Chemistry
Chemical Equations
Chemical equations are symbolic representations of chemical reactions, showing the reactants and products involved. They use chemical formulas and symbols to depict the substances undergoing change. The equation must be balanced to satisfy the law of conservation of mass, ensuring that the same number of each type of atom is present on both sides of the equation.
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10 Key excerpts on "Chemical Equations"
eBook - PDF- Morris Hein, Susan Arena, Cary Willard(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
Charles D. Winters/Science Source Images I n the world today, we continually strive to express infor- mation in a concise, useful manner. From early child- hood, we are taught to translate our ideas and desires into sentences. In mathematics, we learn to describe numerical relationships and situations through mathemati- cal expressions and equations. Historians describe thou- sands of years of history in 500-page textbooks. Filmmakers translate entire events, such as the Olympics, into a few hours of entertainment. Chemists use Chemical Equations to describe reactions they observe in the laboratory or in nature. For example, as shown in the photo, flames and sparks result when aluminum foil is dropped into liquid bromine. Chemical Equations provide us with the means to (1) summarize the reaction, (2) display the substances that are reacting, (3) show the products, and (4) indicate the amounts of all component substances in a reaction. C H A P T E R O U T L I N E 8.1 The Chemical Equation 8.2 Writing and Balancing Chemical Equations 8.3 Why Do Chemical Reactions Occur? 8.4 Types of Chemical Equations 8.5 Heat in Chemical Reactions 8.6 Climate Change The Greenhouse Effect Chemical Equations 8 148 CHAPTER 8 • Chemical Equations 8.1 The Chemical Equation Describe the information present in a chemical equation. Chemical reactions always involve change. Atoms, molecules, or ions rearrange to form different substances, sometimes in a spectacular manner. For example, the thermite reac- tion is a reaction between aluminum metal and iron(III) oxide, which produces molten iron and aluminum oxide. The substances entering the reaction are called the reactants, and the substances formed are called the products. In our example, reactants aluminum iron(III) oxide products iron aluminum oxide During reactions, chemical bonds are broken and new bonds are formed. The reactants and products may be present as solids, liquids, gases, or in solution.
eBook - PDF- Morris Hein, Susan Arena, Cary Willard(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
155 Charles D. Winters/Science Source Images Charles D. Winters/Science Source In the world today, we continually strive to express information in a con- cise, useful manner. From early childhood, we are taught to translate our ideas and desires into sentences. In mathematics, we learn to describe numerical relationships and situations through mathematical expres- sions and equations. Historians describe thousands of years of history in 500-page textbooks. Filmmakers translate entire events, such as the Olympics, into a few hours of entertainment. Chemists use Chemical Equations to describe reactions they observe in the laboratory or in nature. For example, as shown in the photo, flames and sparks result when aluminum foil is dropped into liquid bro- mine. Chemical Equations provide us with the means to (1) summarize the reaction, (2) display the substances that are reacting, (3) show the products, and (4) indicate the amounts of all component substances in a reaction. CHAPTER OUTLINE 8.1 The Chemical Equation 8.2 Writing and Balancing Chemical Equations 8.3 Why Do Chemical Reactions Occur? 8.4 Types of Chemical Equations 8.5 Heat in Chemical Reactions 8.6 Climate Change: The Greenhouse Effect Chemical Equations CHAPTER 8 156 CHAPTER 8 Chemical Equations 8.1 The Chemical Equation LEARNING OBJECTIVE: Describe the information present in a chemical equation. Chemical reactions always involve change. Atoms, molecules, or ions rearrange to form dif- ferent substances, sometimes in a spectacular manner. For example, the thermite reaction is a reaction between aluminum metal and iron(III) oxide, which produces molten iron and aluminum oxide (see photo). The substances entering the reaction are called the reactants, and the substances formed are called the products. In our example, reactants aluminum iron(III) oxide products iron aluminum oxide During reactions, chemical bonds are broken and new bonds are formed.
