How to Determine Limiting and Excess Reactants in Chemistry

TL;DR

To determine limiting and excess reactants, balance the chemical equation first. The limiting reactant is identified by finding the one that produces the least amount of product when calculations are done using stoichiometry. To find the excess reactant left over, subtract the amount that reacted from the initial amount of the excess reactant.

Transcript

in this video we're going to go over limiting reactants excess reactants how to find out how much excess reactants left over how to calculate the theoretical yield and the percent yield so let's begin two moles of propane reacts with eight moles of oxygen gas in a combustion reaction how many moles of carbon dioxide are formed so what's the first t... Read More

Key Insights

• ⚖️ Balancing a combustion reaction involves balancing carbon and hydrogen atoms first, then saving oxygen for last.
• 🥳 The limiting reactant is the one that runs out first, and it can be determined by comparing mole per coefficient ratios or calculating theoretical yields.
• ❓ Theoretical yield is the maximum amount of product that can be obtained, and percent yield is the actual yield compared to theoretical yield.

Questions & Answers

Q: How do you determine which reactant is the limiting reactant?

One method is to divide the moles of each reactant by their respective coefficients. The reactant with the lowest mole per coefficient ratio is the limiting reactant.

Q: How do you calculate the theoretical yield?

Theoretical yield can be calculated by converting the moles of each reactant to moles of the product using the molar ratio from the balanced reaction. The reactant that gives the lower value is the limiting reactant and its corresponding theoretical yield.

Q: How do you find the percent yield?

Percent yield is calculated by dividing the actual yield (obtained from the experiment) by the theoretical yield and multiplying by 100.

Q: How do you find the amount of excess reactant left over?

Subtract the amount of the excess reactant that actually reacted from the total amount of the excess reactant. The difference is the amount left over.

Summary & Key Takeaways

• The video explains how to balance a combustion reaction and determine the limiting and excess reactants.

• It demonstrates two methods to identify the limiting reactant: dividing moles by coefficients and comparing theoretical yields.

• It shows how to calculate the theoretical yield of a reaction using stoichiometry and convert it to percent yield.

• Finally, it explains how to find the amount of excess reactant left over after the reaction.