Limiting Reactant given masses

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Elle_Bertuccelli_1B
Posts: 24
Joined: Sat Jul 09, 2016 3:00 am

Limiting Reactant given masses

Postby Elle_Bertuccelli_1B » Tue Sep 27, 2016 7:12 pm

When finding a limiting reactant, what if the mass of only one reactant is given?

E.x. Consider the unbalanced reaction: PCl3+ H2O --->HCl + H3PO3 What mass of HCl is produced by the reaction of 23.6g of PCl3?
I'm confused because the grams of PCl3 is given, but there is no amount given for H20.

Amy_Bugwadia_3I
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Joined: Wed Sep 21, 2016 2:56 pm
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Re: Limiting Reactant given masses

Postby Amy_Bugwadia_3I » Tue Sep 27, 2016 7:23 pm

I am not positive about this, but I think that if you aren't given the mass of the second reactant, you should assume that the reactant with the given mass (in this case, PCl3) is your limiting reactant. Then, solve it as you would any other limiting reactant problem by first always remembering to balance the equation. Next, convert grams of PCl3 to moles, and multiply according to how many moles of HCl correspond to one mole of PCl3 based on the balanced equation. Finally, convert moles of HCl to grams.

Makenna Vulgas 1G
Posts: 20
Joined: Wed Sep 21, 2016 3:00 pm

Re: Limiting Reactant given masses

Postby Makenna Vulgas 1G » Wed Sep 28, 2016 1:37 pm

I agree that PCl3 in this case is the limiting reactant. It would be very hard, if not impossible to find the specific mass of the reactant H20 without it being a given quantity or having more information in the problem. Maybe it is assumed that more H20 reactant could be added to the reaction if necessary since they didn't give a specific mass for it. Therefore it wouldn't be "limiting" but thats just a guess. I would just say work with what you are given and Amy did an awesome job describing the step by step process of what to do with the mass of PCl3. If the problem really warranted for finding a limiting reactant, both masses would be given and more in depth evaluation would be required.


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