- Morris Hein, Scott Pattison, Susan Arena, Leo R. Best(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
5.1 • Properties of Gases 143 Charles D. Winters/Photo Researchers 8.1 The Chemical Equation 8.2 Writing and Balancing Chemical Equations 8.3 Types of Chemical Equations 8.4 Heat in Chemical Reactions 8.5 Global Warming: The Greenhouse Effect Chemical Equations C H A P T E R 8 C H A P T E R O U T L I N E Flames and sparks result when aluminum foil is dropped into liquid bromine. I n the world today, we continually strive to express information in a concise, useful manner. From early childhood, we are taught to translate our ideas and desires into sentences. In mathematics, we learn to describe numerical relationships and situations through mathematical expressions and equations. Historians describe thousands of years of history in 500-page text- books. Filmmakers translate entire events, such as the Olympics, into a few hours of entertainment. Chemists use Chemical Equations to describe reactions they observe in the laboratory or in nature. Chemical Equations pro- vide us with the means to (1) summarize the reaction, (2) display the substances that are reacting, (3) show the products, and (4) indicate the amounts of all component substances in a reaction. 144 CHAPTER 8 • Chemical Equations TABLE 8.1 Symbols Commonly Used in Chemical Equations Symbol Meaning + Plus or added to (placed between substances) ¡ Yields; produces (points to products) (s) Solid state (written after a substance) (l) Liquid state (written after a substance) (g) Gaseous state (written after a substance) (aq) Aqueous solution (substance dissolved in water) Heat is added (when written above or below arrow) 8.1 THE CHEMICAL EQUATION Describe the information present in a chemical equation. Chemical reactions always involve change. Atoms, molecules, or ions rearrange to form dif- ferent substances, sometimes in a spectacular manner. For example, the thermite reaction is a reaction between aluminum metal and iron(III) oxide, which produces molten iron and alumi- num oxide.
eBook - PDF- Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
- 2015(Publication Date)
- Openstax(Publisher)
Chapter 4 | Stoichiometry of Chemical Reactions 173 4.1 Writing and Balancing Chemical Equations By the end of this section, you will be able to: • Derive Chemical Equations from narrative descriptions of chemical reactions. • Write and balance Chemical Equations in molecular, total ionic, and net ionic formats. The preceding chapter introduced the use of element symbols to represent individual atoms. When atoms gain or lose electrons to yield ions, or combine with other atoms to form molecules, their symbols are modified or combined to generate chemical formulas that appropriately represent these species. Extending this symbolism to represent both the identities and the relative quantities of substances undergoing a chemical (or physical) change involves writing and balancing a chemical equation. Consider as an example the reaction between one methane molecule (CH 4 ) and two diatomic oxygen molecules (O 2 ) to produce one carbon dioxide molecule (CO 2 ) and two water molecules (H 2 O). The chemical equation representing this process is provided in the upper half of Figure 4.2, with space-filling molecular models shown in the lower half of the figure. Figure 4.2 The reaction between methane and oxygen to yield carbon dioxide and water (shown at bottom) may be represented by a chemical equation using formulas (top). This example illustrates the fundamental aspects of any chemical equation: 1. The substances undergoing reaction are called reactants, and their formulas are placed on the left side of the equation. 2. The substances generated by the reaction are called products, and their formulas are placed on the right sight of the equation. 3. Plus signs (+) separate individual reactant and product formulas, and an arrow (⟶) separates the reactant and product (left and right) sides of the equation. 4. The relative numbers of reactant and product species are represented by coefficients (numbers placed immediately to the left of each formula).
eBook - PDF- Stanley E. Manahan(Author)
- 2009(Publication Date)
- CRC Press(Publisher)
To a very large extent, chemistry is the study other operation involving chemicals. To a very large extent, chemistry is the study of chemical reactions expressed on paper as Chemical Equations. A of chemical reactions expressed on paper as Chemical Equations. A chemical chemical equation equation is a sentence of chemistry, made up of words consisting of chemical is a sentence of chemistry, made up of words consisting of chemical formulas. A sentence should be put together according to rules understood by all formulas. A sentence should be put together according to rules understood by all those literate in the language. The rules of the chemical language are particularly those literate in the language. The rules of the chemical language are particularly rigorous. Although a grammatically sloppy sentence in a spoken language can still rigorous. Although a grammatically sloppy sentence in a spoken language can still 182 Fundamentals of Sustainable Chemical Science 182 Fundamentals of Sustainable Chemical Science convey a meaningful message, a chemical equation with even a small error is convey a meaningful message, a chemical equation with even a small error is misleading and often meaningless. misleading and often meaningless. Quantitative Calculations from Chemical Equations Quantitative Calculations from Chemical Equations Chemistry is a quantitative science, and it is important to know how to do some Chemistry is a quantitative science, and it is important to know how to do some of the basic chemical calculations early in a beginning chemistry course. Among the of the basic chemical calculations early in a beginning chemistry course. Among the most important of these are the calculations of the quantities of substances consumed most important of these are the calculations of the quantities of substances consumed or produced in a chemical reaction. Such calculations are classified as or produced in a chemical reaction.
