When solving for the limiting reagent, you must convert both of the reactants in a chemical equation to one of the products, using moles. Whichever conversion results in a smaller product, that is the limiting reagent. It is the limiting reagent because once that reactant runs out, the reaction will end and the other reactant will be left in excess. After determining the limiting reagent, you know the other reactant is the excess reagent. You can figure out how much was left in excess by converting the amount of the product that resulted from the previous limiting reagent conversion back to the amount of the excess reagent. Once you discover how much reacted, you can then subtract that number from the original amount and you will know how much is left after the reaction ends.
This picture show the reactants before and after the reaction, distinguishing which is the limiting reagent and what is leftover and alone as the excess reagent.
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| http://www.mhhe.com/physsci/chemistry/chang7/ssg/chap03_9sg.html |
Below is a link that explains limiting and excess reagents and another link with practice problems.
Lilly, thank you for this post! I agree with you, I also prefer to use method two when calculating the limiting reagent. Also, the picture you included is really helpful in helping me understand what exactly is going on in a reaction. Also, thank you for the practice problems that you included, I will surely use these when reviewing for the test :)
ReplyDeleteThis was a great post Lilly! You did a great job summarizing the steps for solving for the limiting and excess reagent. I enjoyed how you posted the steps from class, and also put them into your own words. This made it much more relatable and made it easier for me to walk through. Your links are also great practice, thank you!
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