Percentage yield determination

The percentage yield determined by the limiting reagent is the theoretical yield other losses may occur, resulting in a lower actual yield. 

Weigh the dry benzil and calculate the percentage yield. Determine the melting point. The melting point of pure benzil is 95°C. Submit the benzil to the instructor unless it is to be used to prepare benzilic acid (Experiment 32C). Obtain the infrared spectrum of benzil using the dry film method. Compare the spectrum to the one shown. Also compare the spectrum with that of benzoin. What differences do you notice ... 

Collect the crystals by vacuum filtration on a Hirsch fuimel. Use two 0.5-mL portions of ice-cold 95% ethanol to aid in the transfer. Allow the crystals to dry overnight or dry them for 30 minutes in a 75-80°C oven. Weigh the dry 6-ethoxy-carbonyl-3,5-diphenyl-2-cyclohexenone and calculate the percentage yield. Determine the melting point of the product (literature value, 111-112 C). Submit the sample to the instructor in a labeled vial. 

Weigh the purified trans,trans product and calculate the percentage yield. Determine the melting point of the product (literature, 151°C). 

When the distillation is complete, transfer the distillate to a tared 3-mL conical vial with a Pasteur pipette and weigh it to determine the percentage yield. Determine a microscale boiling point (Technique 13, Section 13.2) for your product. 

Analysis Weigh the recrystallized product and calculate the percentage yield determine the melting point. Obtain IR and NMR spectra of your starting materials and product, and compare them with those of authentic samples (Figs. 20.1-20.6). 

The 5-nitrofurfurylidene hydrazide of 4-hydroxybenzoic acid obtained was washed with water and methanol end was dried at a moderate temperature. It weighed 23 g (83.7% yield), and melted at 298°C. The percentage nitrogen determined by the micro-Dumas method was 15.41% (theory 15.27%). 

STRATEGY First, the limiting reactant must be identified (Toolbox M.l). This limiting reactant determines the theoretical yield of the reaction, and so we use it to calculate the theoretical amount of product by Method 2 in Toolbox L.l. The percentage yield is the ratio of the mass produced to the theoretical mass times 100. Molar masses are j calculated using the information in the periodic table inside the front cover of this i book. 

Table 3.18 gives the ratio of formation (where determined) of the cis and trans isomers and the percentage yields for various possible Ri, R2, R3, and R4. 

Another method for determining the efficiency of a chemical reaction is atom economy. Atom economy is a method of determining the efficiency with which raw materials (reactants or feedstocks) are used regardless of the percentage yield obtained in the reaction. 

Yield of Product. Where possible the methods employed in these preparations resemble those actually used on an industrial scale where this is impossible on the limited scale of the laboratory, mention is made of the fact, with reasons therefor. On account of the limitations connected with work on a laboratory scale, it is of course impossible to get as high percentage yields as could be obtained on a commercial scale. The weight of each preparation is to be determined and recorded, but the chief stress is to be... 

When the hydrochloric acid has cooled to room temperature determine the volume and the specific gravity of the solution in both absorption bottles. Use either a hydrometer or the apparatus shown in Fig. 19. Consult the table on page 371 and determine the percentage composition of the preparation. Calculate the weight of hydrogen chloride obtained, the normality of the solution, and the percentage yield. 

PCDD/F formation in combustors is a side-reaction which, in terms of percentage yield, is inconsequential relative to the dominant oxidative reactions between organic matter and chlorine in MSW and oxygen in combustion air. Literature sources indicate that the quantity of HC1 in process gases is at best a secondary determinant in influencing PCDD/F yields, and is much less important than the temperature-time window.27,28... 

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 ... 

How would you determine the percentage yield of a double displacement reaction that produces a precipitate Consider this question to prepare for your Chemistry Course Challenge. 

The percentage yield of a reaction is determined by numerous factors The nature of the reaction itself, the conditions under which the reaction was carried out, and the nature of the reactants used. 

In this investigation, you will determine the percentage yield of the following chemical reaction ... 

The 3rields of aldonic and oxalic acids are shown in Table XI. They are based on the amount of sugar oxidized (determined by reducing value) and not on the total amount of starting material. The formation of L-arabonic acid occurs with the highest percentage yield, but even this is low compared with other methods of preparation. As the lactobionic acid was isolated as the calcium lactobionate-calcium bromide salt, the actual amount of product, expressed in millimoles, is very low. 

When working in the laboratory, record everything you do and everything you observe as it happens. The recorded observations constitute the most important part of the laboratory record, as they form the basis for the conclusions you will draw at the end of each experiment. Record the physical properties of the product, the yield in grams, and the percentage yield. Analyze your results. When things do not turn out as expected, explain why. When your record of an experiment is complete, another chemist should be able to understand your account and determine what you did, how you did it, and what conclusions you reached. In other words, from the information in your notebook a chemist should be able to repeat your work. 

Determine the limiting reactant and the percentage yield for each of the following. 

Although the actual yield can only be determined experimentally, a close estimate can be calculated if the percentage yield for a reaction is known. The percentage yield in a particular reaction is usually fairly consistent. For example, suppose an industrial chemist determined the percentage yield for six tries at making banana flavoring and found the results were 80.0%, 82.1%,79.5%, 78.8%, 80.5%, and 81.9%. In the future, the chemist can expect a yield of around 80.5%, or the average of these results. 

Determine the percentage yield of a reaction from its calculated theoretical yield and its measured actual yield (Section 2.6, Problems 49 and 50). 

---