Given by Chemical Equations

As we saw in the last two chapters, chemistry is really about reactions. Chemical changes involve rearrangements of atom groupings as one or more substances change to new substances. Recall that reactions are described by equations that give the identities of the reactants and products and show how much of each reacfanf and producf parficipafes in fhe reaction. If is the numbers (coefficients) in the balanced chemical equation that enable us to determine just how much product we can get from a given quantity of reacfanfs. 

To explore fhis idea, consider a nonchemical analogy. Assume fhat you are in charge of making deli sandwiches af a local fasf-food resfaurant. A particular type of sandwich requires 2 pieces of bread, 3 slices of meat, and 1 slice of cheese. You mighf represenf making fhis sandwich by the following equation  

2 pieces bread + 3 slices meaf + 1 slice cheese 1 sandwich 

Your boss sends you to the store to get enough ingredients to make 50 sandwiches. How do you figure out how much of each ingredient to buy Because you need enough to make 50 sandwiches, you could multiply the preceding equation by 50. 

50 (2 pieces bread) + 50 (3 slices meat) + 50 (1 slice cheese) 

---

Information Given by Chemical Equations Mole-Mole Relationships Mass Calculations The Concept of Limiting Reactants... 

When liqiiid-phase chemical reactions are extremely slow, the gas-phase resistance can be neglected and one can assume that the rate of reaction has a predominant effect upon the rate of absorption. In this case the differential rate of transfer is given by the equation... 

Chemical reactions are represented by chemical equations, which identify reactants and products. Formulas of reactants appear on the left side of the equation those of products are written on the right In a balanced chemical equation, there are the same number of atoms of a given element on both sides. The same situation holds for a chemical reaction that you carry out in the laboratory atoms are conserved. For that reason, any calculation involving a reaction must be based on the balanced equation for that reaction. 

Most of the remainder of this chapter is devoted to a discussion of the magnitude of the heat flow in chemical reactions or phase changes. However, we will focus on a simpler process in which the only effect of the heat flow is to change the temperature of a system. In general, the relationship between the magnitude of the heat flow, q, and the temperature change, At, is given by the equation... 

Replacement of a hydrogen atom within an organic molecule, for example an alkane, by a substituent X changes the electronic environments of directly bonded and of more remote carbon nuclei. Thereby l3C NMR signals are shifted either upheld or downfield the difference between the chemical shifts 8 of a certain carbon atom in the substituted and the unsubstituted parent compound is called the substituent effect. For this term the abbreviation SCS (substituent-induced chemical shift) has generally been adopted in the literature and will also be used here. The SCS is given by the equation... 

Bioconcentration Factor in Aquatic Organisms. The bioconcentration factor (BCE) indicates the degree to which a chemical may accumulate in aquatic organisms, such as fish, clams, and zooplankton. It is given by the equation... 

Chemical composition analysis complementing the microstructural information obtained from EM is known as analytical EM (AEM). Important compositional variations or non-stoichiometry in a material which is seemingly phase pure or stoichiometric by the criterion of bulk diffraction techniques and compositions of surface layers can be revealed using AEM. For quantitative microanalysis a ratio method for thin crystals (Cliff and Lorimer 1975) is used, given by the equation ... 

Equilibrium constants are normally given for chemical equations written with the smallest whole numbers for the stoichiometric coefficients. However if we change the stoichiometric coefficients in a chemical equation (for instance, by multiplying through by a factor), then we must make sure that the equilibrium constant reflects that change. For example, at 700 K,... 

Inserting Eq. (82) into Eq. (81) gives the qualifying Eq. (83) to predict the locus curve X],uz = l ),ky(xi,az) at which possible reactive arheotropes can be found (i.e., the potential singular point surface, PSPS). The second curve is given by the equation describing the chemical equilibrium x>az = Fchem(xi az)-... 

A chemical reaction may be carried out at other temperatures rather than 25°C for the enthalpy change. The effect of temperature on AH at constant pressure can be given by differentiating Equation (1.35) with respect to temperature as ... 

In order to aid the quick understanding of the reader, most synthetic methods are shown by chemical equations, and the yields and reaction conditions are also given in as much detail as possible. 

For a chemical reaction the enthalpy change is given by the equation... 

---