Chemical Calculations
Chemical calculations involve using mathematical principles to determine quantities of substances involved in chemical reactions. This includes stoichiometry, which involves calculating the amount of reactants and products in a chemical reaction, as well as determining the concentration of solutions and performing various types of chemical conversions. These calculations are essential for understanding and predicting chemical reactions.
3 Key excerpts on "Chemical Calculations"
eBook - ePub- Jeffrey Gaffney, Nancy Marley(Authors)
- 2017(Publication Date)
- Elsevier(Publisher)
...Chapter 4 Chemical Equations and Mass Balance Abstract This chapter introduces stoichiometry beginning with the mole concept and using Avogadro’s number as a conversion factor between the number of moles and the number of fundamental units in a substance. Case studies are used to present the determination of the empirical and molecular formulas from experimental data. Methods for balancing chemical equations and determining the limiting reactant are covered. The difference between percent yield and atom economy in chemical reactions is discussed in terms of determining the most economical and greener processes, using the steel industry as a Case Study. The process controlling the aqueous solubility of ionic compounds and their influences on precipitation reactions is discussed. The determination of the concentration of aqueous solutions in molarity is also covered. Keywords Mole; Empirical formula; Chemical equations; Stoichiometry; Limiting reactant; Percent yield; Spectator ions; Solubility; Precipitation reactions; Molarity Outline 4.1 The Mole 4.2 The Empirical Formula 4.3 Chemical Equations 4.4 Stoichiometry 4.5 Limiting Reactant and Percent Yield 4.6 Aqueous Solubility of Ionic Compounds 4.7 Precipitation Reactions in Aqueous Solution 4.8 Concentrations in Aqueous Solution Study Questions Problems 4.1 The Mole Since chemistry deals with the properties of individual atoms and molecules and how these atoms form chemical bonds to create compounds, it is important for chemists to determine the amount of a substance on the molecular scale. Although the common use of the term “amount of substance” used in Engineering may be interpreted as the weight (in grams) or the volume (in cm 3) of a substance, in chemistry the amount of a substance is a measure of the number of fundamental particles, such as atoms, molecules, or ions that are present in a given mass of substance. The SI base unit for the amount of a substance is the mole...
eBook - ePubMWH's Water Treatment
Principles and Design
- John C. Crittenden, R. Rhodes Trussell, David W. Hand, Kerry J. Howe, George Tchobanoglous(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
...Selectivity is equal to the moles of desired product divided by the moles of reactant that has reacted. Series reactions Individual reactions that proceed sequentially to generate products from reactants. Stoichiometry A quantitative relationship that defines the relative amount of each reactant consumed and each product generated during a chemical reaction. Chemical reactions are used in water treatment to change the physical, chemical, and biological nature of water to accomplish water quality objectives. An understanding of chemical reaction pathways and stoichiometry is needed to develop mathematical expressions that can be used to describe the rate at which reactions proceed. Kinetic rate laws and reaction stoichiometry are valid regardless of the type of reactor under consideration and are used in the development of mass balances (see Chap. 6) to describe the spatial and temporal variation of reactants and products in chemical reactors. Understanding the equilibrium, kinetic, and mass transfer behavior of each unit process is necessary in developing effective treatment strategies. Equilibrium and kinetics are both introduced in this chapter, and mass transfer is discussed in Chap. 7. Topics presented in this chapter include (1) chemical reactions and stoichiometry, (2) equilibrium reactions, (3) thermodynamics of chemical reactions, (4) reaction kinetics, (5) determination of reaction rate laws, and (6) chemical reactions used in water treatment. Water chemistry textbooks (Benefield et al., 1982; Benjamin, 2002; Pankow, 1991; Sawyer et al., 2003; Snoeyink and Jenkins, 1980; Stumm and Morgan, 1996) may be reviewed for more complete treatment of these concepts and other principles of water chemistry. 5.1 Chemical Reactions and Stoichiometry Chemical operations used for water treatment are often described using chemical equations...
- Kevin Reel, Derrick C. Wood, Scott A. Best(Authors)
- 2014(Publication Date)
- Research & Education Association(Publisher)
...Chapter 3 Stoichiometry and Chemical Equations Chemical Equations • Chemical equations are prescribed recipes that chemists use to represent the ingredients and the end product(s) for chemical reactions. • Equations also indicate the amounts and states of matter of the species involved in a reaction. • It is always necessary to balance chemical equations; otherwise, the reaction would violate the law of conservation of mass. • Equations are balanced by adding coefficients in front of the atoms or compounds. You may only change the number of each species that you have on the reactant or products side of an equation. Never change the formula of the compound! In order to efficiently balance equations: 1. Write out the correct formulas for the reactants and products. 2. Balance atoms other than oxygen and hydrogen first. 3. Try to balance polyatomic ions as a unit. 4. Balance oxygen and hydrogen after most of the other atoms are balanced. 5. If there are any single atoms or diatomic molecules like O in the equation, save them for last. 6. Avoid fractions as coefficients! 7. Redox reactions must be balanced for both atoms and charge. See the next section on “Balancing Redox Reactions.” EXAMPLE: Aqueous solutions of ammonium phosphate and calcium chloride react to form solid calcium phosphate and a solution of ammonium chloride. SOLUTION: See the following steps for the explanation; changes for each step are underlined and in bold. Step 1: (NH 4) 3 PO 4(aq) + CaCl 2(q) → Ca 3 (PO 4) + NH 4 Cl (aq) Step 2: (NH 4) 3 PO 4(aq) + 3 CaCl 2(q) → Ca 3 (PO 4) 2(s) + NHCl 4 Cl (aq) Step 3: 2 (NH 4) 3 PO 4(aq) + 3 CaCl 2(aq) → Ca 3 (PO 4) 2(s) + 6 NH 4 Cl (aq) Double-check to make sure everything is. balanced, such as the chlorine atoms. Otherwise, this equation is balanced. TEST TIP If you are having trouble balancing an equation, check to make sure that the formulas are correct...
