Chemistry
Representing Chemical Reactions
Representing chemical reactions involves using chemical equations to depict the reactants and products involved in a chemical change. These equations show the balanced stoichiometry of the reaction, with the number of atoms of each element being conserved. Symbols such as arrows and plus signs are used to indicate the direction and combination of the reactants and products.
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7 Key excerpts on "Representing Chemical Reactions"
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- 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 - 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- Leo J. Malone, Theodore O. Dolter(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
The species formed as a result of the reaction are to the right of the arrow and are called the products. In this format, note that the phrase combines with (or reacts with) is represented by a plus sign (+). When there is more than one reactant or product, the symbols or formulas on each side of the equation are separated by a +. The word produces (or yields) may be represented by an arrow (¡). Note in Table 6-1 that there are other representations for the yield sign, depending on the situation. The chemical equation shown above tells us only about the elements involved. However, we know more information than just the elements involved. First, if an ele- ment exists as molecules under normal conditions, then the formula of the molecule is shown. Recall from Chapter 4 that both hydrogen and oxygen exist as diatomic molecules under normal conditions. Including this information, the equation is H 2 + O 2 ¡ H 2 O reactants products An important duty of a chemical equation is to demonstrate faithfully the law of conservation of mass, which states that mass can be neither created nor destroyed. In Dalton’s atomic theory, this law was explained for chemical reactions. He suggested that reactions are simply rearrangements of the same number of atoms. A close look at the equation above shows that there are two oxygen atoms on the left but only one on the right. To conform to the law of conservation of mass, an equation C C OBJECTIVE FOR SECTION 6-1 Write balanced chemical equations for simple reac- tions from inspection. OBJECTIVES 6-1 Write balanced chemical equations for simple reactions from inspection. 6-2 Classify certain chemical reactions as being combustion, combination, or decomposition reactions. SETTING A GOAL ■ n You will begin to use the symbolic language of chemistry by writing balanced chemical equations for several identifiable reaction types. Part A The Representation of Chemical Changes and Three Types of Changes
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)
(Section 5.7) 5 Classify reactions as exothermic or endothermic. (Section 5.8) 6 Use the mole concept to do calculations based on chemical reaction equations. (Section 5.9) 7 Use the mole concept to do calculations based on the limiting-reactant principle. (Section 5.10) 8 Use the mole concept to do percentage-yield calculations. (Section 5.11) Nastasic/E+/Getty Images Copyright 2022 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. Chemical Reactions 139 IN PREVIOUS CHAPTERS, we introduced the terms molecule, element, com- pound, and chemical change. In Chapter 1, you learned that chemical changes result in the transformation of one or more substances into one or more new substances. The processes involved in such changes are called chemical reactions. In this chapter, you will learn to write and read chemical equations that represent chemical reac- tions, to classify reactions, and to do calculations based on the application of the mole concept to chemical equations. 5.1 Chemical Equations Learning Objective 1 Identify the reactants and products in written reaction equations, and balance the equations by inspection. A simple chemical reaction between elemental hydrogen and oxygen has been used to power the engines of a number of spacecraft, including the space shuttle, which was oper- ated by the United States from 1981 to 2011 (see Figure 5.1). The products are water and much heat. For the moment, we will focus only on the substances involved; we will deal with the heat later.
eBook - PDF- Stanley E. Manahan(Author)
- 2009(Publication Date)
- CRC Press(Publisher)
These are designated by . These are designated by chemical chemical formulas formulas consisting of symbols for the kinds of atoms in the compound and subscripts consisting of symbols for the kinds of atoms in the compound and subscripts indicating the relative numbers of atoms of each kind in the compound. In chemical indicating the relative numbers of atoms of each kind in the compound. In chemical language, the symbols of the elements are the letters of the chemical alphabet and language, the symbols of the elements are the letters of the chemical alphabet and the formulas are the words of chemistry. the formulas are the words of chemistry. Chemical Reactions and Equations: The Sentences of the Chemical Reactions and Equations: The Sentences of the Chemical Language Chemical Language The formation of chemical compounds, their decomposition, and their interac-The formation of chemical compounds, their decomposition, and their interac-tions with one another fall under the category of tions with one another fall under the category of chemical reactions chemical reactions . Chemical . Chemical reactions are involved in the annual production of millions of kilograms of indus-reactions are involved in the annual production of millions of kilograms of indus-trial chemicals, bacterially mediated degradation of water pollutants, the chemical trial chemicals, bacterially mediated degradation of water pollutants, the chemical analysis of the kinds and quantities of components of a sample, and practically any analysis of the kinds and quantities of components of a sample, and practically any other operation involving chemicals. 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.
eBook - PDF- David A. Ucko(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
You are already familiar with some chemical re-actions. The rusting of iron, the burning of wood, and the digesting of food all involve chemical change. All compounds are formed by chemical reactions. The same com-pound can be formed by several different chemical reactions. But re-gardless of how a particular compound is made, its composition is always the same. This observation is summarized by the law of definite 250 CHEMICAL REACTIONS / 9.2 CHEMICAL EQUATIONS proportions: a given compound always contains its component ele-ments in fixed proportions by weight. The law, illustrated in the dis-cussion of percentage composition in Section 8.6, follows from the atomic theory. A compound consists of molecules or formula units, which are fixed combinations of atoms or ions, joined by bonds formed through a chemical reaction. For example, the compound water con-sists of molecules of H 2 0 . No matter how water is made or where it is found, it always contains two hydrogen atoms for every one oxygen atom. Mixtures, on the other hand, consist of substances that have not reacted with each other. There are no chemical bonds formed between the components in a mixture, and the mixture's composition therefore is not fixed. 9.2 A chemical equation is a shorthand representation of a chemical re-CHEMICAL action. Using the formulas of the substances involved in the reaction, EQUATIONS the chemical equation summarizes the chemical change that takes place. We can think of chemical equations as chemical sentences. We write them by following certain rules, just as we do when we write sentences in English (see Figure 9-2). The equation for the reaction of iron and sulfur is: Fe^j_S FeS reactants product The starting substances, called reactants, are separated from the new substance, called the product, by an arrow. The arrow shows the di-rection of chemical change by pointing from the reactants to the prod-ucts.
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