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Topic: Limiting reagent problem  (Read 2608 times)

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Offline tarik3001

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Limiting reagent problem
« on: October 24, 2010, 07:22:15 PM »
The determination of weight % SO42- by precipitation with Ba2+ ion to form the insoluble BaSO4 is a well-known method in the wet chemical analysis laboratory.  The reaction proceeds as described by the equation

Ba2+ (aq) +  SO42-  (aq)     to     BaSO4 (s)

A 0.5217 g sample of pure K2SO4 is treated with 30.00 mL of 0.1508 M BaCl2, with the formation of the BaSO4 precipitate.  Determine if enough BaCl2 was added to the solution to precipitate all of the sulfate from the pure potassium sulfate sample.

did I do it right..

.030000L * .1508M BaCl2 = .004524M BaCl2
.5217g K2SO4 * (1/174.262) = .002994 M K2SO4 required

Offline opti384

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Re: Limiting reagent problem
« Reply #1 on: October 25, 2010, 01:01:46 AM »
It seems that you got the calculations right but be careful with "M" because it usually means molarity.

Offline Borek

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Re: Limiting reagent problem
« Reply #2 on: October 25, 2010, 02:56:46 AM »
Just remember you have not answered the question yet.
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Offline Cherriyan

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Re: Limiting reagent problem
« Reply #3 on: November 01, 2010, 10:14:13 AM »
K2SO4 + BaCl2  :rarrow: BaSO4 + 2KCl

Since you need to determine if the volume of BaCl2 added is enough for precipitation of sulphate, you should calculate the number of moles of K2SO4 present and BaCl2 added, then compare the two. If number of moles of BaCl2 >= those of K2SO4, then the BaCl2 is sufficient to carry out the reaction.
According to my calculations, no. of moles of K2SO4 = 0.002998
And no. of moles of BaCl2 is coming ouit to be 0.004524, which is definitely greater than the value mentioned above. So BaCl2 is sufficient to carry out the above precipitation reaction (i.e., sulphate has been completely precipitated)

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