Students in chemistry labs are often asked to calculate the actual yields of their reactions to determine reaction efficiency. The efficiency of a reaction dictates its use and practicality; an efficient reaction will be used more frequently in an industrial setting, and therefore has much more value. Every chemical reaction has two yields: the theoretical yield and an actual yield. The theoretical yield is the yield for a 100 percent efficient reaction. The actual yield is calculated with respect to the theoretical yield to determine reaction efficiency.
Calculate the theoretical yield for your particular chemical reaction. The calculations for the theoretical yield are significantly more complicated than those for the actual yield, and your professor will probably walk you through this step.
Perform your laboratory reaction, making sure that you do not “lose” any product along the way. Since no reaction is 100 percent efficient, you will always end up with less reaction product than you expect. However, you should take care to clean out all your beakers and lab equipment to make sure that you do not leave some product behind at any stage, since this will throw off your calculations.
Weigh your final product once you complete the lab process. If your product is wet at the final stage, which is quite common, let the water evaporate out before you weigh it. Otherwise, you will include the weight of the water in the weight of your final product, which will inflate the efficiency of your reaction.
Divide the weight of your reaction products that you got in Step 3 by the theoretical yield that you got in Step 1. Make sure that both of your yields are in grams.
Multiply the answer that you got in Step 4 by 100 to get your final actual yield. This actual yield is expressed as a percentage of the theoretical yield; if your actual yield is 76, then this means that you recovered 76 percent of the product that you would have gotten if your reaction were 100 percent efficient.
Things You'll Need
Required lab equipment