Chemical reaction percent yield

From the equation representing the chemical reaction involved, it is evident that 330 g. of silver maleate will theoretically react with 312 g. of ethyl iodide in ethereal solution to produce 172 g. of ethyl maleate. It follows, therefore, that 33 g. (0 1 mol) of silver maleate will react with 31-2 g. (0-2 mol) of ethyl iodide to give a theoretical yield of 17 2 g. (0 1 mol) of ethyl maleate. In practice, the actual yield foimd for these quantities is of the order of 16-0 g. the percentage yield is therefore (16 0/17-2) X 100 = 93 percent. 

The percent yield is 100 times the amount of a product actually prepared during a reaction divided by the amount theoretically possible to be prepared according to the balanced chemical equation. (Some reactions are slow, and sometimes not enough time is allowed for their completion some reactions are accompanied by side reactions which consume a portion of the reactants some reactions never get to completion.) If 3.00g C6H,Br is prepared by treating 3.00g ChHl2 with excess Br2, what is the percent yield The equation is... 

In the problem above, the amount of product calculated based upon the limiting reactant concept is the maximum amount of product that will form from the specified amounts of reactants. This maximum amount of product is the theoretical yield. However, rarely is the amount that is actually formed (the actual yield) the same as the theoretical yield. Normally it is less. There are many reasons for this, but the principal one is that most reactions do not go to completion they establish an equilibrium system (see Chapter 14 for a discussion on chemical equilibrium). For whatever reason, not as much product as expected is formed. We can judge the efficiency of the reaction by calculating the percent yield. The percent yield (% yield) is the actual yield divided by the theoretical yield and the resultant multiplied by 100 in order to generate a percentage ... 

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. 

If we now plot the percent yield vs. the solvent number, we will get the response surface shown in Figure 2.11. There seems to be a trend toward higher yield with increasing solvent number, but such a trend must be meaningless it is difficult to imagine how an arbitrarily assigned number could possibly influence the yield of a chemical reaction. If a relationship does appear to exist between yield and solvent number, it must be entirely accidental - the variation in response is probably caused by some other property of the solvents. 

Many conditions are required for a chemical reaction to proceed. Conditions such as heat, light, and pressure must be just right for a reaction to take place. Furthermore, the reaction may proceed very slowly. Some reactions occur in a fraction of a second, while others occur very slowly. Consider the difference in the reaction times of gasoline igniting in a car s cylinder versus the oxidation of iron to form rust. The area of chemistry that deals with how fast reactions occur is known as kinetics (Chapter 12). Finally, not all reactions go to completion. The amount of product produced based on the chemical equation is known as the theoretical yield. The amount actually obtained expressed as a percent of the theoretical is the actual yield. In summary, it s best to think of a chemical equation as an ideal representation of a reaction. The equation provides a general picture of the reaction and enables us to do theoretical calculations, but in reality reactions deviate in many ways from that predicted by the equation. 

The actual yield will always be less than the theoretical yield because no chemical reaction ever reaches 100 percent completion. In a lab setting, there s always some cimount of error, whether it s big or small. 

Having covered the major components of a chemical reaction, with the exception of energy considerations, the last topic is doing an overall evaluation of a process. There are two straightforward parameters that may be calculated for a reaction that give some indication of efficiency. One is the percent yield of the purified product. The second is atom economy, which was developed by Barry Trost (1991) of Stanford University. Atom economy can be used to determine the fraction of the molecular weight of the reactant(s) incorporated into the product(s). Separate atom economies are calculated for each product of a reaction. 

A barrel of crude oil has limited value, if any, to consumers. Its true value is the number of value-added products that can be extracted from the crude oil using various chemical reactions and separation methods. Thus, the refining operation is the first step in the transformation of crude petroleum oil into consumer products. So what are the possible products from a barrel of crude oil Figure 18.6 lists the average breakdown of a barrel of oil by a United States refinery. As shown in Fig. 18.6, over 75 percent of the product yield from a refined barrel of oil is fuel based. In this example, United States refineries are focused on gasoline production, whereas European refineries focus on diesel product. Yet, refineries can also produce value-added petrochemicals for adjacent facilities. 

The gaseous air/S03 sulfonation process normally generates a product composed of 95-98 percent ABS, 1-2 percent sulfuric acid, and 1-2.5 percent unsulfonated oils. Although the initial capital costs are much higher than those for an oleum process, relative sulfonic acid yields and spent acid disposal costs are substantially lower. The chemical reactions involved in air/S03 sulfonation are shown in... 

You will determine the percent yield of a chemical reaction. 

The problem-solving LAB on page 372 will help you understand the importance of percent yield in chemical reactions and the kind of factors that may determine the size of the percent yield. 

When copper wire is placed into a silver nitrate solution, silver crystals and copper(ll) nitrate solution form. Write the balanced chemical equation for the reaction. If a 20.0-g sample of copper is used, determine the theoretical yield of silver. If 60.0 g silver is actually recovered from the reaction, determine the percent yield of the reaction. 

Zinc reacts with iodine in a synthesis reaction. Write the balanced chemical equation for the reaction. Determine the theoretical yield if a 125.0-g sample of zinc was used. Determine the percent yield if 515.6 g product is recovered. 

Can the percent yield of a chemical reaction be more than 100% Explain your answer. (12.4)... 

What experimental information do you need in order to calculate both the theoretical and percent yield of any chemical reaction (12.4)... 

Percent Yields from Chemical Reactions Reactions... 

SoUd silver nitrate undergoes thermal decomposition to form silver metal, nitrogen dioxide, and oxygen. Write the chemical equation for this reaction. A 0.443-g sample of silver metal is obtained from the decomposition of a 0.784-g sample of AgN03. What is the percent yield of the reaction ... 

The maximum quantity of product that can be obtained from a chemical reaction is the theoretical yield. Invariably some waste occurs during the isolation and purification of products, however no matter how good a chemist you are, you will invariably lose small quantities of material along the way. For this reason, the actual yield of a compound—the quantity of material you actually obtain in the laboratory or chemical plant— is likely to be less than the theoretical yield. The efficiency of a chemical reaction and the techniques used to obtain the desired compound in pure form can be evaluated by calculating the ratio of the actual yield to the theoretical yield. We call the result the percent yield (Figure 4.10). 

It was soon realized that the error introduced by the Hartree-Fock model, which is the so-called correlation energy A = E i — E , is small for closed-shell systems (of the order of a few percent) but decisive for chemical reaction energetics. Moreover, weak interactions of the van der Waals type cannot be described with such a single-determinant Hartree-Fock model. Consequently, Hartree-Fock calculations on supramolecular assemblies, whose interaction is governed by weak dispersion forces, cannot provide accurate quantitative results and are likely to yield a wrong qualitative picture. However, in certain cases Hartree-Fock results may be of value. For instance, Houk and coworker have investigated the role of [C-H O] interactions in supramolecular complexes by means of dynamic and static Hartree-Fock calculations [59]. 

Given an actual yield and a theoretical yield (or enough information to calculate a theoretical yield) for a chemical reaction, calculate the percent yield for the reaaion. 

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