eBook - PDF- John Kenkel(Author)
- 2010(Publication Date)
- CRC Press(Publisher)
These symbols and formulas provide a type of chemical shorthand that chemists have found invaluable because of their convenience . Even if you have found the task of learning symbols, formulas, and names to be laborious, ultimately this work reaps the important reward of convenience . The use of symbols and formulas is especially helpful in the expression of chemical change . Another term for chemical change, or the transforma-tion of one or more substances with known properties into one or more other substances with completely different properties, is chemical reaction . The chemical combination of hydrogen and oxygen to form water is an example of a chemical reaction . We say that hydrogen and oxygen react to form water, or that hydrogen reacts with oxygen to form water . A statement of a chemical reaction that uses the convenient chemical shorthand of symbols and formulas is known as a chemical equation . In a chemical equation, the symbols and for-mulas of the substances present before the reaction takes place are written to the left and separated by a plus (+) sign . An arrow pointing to the right signi-fies a chemical change . Symbols and formulas of the elements or compounds that form as a result of the reaction appear on the right . These are also sepa-rated by + signs . Thus, for the water formation reaction, we would write: H 2 + O 2 → H 2 O The substance or substances to the left of the arrow, the H 2 and the O 2 in the example, are called the reactants . The substance or substances to the right of 193 Chemical Equations and Stoichiometry the arrow, water in this example, are called the products of the reaction . Thus, we have reactants and products separated by the arrow . Reactants → Products The information in a chemical equation is verbalized by using the words plus or and or reacts with for the + signs on the left; the words yields or reacts to produce or to form for the arrow; and the word plus or and for the + signs on the right .
eBook - PDF- Edward J. Neth, Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
- 2019(Publication Date)
- Openstax(Publisher)
(credit: modification of work by NASA) CHAPTER OUTLINE 7.1 Writing and Balancing Chemical Equations LEARNING OBJECTIVES By the end of this section, you will be able to: • Derive Chemical Equations from narrative descriptions of chemical reactions. • Write and balance Chemical Equations in molecular, total ionic, and net ionic formats. An earlier chapter of this text introduced the use of element symbols to represent individual atoms. When atoms gain or lose electrons to yield ions, or combine with other atoms to form molecules, their symbols are modified or combined to generate chemical formulas that appropriately represent these species. Extending this symbolism to represent both the identities and the relative quantities of substances undergoing a chemical (or physical) change involves writing and balancing a chemical equation. Consider as an example the reaction between one methane molecule (CH 4 ) and two diatomic oxygen molecules (O 2 ) to produce one carbon dioxide molecule (CO 2 ) and two water molecules (H 2 O). The chemical equation representing this process is provided in the upper half of Figure 7.2, with space-filling molecular models shown in the lower half of the figure. FIGURE 7.2 The reaction between methane and oxygen to yield carbon dioxide and water (shown at bottom) may be represented by a chemical equation using formulas (top). This example illustrates the fundamental aspects of any chemical equation: 1. The substances undergoing reaction are called reactants, and their formulas are placed on the left side of the equation. 2. The substances generated by the reaction are called products, and their formulas are placed on the right side of the equation. 3. Plus signs (+) separate individual reactant and product formulas, and an arrow separates the reactant and product (left and right) sides of the equation.
