; text-align: center;">いいえ </td>
 </tr>
 </tbody>
 </table>
 
 炭素原子と水素原子の数のバランスをとるには、 CO2 に係数 2 を掛け、 H2O に係数 3 を掛けます。 これにより、生成物質の酸素原子の総数が 7 に変更されます。 酸素原子数のバランスをとるには、酸素に分数の係数 7/2 を掛けます。 反応物質と生成物質の係数を変更することにより、炭素、水素、および酸素原子の初期バランスを取ることで、一時的にバランスのとれた方程式が得られます。  
 
 <img alt="Eq3" src="https://www.jovecore.com/CDNSource/lessons/1019/1019_Equations-03.png" style="height: 40px;" />
 
 整数のみの係数を持つ従来の方程式は、各係数に 2 を乗算することで次のような式が得られます。 
 
 <img alt="Eq4" src="https://www.jovecore.com/CDNSource/lessons/1019/1019_Equations-04.png" style="height: 40px;" />
 
 このテキストは <a href="https://openstax.org/books/chemistry-2e/pages/4-1-writing-and-balancing-chemical-equations">、 Openstax 、 Chemistry 2e 、 Section 4.1: Writing and Balancing Chemical Equations から引用</a>しています。

化学方程式は、化学反応に関与する物質の同一性と相対量を表します。反応を起こしている物質は...

Education

JoVE Core

化学

Molecules, Compounds, and Chemical Equations

分子、化合物、および化学方程式

molecules-compounds-and-chemical-equations

KEY TERMS AND CONCEPTS

主要用語と概念

reading chemical equations and balancing them

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 is the number written in front of a formula. A coefficient of 1 is usually not written. The smallest whole-number coefficients are commonly used, and they work as ratios. For example, methane and oxygen react to form carbon dioxide and water in a 1:2:1:2 ratio.

That ratio can be read in more than one way. It can mean 1 methane molecule and 2 oxygen molecules make 1 carbon dioxide molecule and 2 water molecules. It can also mean 1 mole of methane molecules and 2 moles of oxygen molecules make 1 mole of carbon dioxide molecules and 2 moles of water molecules. Chemical equations may also include physical states after the formulas. Common state labels are s for solid, l for liquid, g for gas, and aq for substances dissolved in water.

A balanced chemical equation has the same number of atoms for each element on both sides. This follows the law of conservation of matter. To check balance, count the atoms on the reactant side and the product side and compare the totals. To find the number of atoms in a formula, multiply the coefficient by the subscript. If an element appears in more than one formula on one side, add all of those atoms together.

Balancing a chemical equation means changing coefficients, not the formulas themselves. Fractions can be used as temporary coefficients during balancing. For the reaction of ethane with oxygen, carbon and hydrogen are balanced first by placing 2 in front of carbon dioxide and 3 in front of water. That leaves 7 oxygen atoms on the product side, so oxygen gets a fractional coefficient of 7/2. The final equation is then multiplied by 2 to turn all coefficients into whole numbers without changing the balance.

Reading Chemical Equations and Balancing Them

reading-chemical-equations-and-balancing-them

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

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

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...

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...

chemical equations

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 read chemical equations, identify reactants and products, use coefficients and state symbols, and balance equations with whole-number ratios.

Reading Chemical Equations and Balancing Them | JoVE K12

chemistry

JoVE Core 化学は、簡潔で理解しやすいアニメーションビデオレッスンを使用して、一般的な化学の概念を生き生きとしたものにします。さらに、活動する科学者のビデオでは、現在世界中の実験室で行われている古典的そして独創的な研究・実験をお見せします。

Physical Science

PS.PSc.2.3

Pennsylvania State Academic Standards

Chemical Reactions

3.2.9-12.C

3.2.9-12.G

Louisiana Student Standards for Science

High School

Matter And Its Interactions

HS-PS1-2

HS-PS1-7

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Study Of Matter

Reactions of matter

Interactions Of Matter

Chemical reactions

Stoichiometry

Tennessee Academic Standards

Matter and Its Interactions

CHEM1.PS1.2

CHEM1.PS1.3

Virginia  Standards of Learning

HIgh School

CH.3

CH.3.a

CH.3.b

CH.3.c

PS.3

PS.3.d

Minnesota Academic Standards in Science

2.2.1 9C.1.2.1.2

Arizona Science Standards

HS+C.P1

HS+C.P1U1.5

HS+C.P1U1.7

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

Texas Essential Knowledge and Skills

CHEM.7

CHEM.7.B

CHEM.9

CHEM.9.A

Alabama Course of Study Science

9-12.PS.3.5.d

Next Generation Science Standards

Florida Department of Education

SC.912.P.8

SC.912.P.8.9

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

C-PS1-2

C-PS1-7

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-4.

HS-PS1-7.

HS-PS1-12.

Georgia Standards of Excellence

SPS3.

Chemical Reaction

SC3.

balancing-chemical-equations-and-reaction-outcomes

Balancing Chemical Equations and Reaction Outcomes

Scientific Laws and Theories

Scientific Laws

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The Scientific Method

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Classifying Matter by State

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Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Use models to explain how the scientific understanding of atomic structure has evolved.

PS.Chm.1.1

Radioactivity and Nuclear Equations

Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for ...

Types of Radioactivity

The most common types of radioactivity are &#945; decay, &#946; decay, &#947; decay, neutron emission, and electron capture.
Alpha (&#945;) decay is the ...

Nuclear Stability

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Nuclear Binding Energy

The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect ...

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger ...

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 ...

Nuclear Fusion

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Nuclear Transmutation

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Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

PS.Chm.1.2

Atomic Orbitals

An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution ...

The Pauli Exclusion Principle

The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that ...

The Energies of Atomic Orbitals

In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are ...

The Aufbau Principle and Hund's Rule

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electron-configuration-of-multielectron-atoms

Electron Configuration of Multielectron Atoms

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Molar Mass

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, ...

Use the Periodic Table as a model to predict the relative properties of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

PS.Chm.2.1

atomic-radii-and-effective-nuclear-charge

Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

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Ionization Energy

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Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

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

PS.Chm.2.2

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Lewis Symbols and the Octet Rule

Chemical bonds are complex interactions between two or more atoms or ions, which reduce the potential energy of the molecule. Gilbert N. Lewis developed a ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

The Born-Haber Cycle

Lattice Energy&#xA0;

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trends-in-lattice-energy-ion-size-and-charge

Trends in Lattice Energy: Ion Size and Charge

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Covalent Bonding and Lewis Structures

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Electronegativity

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Electronegativity values of ...

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Bond Polarity, Dipole Moment, and Percent Ionic Character

Bond Polarity

The absolute value of the difference in electronegativity (&Delta;EN) of two bonded atoms provides a rough measure of the polarity to be ...

Analyze and interpret data to explain the mechanisms and properties of the two main types of intramolecular (ionic and covalent) bonds.

PS.Chm.3.1

Analyze the structure of atoms and isotopes.

Reading Chemical Equations and Balancing Them

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