Regarding the definition of yield, I seek answers from experts
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A factory produces 300 tons per year of p-nitroethylbenzene with a purity of 99%. The yield of mononitroethylbenzene is 50%, and the purity of the starting material ethylbenzene is 95%. If there are 300 working days per year, what is the mass of ethylbenzene required per hour, in kilograms, to the nearest value? The answer to this question is 86.8 kg, but I got 60 kg every time I calculated it; there might be some issue with a detail somewhere. Please advise me if you know what it is. I wrote down my solution process: The molecular weight of p-nitroethylbenzene is 151 ； The molecular weight of ethylbenzene is 106. The actual mass of mononitroethylbenzene produced per hour by this factory is: 300*1000*99%÷300÷24 = 41.25 kg/h. If the mass of ethylbenzene required per hour is A kg, then the theoretical amount of mononitroethylbenzene that can be produced from A kg of this raw material is: A*95%*151÷106. With a yield of 50% for mononitroethylbenzene, we have: 41.25÷(A*95%*151÷106) = 50%. Solving for A gives A = 60.96 kg/h. I hope someone experienced in this field can help identify the mistake. Thank you! http://image.keyan.cc/data/emuch_bbs_images/smilies/hand.gif I thought it over later, and the correct answer of 86.8 kg/h might be derived in this way: 41.25 ÷ 50% = 82.5 kg, and then 82.5 ÷ 95% = 86.8 kg. So here comes the question: I searched Baidu for the definition of yield. Yield (or percent yield), also known as reaction yield, is commonly used in chemistry and industrial production. It refers to the ratio of the actual amount of product obtained from a given amount of raw material in a chemical reaction or related industrial process, to the theoretical amount of product that could be produced. Yield = (Amount of product formed / Amount of reactant fed) × 100%. If I calculate using the definition above, it will be incorrect ； If calculated using the definition below, it will be correct. It’s still a matter of definition. I also saw a definition of yield in a reference book: Yield = Amount of the key component consumed to produce the desired product ÷ Initial amount of that key component. These three definitions of yield are completely different; it’s really frustrating. http://image.keyan.cc/data/emuch_bbs_images/smilies/rolleyes.gif If calculated correctly, the second definition I provided is the right one; from the perspective of this problem, the yield of mononitroethylbenzene equals the actual mass of mononitroethylbenzene produced divided by the mass of ethylbenzene used as the raw material, assuming that both mononitroethylbenzene and ethylbenzene have a purity of 100%. However, according to the definitions in many reference books, the third definition is the correct one. So I’m really stuck now; could an expert give some guidance?
As defined in \"Chemical Reaction Engineering (5th Edition)\) edited by Zhu Bingchen: Yield = amount (mol) of the key component consumed to produce the desired product / amount (mol) of the key component that enters the reaction system. Using this definition, the calculated value is also 60.96 kg/h; could there be an issue with the given answer?
I think the original poster is correct; the yield is calculated on a molar basis.
Different industries vary; all of these calculation methods are correct. If it is a physical separation, then use this method: the ratio of the actual output produced to the theoretically calculated output. This is the algorithm for cumulative amounts; when it comes to chemical reactions, the target product is used, and the yield is calculated as the amount of the key component consumed to produce the target product divided by the initial amount of that key component. This is the algorithm for process amounts, or alternatively, the yield can be expressed as (amount of target product produced / amount of reactant fed in) × 100%. This last formula is the most commonly used, but it’s not necessarily correct
Definition 1: Yield (or percent yield), also known as reaction yield, is commonly used in chemistry and industrial production. It refers to the ratio of the actual amount of product obtained from a given quantity of reactants in a chemical reaction or related industrial process, to the theoretical amount of product that could be produced. Definition 2: Yield = (Amount of target product produced / Amount of reactant fed in) × 100%. Definition 3: Yield = Amount of the key component consumed to produce the target product ÷ Initial amount of that key component. Definitions 1 and 3 are essentially the same; they just are expressed differently ； Definition two is incorrect or custom-defined, and is not advisable. The original poster calculated it according to Definition 1; below is my calculation based on Definition 3, and the result is the same. (41.25/151) / (0.95A/106) = 0.5 A = 60.96
After looking at the three definitions above, I would just like to say that the first definition refers not to yield, but to productivity. It represents the ratio of actual yield to theoretical yield. According to the second definition, if it is a ratio of masses, then it is called the mass yield. It represents the ratio of the required product to the quality of the input materials. If it is a molar ratio, there is no specialized term. The third definition is the yield definition.
This post was last edited by Higee on 2015-9-14 09:40. In physical separation, the yield is defined as the ratio of the actual amount of product obtained to the theoretical amount that could be obtained. In chemical reactions, yield refers to the ratio of the amount of reactant consumed to produce the target product to the amount of that reactant used in the reaction. There is no such concept as yield in physical separation processes, as no new substances are formed. In chemical reactions, yield can be used, but it seems to be the same as productivity, at least for single reactions
Personally, I think the original poster’s answer is correct
The answer is very good. Definition 2: Yield = (Amount of target product produced / Amount of reactants used) × 100%. This is how it is defined in industrial production. Definition 3: Yield = Amount of the key component consumed to produce the target product ÷ Initial amount of that key component. This is the definition given in exam textbooks; it’s a theoretical definition. Definition 2 and Definition 3 can be converted into one another through the reaction stoichiometric coefficients, which are obtained from the overall reaction equation for the process.
95%X/106*50%*151*300*24=300*1000*99%