eBook - PDF- Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
- 2019(Publication Date)
- Openstax(Publisher)
(credit: modification of work by NASA) CHAPTER OUTLINE 4.1 Writing and Balancing Chemical Equations LEARNING OBJECTIVES By the end of this section, you will be able to: • Derive Chemical Equations from narrative descriptions of chemical reactions. • Write and balance Chemical Equations in molecular, total ionic, and net ionic formats. An earlier chapter of this text introduced the use of element symbols to represent individual atoms. When atoms gain or lose electrons to yield ions, or combine with other atoms to form molecules, their symbols are modified or combined to generate chemical formulas that appropriately represent these species. Extending this symbolism to represent both the identities and the relative quantities of substances undergoing a chemical (or physical) change involves writing and balancing a chemical equation. Consider as an example the reaction between one methane molecule (CH 4 ) and two diatomic oxygen molecules (O 2 ) to produce one carbon dioxide molecule (CO 2 ) and two water molecules (H 2 O). The chemical equation representing this process is provided in the upper half of Figure 4.2, with space-filling molecular models shown in the lower half of the figure. FIGURE 4.2 The reaction between methane and oxygen to yield carbon dioxide and water (shown at bottom) may be represented by a chemical equation using formulas (top). This example illustrates the fundamental aspects of any chemical equation: 1. The substances undergoing reaction are called reactants, and their formulas are placed on the left side of the equation. 2. The substances generated by the reaction are called products, and their formulas are placed on the right side of the equation. 3. Plus signs (+) separate individual reactant and product formulas, and an arrow separates the reactant and product (left and right) sides of the equation.
eBook - PDFChemistry for Today
General, Organic, and Biochemistry
- Spencer Seager, Michael Slabaugh, Maren Hansen, , Spencer Seager, Spencer Seager, Michael Slabaugh, Maren Hansen(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
Thus, atoms are conserved in chemical reactions, but molecules are not. The numbers written as coefficients to the left of the molecular formulas make the equa- tion consistent with this law by making the total number of each kind of atom equal in the reactants and products. Note that coefficients of 1 are never written but are understood. Equations written this way are said to be balanced. In addition, the symbol in parentheses to the right of each formula indicates the state or form in which the substance exists. Thus, in Equation 5.2, the reactants hydrogen and oxygen (see Figure 5.2) are both in the form of gases (g), and the product water is in the form of a liquid (/). Other common symbols you will encounter are (s) to designate a solid and (aq) to designate a substance dissolved in water. The symbol (aq) comes from the first two letters of aqua, the Latin word for water. reactants of a reaction The substances that undergo chemical change during the reaction. They are written on the left side of the equation, representing the reaction. products of a reaction The substances produced as a result of the reaction taking place. They are written on the right side of the equation, representing the reaction. law of conservation of matter Atoms are neither created nor destroyed in chemical reactions. balanced equation An equation in which the number of atoms of each element in the reactants is the same as the number of atoms of that same element in the products. FIGURE 5.1 Liquid hydrogen in combination with liquid oxygen yields the highest efficiency of any known rocket propellant. Here, a space shuttle is shown about 5 seconds before launch, after the hydrogen-burning main engines have ignited but before the solid rocket boosters begin firing. Darryl Fonseka/Shutterstock.com Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.
eBook - PDFIntroductory Chemistry
An Active Learning Approach
- Mark Cracolice, Edward Peters, Mark Cracolice(Authors)
- 2020(Publication Date)
- Cengage Learning EMEA(Publisher)
8.5 Interpreting Chemical Equations Goal 4 Given a balanced chemical equation or information from which it can be written, describe its meaning on the particulate, molar, and macroscopic levels. In the previous two sections, you learned that a chemical equation contains a great deal of information. First, it gives a qualitative description of a reaction. The equa- tion 2 H 2 sgd 1 O 2 sgd S 2 H 2 Osgd says that hydrogen reacts with oxygen to form water and that both reactants and the product are in the gas phase. Second, the equation gives quantitative information about the reaction. You can interpret this quantitative information on a number of different levels. We stated earlier that standard practice is to write equations with the lowest whole-number coefficients possible. This is because equations are often interpreted on the particulate level. Thus, 2 H 2 sgd 1 O 2 sgd S 2 H 2 Osgd means “two molecules of hydrogen react with one oxygen molecule to form two water molecules.” The sym- bols in the equation represent the particles, shown in Figure 8.11 as space-filling models. We can scale up our particulate interpretation to any desired multiple of the coefficients in the balanced equation. We can think of the equation in terms of doz- ens. For example, “two dozen molecules of hydrogen react with one dozen oxygen molecules to form two dozen water molecules” (Figure 8.12). Copyright 2021 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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