Theoretical, Actual, Percent Yield & Error - Limiting Reagent and Excess Reactant That Remains

The video script begins with an introduction to the concepts of actual yield, theoretical yield, and percent yield in chemical reactions. It explains the formula for calculating percent yield and sets the stage for practice problems involving these concepts. The script also mentions the importance of identifying limiting and excess reactants in a reaction and how to calculate the amount of excess reactant remaining after the reaction.

This paragraph delves into the process of balancing a chemical equation for a combustion reaction involving ethane and oxygen, resulting in carbon dioxide and water. It guides viewers to balance the equation by first aligning carbon atoms, then hydrogen, and finally oxygen. The script then introduces the method for identifying the limiting reactant by comparing the mole ratios of reactants to their coefficients in the balanced equation, concluding that oxygen is the limiting reactant in the given scenario.

The script explains how to calculate the theoretical yield of a reaction by converting the mass of the limiting reactant into the mass of the product using stoichiometric relationships. It details the steps for converting grams of oxygen to moles, then to moles of carbon dioxide, and finally to grams of carbon dioxide. The actual yield is given as the amount of CO2 collected in the experiment, and the theoretical yield is calculated based on the limiting reactant. The difference between theoretical and actual yield is emphasized to understand the efficiency of the reaction.

This section of the script focuses on the calculation of percent yield using the actual and theoretical yields. It provides the formula for percent yield and demonstrates its application with the given data. The concept of percent error is introduced as the complement to percent yield, explaining that the sum of percent yield and percent error equals 100%. The script illustrates how to calculate percent error and emphasizes the relationship between yield and error in chemical reactions.

The script explains how to calculate the amount of excess reactant that remains after a chemical reaction. It uses the example of ethane and oxygen, starting with the limiting reactant (oxygen) and converting its grams into moles of the excess reactant (ethane). The process involves using the molar ratio from the balanced equation and converting moles back to grams. The remaining excess reactant is found by subtracting the amount that reacted from the initial amount present.

This paragraph introduces a new problem involving ethanol and oxygen in a combustion reaction, with a given percent efficiency. The script outlines the steps to balance the chemical equation and explains two methods for identifying the limiting reactant: one based on mole ratios and coefficients, and another based on comparing theoretical yields of products from each reactant. It concludes that oxygen is the limiting reactant and ethanol is in excess, with theoretical yield calculations based on the reactant that limits the production of CO2.

The script provides a method for calculating the actual yield of a reaction based on its efficiency. It demonstrates how to find the actual yield by taking a percentage of the theoretical yield, using the given 85% efficiency as an example. The actual yield is then used to determine the amount of CO2 expected from the reaction. The script also explains an alternative approach using the percent yield formula to find the actual yield from the theoretical yield and vice versa.

The final paragraph wraps up the video by summarizing the concepts of limiting and excess reactants, and how to calculate the amount of excess reactant remaining after a reaction. It reiterates the importance of understanding these concepts for solving stoichiometry problems in chemistry. The script concludes by encouraging viewers to apply these methods to similar problems and thanks them for watching.