Chemical equations calculating reacting quantities

The coefficients in a balanced equation give the ratio of moles of each substance in the reaction to moles of any other substance. They also give the ratio of formula units of each substance to formula units of any other substance. The balanced chemical equation is the cornerstone from which we can calculate how much of one substance reacts with or is produced by a certain quantity of another substance (Chapter 10). 

Calculations that involve chemical reactions use the proportions from balanced chemical equations to find the quantity of each reactant and product involved. As you learn how to do these calculations in this section, you will assume that each reaction goes to completion. In other words, all of the given reactant changes into product. For each problem in this section, assume that there is more than enough of all other reactants to completely react with the reactant given. Also assume that every reaction happens perfectly, so that no product is lost during collection. As you will learn in the next section, this usually is not the case. 

A chemical equation provides a variety of qualitative and quantitative information essential for the calculation of the quantity of reactants reacted and products formed in a chemical process. The balanced chemical equation must have the same number of atoms of each type in the reactants and products. Thus the balanced equation for butane is... 

Since 2.0 mol HCl is required to react with all the NaOH and there is 3.0 mol of HCl present, HCl present in excess. If HCl is in excess, NaOH must be limiting. It is not necessary to do both calculations. The same result will be obtained no matter which is used. If the quantities of both reactants are in exactly the correct ratio for the balanced chemical equation, then either reactant maybe used to calculate the quantity of product produced. 

In a chemical reaction, there is a definite ratio between the number of moles of a particular reactant or product and the number of moles of any other reactant or product. These ratios are readily seen by simply examining the coefficients in front of the reaction species in the chemical equation. Normally, a stoichiometric calculation is performed to relate the quantities of only two of the reaction participants. The objective may be to determine how much of one reactant will react with a given quantity of another reactant Or, a particular quantity of a product may be desired, so that it is necessary to calculate the quantity of a specific reactant needed to give the amount of product To perform stoichiometric calculations involving only two reaction participants, it is necessary only to know the relative number of moles of each and their molar masses. The most straightforward type of stoichiometric calculation is the mole ratio metiiod defined as follows ... 

The numerical relationship between chemical quantities in a balanced chemical equation is called reachon stoichiometry. Stoichiometry allows us to predict the amounts of products that form in a chemical reaction based on the amounts of reactants. Stoichiometry also allows us to predict how much of the reactants are necessary to form a given amoxmt of product, or how much of one reactant is required to completely react with another reactant. These calculations are central to chemistry, allowing chemists to plan and carry out chemical reactions to obtain products in the desired quantities. 

In Chapter 2, we described a chemical equation as a representation of what occurs when molecules react. We will now study chemical equations more closely to answer questions about the stoichiometry of reactions. Stoichiometry (pronounced stoy-key-om -e-tree ) is the calculation of the quantities of reactants and products involved in a chemical reaction. It is based on the chemical equation and on the relationship between mass and moles. Such calculations are fundamental to most quantitative work in chemistry. In the next sections, we will use the industrial Haber process for the production of ammonia to illustrate stoichiometric calculations. 

How can the observable and measurable quantities of matter expressed in chemical equations be calculated The balancing coefficients play the central role. Let us look at a simple example to illustrate the point, comparing the moles of oxygen that will react with a given number of moles of hydrogen. 

The integration constant of this equation left undetermined by thermodynamics is therefore the sum of the vapour pressure constants of the individual reacting substances. In this way it is possible in principle to calculate chemical equilibria at all temperatures from thermal quantities (calorimetric measurements) and vapour pressure measurements with the individual reacting substances. 

From the quantities above, it can be seen that the equation can be viewed in terms as small as the smallest number of molecules and formula units. In this case, that involves simply 1 formula unit of CaCOg (s), 1 formula unit of CaO is), and 1 molecule of CO2. This would involve a total of 1 Ca atom, 1 C atom, and 3 O atoms. From such a small scale, it is possible to expand to moles by scaling up by 6.022 X 10 (Avogadro s number), giving 100.1 g of CaCOg, 56.Ig of CaO, and 44.0 g of CO2. Actually, these quantitative relationships are applicable to any amount of matter, and they enable the calculation of the amounts of material reacting and produced in a chemical reaction. Next, it is shown how these kinds of calculations are performed. 

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