This video explains how to calculate the limiting reagent and percent yield of a chemical reaction. We will be looking at the reaction between hematite and carbon. We can see from our balanced chemical reaction equation that two molecules of hematite react with three molecules of carbon to produce four molecules of solid iron and three molecules of carbon dioxide gas. The problem we are asked to solve is what is the limiting reagent when 550 grams of hematite react with 100 grams of carbon? What is the maximum amount of iron that could be produced from this reaction? And what is the percent yield if the actual mass of iron produced is 300 grams? The first step to completing this problem is to identify what the problem is asking. We need to identify the limiting reagent. This will be either hematite or carbon. We need to calculate the theoretical yield of iron. The actual yield of iron given in the question is in grams. From this it can be inferred that our theoretical yield should be in grams as well. And finally, we need to calculate the percent yield of the reaction. We are given required pieces of information in the problem, such as the mass of hematite and the mass of carbon provided for the reaction and the mass of iron actually produced from the reaction. We need to gather some information that is missing for the problem, such as the molar masses of hematite, carbon and iron. We also need the formula for percent yield. Now that we have all the information required, we can set the problem up using unit analysis. We can find the theoretical yield and limiting reagent in one step. We use the stoichiometric relationship between the reactants and the desired product, in this case iron, to calculate the amount of product that could be produced from each reactant. We set up both equations, making sure that the units cancel and that the stoichiometric conversion for hematite to iron is included. That is, four moles of iron are produced from two moles of hematite. Now that the problem is set up, we can do the calculations and round to the appropriate significant figures. 620 grams of iron could be produced from 100 grams of carbon, and 385 grams of iron could be produced from 550 grams of hematite. This makes the limiting reagent hematite, and the theoretical yield of iron must be 385 grams. Now we can move on to the percent yield. The formula for percent yield is the actual yield, divided by the theoretical yield, multiplied by 100. Remember to use your non-rounded mass of iron in the calculation. The percent yield of this reaction is 77.9%. Now that we have completed the calculations required for this problem, all that is remaining is to write our concluding statement. The limiting reagent and a chemical reaction between 550 grams of hematite and 100 grams of carbon is hematite. The maximum mass of iron that could be produced by this reaction is 385 grams. The actual yield of this reaction, divided by the theoretical yield, gives us a percent yield of 77.9%. This concludes our limiting reagent and yield example. After watching this video, you should be able to determine the limiting reagent and calculate the theoretical yield and percent yield of a chemical reaction.