UnderstandingMoles
2 Masses of reactants A & B
How is this done?
Why is this done?
Moles of each substance
How is this done?
Limiting reactant identified
Amount of leftover excess reagent
Percent Yield
Concept of Moles
A "mole" is similar to a "dozen" in the sense that it refers to a fixed number of objects. A "dozen" is 12 things while a "mole" is 6.022 x 10^23 things. Click on and read through this example, and then swap out the word "dozen" for the word "mole." The logic will still apply. Scientists needed a unit like "a dozen" to work with, but a dozen would be far too small of a count for atoms/molecules, given how small they are. We needed a bigger number, which was chosen to be 6.022 x 10^23. If you're curious, ask your professor why this number was chosen :)
How to determine limiting reagent?
First using simple stoichiometry, you want to figure out how much product (in moles) will form with the amount of of reactant A that is given (in moles of course), and then find the same for reactant B. - Click here to see how this step is done Next, compare the amounts. The reactant that creates the least amount of product is the limiting reactant (click here to understand why), and the amount of product created by it is the theoretical yield
Mass <--> Mole conversion
To get from the mass of a sample to the amount of moles (or the other way around), use the Molar Mass as the "bridge" between the two.
Think: "MOLE OR MASS" - Molar mass can go between the two (as long as you have one of them)
Why do we need to go from mass to moles?
When seeing how much of one chemical is needed to react with/is produced from a certain amount of another chemical, we need to use moles. It is a common mistake to assume something like "one gram of hydrogen atoms will completely react with one gram of fluorine atoms to make HF," however this is incorrect. Since the mass of a fluorine atom is much greater than that of a hydrogen atom (roughly 19x greater), a gram of fluorine has far less atoms in it than a gram of hydrogen. Think of it this way: A box containing 100 pounds of bowling balls has a lot less balls in it than a box containing 100 pounds of golf balls.
2 Masses of reactants A & B
Dj Templeton
Created on October 18, 2025
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Transcript
UnderstandingMoles
2 Masses of reactants A & B
How is this done?
Why is this done?
Moles of each substance
How is this done?
Limiting reactant identified
Amount of leftover excess reagent
Percent Yield
Concept of Moles
A "mole" is similar to a "dozen" in the sense that it refers to a fixed number of objects. A "dozen" is 12 things while a "mole" is 6.022 x 10^23 things. Click on and read through this example, and then swap out the word "dozen" for the word "mole." The logic will still apply. Scientists needed a unit like "a dozen" to work with, but a dozen would be far too small of a count for atoms/molecules, given how small they are. We needed a bigger number, which was chosen to be 6.022 x 10^23. If you're curious, ask your professor why this number was chosen :)
How to determine limiting reagent?
First using simple stoichiometry, you want to figure out how much product (in moles) will form with the amount of of reactant A that is given (in moles of course), and then find the same for reactant B. - Click here to see how this step is done Next, compare the amounts. The reactant that creates the least amount of product is the limiting reactant (click here to understand why), and the amount of product created by it is the theoretical yield
Mass <--> Mole conversion
To get from the mass of a sample to the amount of moles (or the other way around), use the Molar Mass as the "bridge" between the two.
Think: "MOLE OR MASS" - Molar mass can go between the two (as long as you have one of them)
Why do we need to go from mass to moles?
When seeing how much of one chemical is needed to react with/is produced from a certain amount of another chemical, we need to use moles. It is a common mistake to assume something like "one gram of hydrogen atoms will completely react with one gram of fluorine atoms to make HF," however this is incorrect. Since the mass of a fluorine atom is much greater than that of a hydrogen atom (roughly 19x greater), a gram of fluorine has far less atoms in it than a gram of hydrogen. Think of it this way: A box containing 100 pounds of bowling balls has a lot less balls in it than a box containing 100 pounds of golf balls.