Is there a specific way to solve limiting reactant problems?

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Ashley Kim
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Is there a specific way to solve limiting reactant problems?

Postby Ashley Kim » Fri Sep 28, 2018 1:01 pm

I found that there were two ways to solve stoichiometric calculations regarding limiting reactants.

The first way is to find the number of moles of each reactant and calculate the mole ratio of the reactants. Personally, I don't use this one because I find it impossible to use with more than two reactants.

The second way is to compare the amount of product that each reactant produces using mole conversions. I find this method a lot easier because you can use it with multiple reactants, and it is less confusing when comparing the amounts (the lesser amount is the limiting reactant). It's a versatile and universal method for these kinds of calculations.

Can I continue using the way I prefer? Or do the professor and TAs care about which method?

Thank you!

Nicolette_Canlian_2L
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Re: Is there a specific way to solve limiting reactant problems?

Postby Nicolette_Canlian_2L » Fri Sep 28, 2018 1:07 pm

The method I use to solve limiting reactant problems is by converting the reactants' mass into moles. I don't think this is impossible because once you have converted the reactants into moles, you compare the two. The reactant with less moles is the limiting reactant. I believe you can solve these kinds of questions either way as long as your work in each step is done correctly.

Ashley Kim
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Re: Is there a specific way to solve limiting reactant problems?

Postby Ashley Kim » Fri Sep 28, 2018 1:11 pm

Thank you! I appreciate it.

Nathan Tran 4K
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Re: Is there a specific way to solve limiting reactant problems?

Postby Nathan Tran 4K » Sat Sep 29, 2018 6:40 pm

The way I solve limiting reactant problems is the way you highlighted in your first description. Converting the grams of reactants to moles allows one to compare the moles of the actual reaction to those in the molecular equation. I understand what you mean about comparing the two values as being confusing, however. I think it may be easier to multiply the moles of one reactant by a factor equal to the moles of the other reactant in the molecular equation. For example, in the balanced equation, CaC2 + 2H2O --> CA(OH)2 + C2H2, we can multiply CAC2 by two to equal the moles of 2H20. In an example where 100 grams of CAC2 interact with 100 grams of H2O, we use stoichiometry coupled with molar masses to realize that these masses are equivalent to approximately 1.56 moles of CaC2 and 5.5 moles of H2O respectively. Simply multiplying the moles of CaC2 by 2 to equal the moles in H20 lets us know that CaC2 is the limiting reactant because 3.12 < 5.5 moles. I agree with the person above though. If you get the same answer every time with your method, then by all means, go for it. Knowing this method on top of your method will only diversify your chem arsenal.

Jim Brown 14B Lec1
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Re: Is there a specific way to solve limiting reactant problems?

Postby Jim Brown 14B Lec1 » Sat Sep 29, 2018 7:06 pm

Nicolette_Canlian_3G wrote:The method I use to solve limiting reactant problems is by converting the reactants' mass into moles. I don't think this is impossible because once you have converted the reactants into moles, you compare the two. The reactant with less moles is the limiting reactant. I believe you can solve these kinds of questions either way as long as your work in each step is done correctly.

This way only works if the mole ratios are the same in the balanced equation. Moles of reactants need to be converted into moles of product in order to accurately and easily compare.


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