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Topic: ap chemistry- acid base problems  (Read 8321 times)

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Offline gotalbin

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ap chemistry- acid base problems
« on: January 03, 2008, 05:47:46 PM »
what volume of .1 M strongly acidified potassium permanganate (KMnO4+H2SO4) solution is required to oxidize 1.66 of C8H6O4?

I know the first thing I have to do is write the reaction equation. All I got is C8H6O4 + KMNO4 + H2SO4 ---------------------------> ?

I dont know what the products would be....could somebody help me? thanks
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Offline Alpha-Omega

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Re: ap chemistry- acid base problems
« Reply #1 on: January 03, 2008, 06:15:49 PM »
That is phthalic acid (terephthalic acid):  C8H6O4


C8H6O4 / C6H4(COOH)2. Molecular mass: 166.1

Picture attached
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Offline Borek

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Re: ap chemistry- acid base problems
« Reply #2 on: January 03, 2008, 06:21:48 PM »
Quote from: Alpha-Omega on January 03, 2008, 06:15:49 PM
That is phthalic acid (terephthalic acid):  C8H6O4

It CAN be phthalic acid. And many other compounds as well. Question as posted doesn't make sense to me, unless we are to assume oxidation goes to the very end.
« Last Edit: January 17, 2012, 10:43:26 AM by Arkcon »
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Offline Alpha-Omega

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Re: ap chemistry- acid base problems
« Reply #3 on: January 03, 2008, 06:50:31 PM »
Here is the reaction:

KMnO4 + C8H6O4 + H2SO4 -----> MnSO4 + CO2 + H2O + K2SO4   

Now find what is oxidized and what is reduced
Balance the charges...
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Offline Alpha-Omega

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Re: ap chemistry- acid base problems
« Reply #4 on: January 03, 2008, 07:03:12 PM »
OK OK...most common...first thing came to mind....
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Offline Alpha-Omega

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Re: ap chemistry- acid base problems
« Reply #5 on: January 03, 2008, 07:17:20 PM »
The molecular mass of C8H6O4 = 166.1 and need to oxidize 1.66 g of that mass and 166.1/100 = 1.66
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Offline Alpha-Omega

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Re: ap chemistry- acid base problems
« Reply #6 on: January 03, 2008, 07:25:14 PM »
Assuming the oxidation goes to completion: 

(5e- + Mn --> Mn) reduction     ( +1 +7 -2)   and get (+2+6-2) charges
 5 (C+3 --->.C+4 + e-) oxidation    (+1+3-2) and get   (+4-2) charges

if I have NOT made a MISTAKE...
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Offline Borek

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Re: ap chemistry- acid base problems
« Reply #7 on: January 04, 2008, 03:20:42 AM »
Quote from: Alpha-Omega on January 03, 2008, 06:50:31 PM
KMnO4 + C8H6O4 + H2SO4 -----> MnSO4 + CO2 + H2O + K2SO4  

Now find what is oxidized and what is reduced
Balance the charges...

No charges here. You probably refer to oxidation numbers. Even then - where does +3 for carbon come from?
« Last Edit: January 17, 2012, 10:43:47 AM by Arkcon »
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Offline Alpha-Omega

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Re: ap chemistry- acid base problems
« Reply #8 on: January 04, 2008, 08:31:30 AM »
yes OXIDATION STATES they are charges carried by the species in the equation...and not the same as a charged complex...and we were taught to balance the masses and charges in a REDOX equation....so you can take on the entire education system if you like....masses not meaning grams...masses referring to the coefficients...MOLES/MOLAR....whatever word you prefer-and oh yes because species react mole to mole and not gram to gram....

Too Early in the morning for all this...
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Offline Borek

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Re: ap chemistry- acid base problems
« Reply #9 on: January 04, 2008, 02:55:07 PM »
Quote from: Alpha-Omega on January 04, 2008, 08:31:30 AM
yes OXIDATION STATES they are charges carried by the species in the equation

No, they are numbers assigned to atoms to help in charge accounting, they have nothing to do with the real world. That's why many teachers prefer to teach half-reaction method. Still, nothing wrong with using ON as long as you don't treat them too seriously and you don't assign them meaning they don't have.
« Last Edit: January 18, 2012, 09:16:47 AM by Arkcon »
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Offline Alpha-Omega

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Re: ap chemistry- acid base problems
« Reply #10 on: January 04, 2008, 06:46:09 PM »
Easier for me to keep track using the half-rxn method...
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Offline PanCerowany

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Re: ap chemistry- acid base problems
« Reply #11 on: March 05, 2010, 08:52:28 AM »
Permagnanate is not strong enough to oxidize everything to CO2. Many compounds will easily sutrvive.
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