Steps for Limiting Reactant Problems

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Salma Sudarmadji 2I
Posts: 21
Joined: Fri Jul 15, 2016 3:00 am

Steps for Limiting Reactant Problems

Postby Salma Sudarmadji 2I » Thu Sep 29, 2016 4:07 pm

Hi, so I just want to make sure I am correct, the general steps for limit reactant calculations is:
1. Balance Equation
2. Calculate molar mass of each reactant
3. Calculate # of moles of each
4. Compare how much of a reactant is needed according to the balanced reaction.

Please comment if I missed anything, thanks!

isabelle ruedisueli 1j
Posts: 21
Joined: Wed Sep 21, 2016 2:56 pm

Re: Steps for Limiting Reactant Problems

Postby isabelle ruedisueli 1j » Thu Sep 29, 2016 4:09 pm

Yes, that sounds correct! You almost always need to convert mass to moles. I went to office hours today and received the same explanation so you are good!

Marisa_Woo_2G
Posts: 24
Joined: Wed Sep 21, 2016 2:56 pm

Re: Steps for Limiting Reactant Problems

Postby Marisa_Woo_2G » Thu Sep 29, 2016 5:58 pm

Looks great! I would just add that these are the steps if the question asked you to find the limiting reactant. If the question asked for the theoretical yield (how much product forms if the reaction occurs perfectly), you would multiply the moles of the limiting reactant by the molar ratio from the chemical equation (Ex: If the reaction was C4H9OH+6O2 --> 4CO2+5H2O, the molar ratio of O2 to H2O would be 6 to 5). This would result in the moles of product that is formed. Finally, since the theoretical yield asks for the mass of the product, you would convert the moles of product to grams of product.

Something else that really helps me remember the steps is the phrase "grams --> mol --> mol --> grams" meaning
After you balance the chemical equation…
1. Grams of reactant converted to moles of reactant
2. Moles of reactant compared to moles of product (to find the limiting reactant)
3. Moles of product converted to grams of product (for the theoretical yield)
Hope this also helps in recalling the steps, but I think you got it down! :)

Katrina_Domingo_3G
Posts: 23
Joined: Wed Sep 21, 2016 2:59 pm

Re: Steps for Limiting Reactant Problems

Postby Katrina_Domingo_3G » Thu Sep 29, 2016 11:20 pm

Can a rxn have two limiting reactants? And is it possible that a rxn has no limiting reactants at all?

Tiffany_Hoang_3C
Posts: 20
Joined: Wed Sep 21, 2016 2:59 pm

Re: Steps for Limiting Reactant Problems

Postby Tiffany_Hoang_3C » Fri Sep 30, 2016 12:21 am

Katrina_Domingo_1E wrote:Can a rxn have two limiting reactants? And is it possible that a rxn has no limiting reactants at all?

A reaction cannot have two limiting reactants. The limiting reactant is the reactant that limits (the most) the amount of product that can be formed. There will be at most one limiting reactant.

However, it is possible that a reaction has no limiting reactants at all, meaning all reactants produce the same amount of product (calculated by using stoichiometry). In this case, no reactant limits the amount of product formed.


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