Formulas, Chemical Equations, and Reaction Yields

Chemical Formulas, Chemical Equations, and Reaction Yields 

An assay balance of careful construction of the type used by Lavoisier before 1788. This balance became the production model that served as a general, all-purpose balance for approximately 40 years. Users of this type of balance Included Sir Humphrey Davy and his young assistant Michael Faraday. 

I hapter 1 explained how chemical and physical methods are used to estab-lish chemical formulas and relative atomic and molecular masses. This chapter begins our study of chemical reactions. We start by developing the concept of the mole, which allows us to count molecules by weighing macroscopic quantities of matter. We examine the balanced chemical equations that summarize these reactions and show how to relate the masses of substances consumed to the masses of substances produced. This is an immensely practical and important subject. The questions how much of a substance will react with a given amount of another substance and how much product will be generated are central to all chemical processes, whether industrial, geological, or biological. 

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CHAPTER 2 Chemical Formulas, Chemical Equations, and Reaction Yields 31... 

If we know the chemical equation and the amounts of reactants, we can calculate the theoretical yield of that reaction. But in reality, the yield depends on many other factors also. Most of the time in synthesis reactions, even in your own lab experiments, you probably noticed that the actual yield is lower than the theoretical yield. The percent yield denotes the amount of actual yield in terms of the theoretical yield. The formula to find the percent yield is given below ... 

P, with the remainder oxygen. The mass spectrum of compound B yields a molar mass of 97.99 g-mol. Write the molecular formula of compound B. (c) Compound B reacts with an aqueous solution of calcium hydroxide to form compound C, a white precipitate. Write balanced chemical equations for the reactions in parts (a), (b), and (c). 

In this chapter, you learned how to balance simple chemical equations by inspection. Then you examined the mass/mole/particle relationships. A mole has 6.022 x 1023 particles (Avogadro s number) and the mass of a substance expressed in grams. We can interpret the coefficients in the balanced chemical equation as a mole relationship as well as a particle one. Using these relationships, we can determine how much reactant is needed and how much product can be formed—the stoichiometry of the reaction. The limiting reactant is the one that is consumed completely it determines the amount of product formed. The percent yield gives an indication of the efficiency of the reaction. Mass data allows us to determine the percentage of each element in a compound and the empirical and molecular formulas. 

A typical word statement of a chemical reaction is, Ammonia reacts with sulfuric acid to yield anunonium sulfate. The compounds or the ions involved in them have been given earlier in this book. Using correct chemical formulas, show the unbalanced and balanced chemical equations for this reaction. 

Sulfur combines directly with three of the halogens, but not with iodine. The products, however, do not have similar chemical formulas. When sulfur reacts with fluorine, sulfur hexafluoride is the most common product with chlorine, the product is usually sulfur dichloride and reaction with bromine usually yields disulfur dibromide. Write the equation for each reaction. 

Five tasks must be performed in this problem (1) Represent the reaction by a chemical equation in which the names of reactants and products are replaced with formulas. (2) Balance the formula equation by inspection. (3) Determine the limiting reactant. (4) Calculate the theoretical yield of sodium nitrite based on the quantity of limiting reactant. (5) Use... 

Explain the important distinctions between (a) chemical formula and chemical equation (b) stoichiometric coefficient and stoichiometric factor (c) solute and solvent (d) actual yield and percent yield (e) consecutive and simultaneous reactions. 

Write the unbalanced equation using the correct chemical formula for each reactant and product. In the reaction of hydrogen with oxygen to yield water, for example, we begin by writing ... 

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