Chemistry
Writing Chemical Formulae
Writing chemical formulae involves representing the composition of a compound using chemical symbols and numerical subscripts. This allows for a concise and standardized way to communicate the elements and their respective ratios within a substance. The formula provides important information about the types and quantities of atoms present in a compound.
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8 Key excerpts on "Writing Chemical Formulae"
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- Morris Hein, Judith N. Peisen, Robert L. Miner(Authors)
- 2013(Publication Date)
- Wiley(Publisher)
Writing Equations A chemical change or reaction results in the formation of products whose compositions are different from the starting substances (reactants). A chemical equation is a shorthand expression for a chemical reaction. Substances in the equation are represented by their for- mulas. The equation indicates both the reactants and their products. The reactants are writ- ten on the left side and the products on the right side of the equation. An arrow point- ing to the products separates the reactants from the products. A plus sign () is used to separate one reactant (or product) from another. Often, a phase label is added after each formula to indicate the phase of the reactant or product represented by the formula. The phase labels are: (s) solid; (l) liquid; (g) gas; (aq) aqueous. Reactants ¡ Products ( ¡ ) Example 1. The combustion of magnesium in oxygen or air. Word equation: Formula equation: (unbalanced) Phase labels included: (unbalanced) Example 2. Barium chloride and sulfuric acid solutions are mixed Word equation: Formula equation: (unbalanced) Phase labels included: (unbalanced) Example 3. Hydrochloric acid is added to sodium carbonate Word equation: Formula equation: (unbalanced) Phase labels included: (unbalanced) C. Balancing Equations There is no detectable change in mass resulting from a chemical reaction. Therefore, the mass of the products must equal the mass of the reactants before the chemical change occurred. In representing the chemical change by an equation, this conservation of mass is attained by “balancing the equation”. Because each atom has a particular mass, we balance an equa- tion by adjusting the number of atoms of each kind of element to be the same on each side of the equation. This adjustment is never made by changing subscripts in correct formulas.
eBook - PDF- David A. Ucko(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
SEVEN Writing names and formulas of compounds In Chapter Seven we describe how the composition of a chemical compound can be represented in two ways: by its formula and by its name. Systematic methods are presented for naming covalent and ionic compounds based on the number and type of atoms or ions in the molecule or formula unit. A method for predicting the formulas of ionic compounds is illustrated. Examples of compounds and their uses are given. To demonstrate an understanding of Chapter Seven you should be able to: 1 Write the names and formulas of covalent compounds. 2 Write the names and formulas of simple ionic compounds. 3 Write the names and formulas of compounds involving polyatomic ions. 4 Predict the formulas of ionic compounds, given the elements or ions from which they form. 5 Write the names and formulas of common acids. 6 Give an example of an important chemical compound for each main group. 7.1 Covalent compounds containing only two elements are called binary COVALENT compounds. When we write the name or formula of a binary covalent COMPOUNDS compound we place the two elements in order of increasing electro-negativity. The name or symbol of the more electronegative element is written last. The order of the elements is shown by the following list: B Si C Sb As P N H Se S I Br CI O F > order of elements in binary covalent compounds 185
eBook - PDF- Allan Blackman, Steven E. Bottle, Siegbert Schmid, Mauro Mocerino, Uta Wille(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
It may be as simple as water, H 2 O, or as complicated as C 30 H 34 AuBClF 3 N 6 O 2 P 2 PtW, the compound which currently holds the record for containing the most elements. As we have seen in the introductory chapter on the atom, each chemical element is described by a one- or two-letter symbol, and these form the basis for all chemical formulae. The simplest chemical formulae describe pure elements and are usually just their elemental symbols as listed on the periodic table; for example, helium is He, silicon is Si and copper is Cu. Such formulae imply that the bulk elements are composed of either individual atoms which do not interact (such as He) or ‘infinite’ three-dimensional arrays of bonded atoms (such as Si and Cu). However, this is not the case for some elements, and we must write more complex chemical formulae for these. For example, seven elements (hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine) occur naturally neither as individual atoms nor as three-dimensional arrays but as molecules containing two atoms (diatomic molecules). To signify this, their chemical formulae are written as H 2 , N 2 , O 2 , F 2 , Cl 2 , Br 2 and I 2 , respectively. Some other elements occur as larger molecules; a phosphorus molecule contains four P atoms and a sulfur molecule contains eight S atoms so their chemical formulae are P 4 and S 8 , respectively. A chemical formula that refers to a discrete molecule is often called a molecular formula as it describes the types and numbers of atoms present in the molecule. Note that a subscripted numeral refers to the atom immediately preceding it, or, if it follows a group of atoms enclosed in parentheses, to the entire group of enclosed atoms. For example, the chemical formula BH 3 shows that the compound contains one boron atom and three hydrogen atoms, whereas the chemical formula B(OH) 3 shows that the compound contains one boron atom, three oxygen atoms and three hydrogen atoms.
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 - PDFChemoinformatics
A Textbook
- Johann Gasteiger, Thomas Engel(Authors)
- 2006(Publication Date)
- Wiley-VCH(Publisher)
[1]. In chemistry, chemical structures have to be represented in machine-readable form by scientific, artificial languages (see Figure 2-2). Four basic approaches are introduced in the following sections: trivial nomenclature; systematic nomen- clature; chemical notation; and mathematical notation of chemical structures. Before discussing the different ways of representing a chemical compound, some terms have to be defined concerning the reproducibility or transformation of structures and notations. 16 2.1 Introduction The major significance of chemical nomenclature or notation systems is that they denote compounds in order to reproduce and transfer them from one coding to another, according to the intended application. As each coding may not include all the pieces of information in the other coding, or may have interpretable coding rules, the transformation is not always unambiguous and unique. A nomenclature or notation is called unambiguous if it produces only one struc- ture. However, the structure could be expressed in this nomenclature or notation by more than one representation, all producing the same structure. Moreover, “uniqueness” demands that the transformation results in only one – unique – structure or nomenclature, respectively, in both directions. 17 2 Representation of Chemical Compounds Figure 2-1. Hierarchical scheme for representations of a molecule with different contents of structural information. 2.2 Chemical Nomenclature Nomenclature is the compilation of descriptions of things and technical terms in a special field of knowledge, the vocabulary of a technical language. In the history of chemistry, a systematic nomenclature became significant only rather late. In the early times of alchemy, the properties of the substance or its appearance played a major role in giving a compound a name. Libavius was the first person who tried to fix some kind of nomenclature in Alchemia in 1597.
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.
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