USING ENGLISH TO PREDICT RENDEMENT OF PRODUCT A REACTION

               

Rendemen chemical

In chemistry, the chemical yield, the yield of the reaction, or only the rendement refers to the amount of reaction product produced in the chemical reaction. Absolute rendement can be written as weight in grams or in moles (molar yield). The relative yield used as a calculation of the effectiveness of the procedure is calculated by dividing the amount of product obtained in moles by the theoretical yield in moles:

Fractional yield =       true rendement                                             theoretical rendement

To obtain a percentage yield, multiply the fractional yield by 100%. One or more reactants in chemical reactions are often used redundantly. The theoretical rendement is calculated based on the number of moles of the limiting reaction. For this calculation, it is usually assumed there is only one reaction involved.

The ideal chemical yield value (theoretical rendement) is 100%, a value highly unlikely to be achieved in its practice. Calculate the percentage of rendement that is by using the following equation percent rendemen = weight yield / weight of yield divided by the sample weight multiplied 100%.

1.  Balancing The Chemical Equation: The first step in finding theoretical and percentage yield is to balance the relevant chemical equation. If you are unsure how to do this, click on the "How to Balance Chemical Equations" link below:  2.  Finding The Limiting Reagent:  this is the reactant which the product yield depends on, as it is not in excess. To determine which reactant is the limiting reagent               1(a).   Divide the mass (in grams) of the reactant by its molecular weight (in g/mol)  OR               1(b).   Multiply the amount used (in mL) by its density, then divide by its molar mass              2.  Multiply the mass (your answer from steps 1(a) or 1(b)) by the number of moles of the reactant used in the reaction. Unsure of how to calculate molar mass or molecular weight? Click the link below:

3.  Theoretical Yield this is how much product will be synthesized in ideal conditions. To determine theoretical yield, multiply the amount of moles of the limiting reagent by the ratio of the limiting reagent and the synthesized product and by the molecular weight of the product. 4.  Actual Yield this is how much product was actually synthesized in the experiment. Example:  0.135 g acetylsalicylic acid

5.  Percent Yield The percentage yield is the ratio between the actual yield and the theoretical yield multiplied by 100%.  It indicates the percent of theoretical yield that was obtained from the final product in an experiment.  The percentage yield can be calculated using the mass of the actual product obtained and the theoretical mass of the product calculated using the balanced equation of the reaction. molar mass of p-aminophenol =109.1g/mol molar mass of acetic anhydride = 102.1 g/mol moles of p-aminophenol = mass/molar mass                                   = 0.157g/(109.1g/mol)                                   = 0.00144 mol moles of acetic anhydride = mass/molar mass                                          = 0.486g/(102.1g/mol)                                          = 0.00476 mol From the balanced chemical equation we know that for every mole of p-aminophenol and acetic acid one mole of acetaminophen is produced. Since there are more moles of acetic anhydride than p-aminophenol, p-aminophenol is used up first as the reaction proceeds.  We can conclude that acetic anhydride is in excess and p-aminophenol is the limiting reagent. Therefore # moles of p-aminophenol = # of acetaminophen produced Finding the Theoretical Yield Theoretical Yield = moles of acetamiophen x molar mass of acetaminophen                          = 0.00144 mol x 151.2g/mol                          = 0.217 g Finding the Percent Yield Percent Yield =         Actual Yield        x 100%                             Theoretical Yield                     =            0.198g      x 100 %                                   0.217g                     =  91.2 %