Stoichiometric calculations theoretical yield

The amounts of products calculated in the stoichiometric problems so far represent theoretical yields. The theoretical yield is the maximum amount of product that can be produced from a given amount of reactant. In most chemical reactions, the amount of product obtained from a reaction is less than the theoretical yield. The measured amount of a product that is obtained from a reaction is called the actual yield of that product. 

The calculation shows that the stoichiometric yield RY is acceptable, but the theoretical balance yield BAt poor, because catalyst complex lost after reaction. A significant improvement would be the use of solid catalyst. Other alternative is regeneration of A1C13 complex by recycling. The two solutions would lead to the same theoretical yield, but with different costs. Therefore, a deeper investigation should take into account a cost flow analysis too. More details can be found in Christ [2]. 

The amount of Pbl2 calculated in part a, 192.71 g, is known as the theoretical yield of the substance. That is the maximum amount that can form based on the stoichiometric relationships between reactants and products. The actual reaction will more than likely produce less than this, for a variety of reasons (which are unimportant to us). 

The percentage yield of a chemical reaction compares the mass of product obtained by experiment (the actual yield) with the mass of product determined by stoichiometric calculations (the theoretical yield). It is calculated as follows ... 

When 7.5 x 101 g of nitrogen reacts with sufficient hydrogen, the theoretical yield of ammonia is 9.10 g. (You can verify this by doing the stoichiometric calculations.) If 1.72 g of ammonia is obtained by experiment, what is the percentage yield of the reaction ... 

Although equations tell you what should happen in a reaction, they cannot always tell you what will happen. For example, sometimes reactions do not make all of the product predicted by stoichiometric calculations, or the theoretical yield. In most cases, the actual yield, the mass of product actually formed, is less than expected. Imagine that a worker at the flavoring factory mixes 500.0 g isopentyl alcohol with 1.25 x 10 g acetic acid. The actual and theoretical yields are summarized in Table i. Notice that the actual yield is less than the mass that was expected. 

The yield of a reaction is the amount of product obtained. This value is nearly always less than what would be predicted from a stoichiometric calculation because side-reactions may produce different products, the reverse reaction may occur, and some material may be lost during the procedure. The yield from a stoichiometric calculation on the limiting reagent is called the theoretical yield. Percent yield is the actual yield divided by the theoretical yield times 100% ... 

Stoichiometry is the quantitative study of products and reactants in chemical reactions. Stoichiometric calculations are best done by expressing both the known and unknown quantities in terms of moles and then converting to other units if necessary. A limiting reagent is the reactant that is present in the smallest stoichiometric amount. It limits the amount of product that can be formed. The amount of product obtained in a reaction (the actual yield) may be less than the maximum possible amount (the theoretical yield). The ratio of the two is expressed as the percent yield. 

Before going to lab, a student read in her lab manual that the percent yield for a difficult reaction to be studied was likely to be only 40.% of the theoretical yield. The student s prelab stoichiometric calculations predict that the theoretical yield should be 12.5 g. What is... 

The reaction mixture contains fixed amoimts of NH3 and CO2, and so we must first determine which reactant is the limiting reactant. The stoichiometric proportions are 2 mol NH3 1 mol CO2. In the reaction mixture, the mole ratio of NH3 to CO2 is 3 1. Therefore, NH3 is the excess reactant and CO2 is the limiting reactant. The calculation of the theoretical yield of urea must be based on the amount of CO2, the limiting reactant. Because the quantity of urea is given per mole of CO2, we should base the calculation on 1.00 mol CO2. The following conversions are required mol CO2 mol CO(NH2)2 g CO(NH2)2-... 

Other Practical Matters in Reaction Stoichiometry— Stoichiometric calculations sometimes involve additional factors, including the reaction s actual yield, the presence of by-products, and how the reaction or reactions proceed. For example, some reactions yield exactly the quantity of product calculated—the theoretical yield. When the actual yield equals the theoretical yield, the percent yield is 100%. In some reactions, the actual yield is less than the theoretical, in which case the percent yield is less than 100%. Lower yields may result from the formation of by-products, substances that replace some of the desired product because of reactions other than the one of interest, called side reactions. Some stoi-... 

The problem asks for a yield, so we identify this as a yield problem. In addition, we recognize this as a limiting reactant situation because we are given the masses of both starting materials. First, identify the limiting reactant by working with moles and stoichiometric coefficients then carry out standard stoichiometry calculations to determine the theoretical amount that could form. A table of amounts helps organize these calculations. Calculate the percent yield from the theoretical amount and the actual amount formed. 

The atom utilization or atom efficiency concept is a useful tool for rapid evaluation of the amount of waste that will be generated by alternative routes to a particular product. It is calculated by dividing the molecular weight of the desired product by the sum total of the molecular weights of all the substances produced in the stoichiometric equation of the reaction(s) in question. The comparison is made on a theoretical (i.e. 100% chemical yield) basis. Fig. 2.8 shows a simple illu.stration of the concept for ethylene oxide manufacture. 

Since the DGEBA/DDS networks are tetrafunctional and of stoichiometric composition, the theoretical value of z is 2. Furthermore, the crosslink concentration, c, is simply the DDS molecule concentration. Performing the necessary calculations yields the theoretical M, listed in Table 4. Compared to the experimental M, the theoretical values are very consistent. If it is assumed that the DGEBA/DDS networks are not phantom-like (i.e., A = 1), then the ratio of the theoretical and experimental values may serve as an estimate of the dilation factor, These ratios are listed in Table 4, and show that is approximately unity for all the networks. If the experimental M had been calculated using the actual network densities (instead of q = 1 g/cm), the ratios would be even closer to unity, being reduced by approximately 20 percent. 

Once the stoichiometry of the complex has been established, the stability constant(s) can be calculated, provided the data yields a curve showing some dissociation in the neighborhood of the stoichiometric point (curve B in Figure 22-12). Briefly, for any data point in the region of curvature, complex formation did not proceed to completion, as evidenced from the difference between the measured curve and the "theoretical" one. Here there is obviously an equilibrium between metal ion, ligand and complex, and from each data point a value of the stability constant can be calculated. 

Stoichiometric yield can be calculated as the ratio between the actual product to the theoretical amount to be obtained from the reference reactant ... 

Theoretical balance yield BA, is a measure of an ideal process. In contrast with the stoichiometric yield, the theoretical balance yield is calculated as the ratio between the moles of the target product and the total moles of the primary raw materials (PRM), including all reactants involved in the stoichiometry of the synthesis route ... 

The cyanoacetic acid obtained from monochloroacetic acid and sodium cyanide, is treated with hydrochloric acid and ethanol to yield the diethyl ester of malonic acid. The ester, in absolute ethanol, is reacted with the stoichiometric proportion of metallic sodium so as to replace only one active hydrogen of the methylene (CH2) group. Thereupon, a slight excess of the calculated amount of allyl bromide is added. The second replaceable hydrogen is abstracted with 1-methyl butyl bormide and the resulting product is made to react with a theoretical amount of thiourea to yield thiamylal. The free acid thus obtained is conveniently transformed into the official sodium salt by neutralization with a stoichiometric proportion of sodium hydroxide (1 1). 

Stoichiometric Yield, material planing productivity is normally calculated in terms of the stoichiometric yield. This is based on the reaction equation, which describes the chemical process in question in the form of an ideal model. It allows the calculation of the theoretical amount of the target product given the amount of the main educt chosen. The stoichiometric yield of the target product is the ratio of the actual amount produces to the theoretical amount expected [55]. The stoichiometric yield is calculated on one educt and is thus dependent on the substance chosen as the main educt. The... 

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