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shadyy
aHhahhHA



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brain fart - chem help
#22363556 - 10/11/15 02:19 PM (8 years, 3 months ago) |
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A chemist placed a 0.7902 g sample of potassium permanganate, KMnO4 (molar mass = 158.03 g/mol) in a volumetric flask and added water to make 100.00 mL of a potassium permanganate stock solution. She then used a volumetric pipet to transfer a portion of this stock solution to a volumetric flask and added water to make 500.00 mL of a 2.500 x 10–3 M diluted KMnO4(aq) solution. She used this diluted solution to titrate 25.00 mL of a 1.000 x 10–2 M solution of Pb(NO3)2(aq), according to the following, balanced equation:
2 H2O(l) + 2 KMnO4(aq) + 5 Pb(NO3)2(aq) -> 5 PbO2(s) + 2 Mn(NO3)2(aq) + 2 KNO3(aq) + 4 HNO3(aq)
After the titration was completed, she filtered off the solid PbO2(s) (molar mass = 239.2 g/mol) that had formed, dried it and found the mass to be 0.0508 g.
What is the theoretical yield of PbO2?
I got 0.02392g which gets me partial credit, but I'm curious how to get the right answer? Please don't post with no explanation!
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LogicaL Chaos
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Re: brain fart - chem help [Re: shadyy]
#22363647 - 10/11/15 02:42 PM (8 years, 3 months ago) |
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Giftofdeprivation
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Re: brain fart - chem help [Re: shadyy]
#22363674 - 10/11/15 02:45 PM (8 years, 3 months ago) |
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:oopswrongforum:
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akira_akuma
Φύσις κρύπτεσθαι ὕψιστος φιλεῖ


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it looks like a simple math problem, but i don't know shit-fuck-all about math or molarity - so i'm sorry i can't help, but i appreciate the topic, it sounds interesting. hope you get your answer OP, and BTW, hope i didn't make you think you had the answer yet...someone will come along i'm sure.
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shadyy
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Re: brain fart - chem help [Re: akira_akuma] 1
#22364127 - 10/11/15 04:18 PM (8 years, 3 months ago) |
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It's cool. Figured it out..
M = mol solute/L solution
KMnO4 (2.500 x 10^-3) (.500L) = 0.00125 mol/L
Pb(NO3)2 (1.000 x 10^-2) (.025L) = 0.00025 mol/L
Therefore, Pb(NO3)2 is the limited reactant..
0.00025 x 239.2 = 0.0598g PbO2 <--- answer
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akira_akuma
Φύσις κρύπτεσθαι ὕψιστος φιλεῖ


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Re: brain fart - chem help [Re: shadyy]
#22364134 - 10/11/15 04:19 PM (8 years, 3 months ago) |
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nice job.
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shadyy
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Re: brain fart - chem help [Re: akira_akuma] 1
#22364151 - 10/11/15 04:22 PM (8 years, 3 months ago) |
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lol thanks...once it clicks, I'm good. It's getting it to click that's the tricky part.
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blackhawk
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Re: brain fart - chem help [Re: shadyy]
#22364156 - 10/11/15 04:23 PM (8 years, 3 months ago) |
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what chemistry is this?
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shadyy
aHhahhHA



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Re: brain fart - chem help [Re: blackhawk]
#22364163 - 10/11/15 04:24 PM (8 years, 3 months ago) |
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just gen chem I
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