How to Find Limiting Reactant

[Katie 3H]

When we are searching for the limiting reactant, we usually either 1) just find the moles of each reactant and then the one w/ less moles is the limiting reactant or 2) find the moles of reactants, use mole ratios to find the moles of the product through each reactant and then the one who produces less product in moles is limiting reactant. My question is, can we just use method one? How do we know when to use method #2?

[Caden Ciraulo 1J]

Method one only works if there is a 1 to 1 ratio of the reactants present. Otherwise, method 2 is more the correct way to find the limiting reactant as it accounts for the different ratios of moles needed in order to perform a reaction. In other words, finding the lesser amount of moles is only guaranteed to be a limiting reactant if the coefficients of the reactants are the same, so it is often better to utilize a method similar to the second one you explained.

[Katie 3H]

Oh I see. Thank you!

[Neha Mukund]

I ask myself the same question a lot, and I always use method two just to make sure I am not making any mistakes.

[Alejandro Oliva 2F]

Using method #2 is the most effective way of finding the limiting reactants. By including the products in your search you rule out any error by simply using method #1 which sole use is when the ratios are 1-1 between the reactants, which is a scenario that might be quite uncommon in the upcoming midterm and future examples.

[Kaira Shibata 1E]

Method 1 can only be applied if there is a 1 to 1 ratio for the moles of reactant and product being calculated. If it is not a 1 to 1 ratio, you must use the ratio that is represented in the chemical equation.

[Narin Maisha 2H]

I would say to stay safe and make sure that you haven't missed anything, use method two more often or always in comparison to method one. It ensures that you don't overlook a change in ratio based off the coefficients. The first method only works in relation to two compounds that have a 1 to 1 ratio.

[Amanda Tran 1D]

Method 2 will most likely be more applicable for homework/exam problems since that will help you determine theoretical yield, how much reactant is left over, etc. Whereas method 1 will only be somewhat helpful if there is a 1 to 1 ratio, which won't always be the case.

[Parinita Jithendra 2A]

It would be helpful to just use the second method, unless you know that it is a one to one ratio. I have been using the second method for the textbook problems and it has worked for every problem so far!

[Esther Kim]

Method 2 is probably the best one to go with because Method 1 only works if there is a 1:1 ratio.

[Iman Gauhar 3E]

Hi! Method 1 would only work in situations when there is the 1:1 ratio between the limiting reactant and the products. Method 2 is necessary in any equation in which there is a different ratio between the limiting reactant and the products.

[Tylina Guo 1K]

Method 2 is probably the best method to go by. It is the easiest and works all the time, while method 1 only works when the mols ratio is 1:1.

[Kavya Anand 2B]

To find the limiting reactant, convert from the grams/moles of the reactant to the moles of the product. Whichever reactant produces the product with the least amount of moles is the limiting reactant!

[Ellen Brock 2I]

Method two is definitely the more accurate method to use. We want to know the amount that is produced given the moles we already have. So, if there is a mole ration of say 3:2 then we should use method two since it is going to effect the amount produced. As others said, method one is only for 1:1 since there will be no change in moles from reactants to products. Hopefully that makes sense!