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Q wrote on 2013-04-04 19:00
[Image: http://puu.sh/2tPvf]
Was doing some practice problems and got stuck on part C and D. The answers for the previous sections are:
2a) 0.00608 mol
b) 1.2 atm
c)1 atm O2 Consumed. (got from answer key)
For Part C, I don't even know what's going on in the answer key
For the chemical equation in part D, I got the ratio for hydrocarbon : O2 : H2O : CO2 to be 1 : 6 : 3 : 4 (this is disregarding the formula for hydrocarbon, i'm just trying to get the coefficients right since that seems to be where i'm having trouble...).
The answer is supposed to be 1 : 5 : 3 : 4
Answer key:
http://apcentral.collegeboard.com/apc/public/repository/ap12_chemistry_scoring_guidelines.pdf
(question 2 btw)
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Q wrote on 2013-04-04 19:21
Well. I found a method to solve it, but would like for someone to check/confirm my reasoning etc works:
1 mol O2 will produce 0.5 mol of H2O and 1 mol of CO2 since O2 is the only contributor to the oxygen in either one. So knowing that there's 0.6 atm of CO2 and 0.8 atm of H2O, and going by the fact that partial pressure is 1:1 with mols, we can say there's 1 atm of oxygen consumed, solving part C.
For part D, we know 1 atm oxygen and 0.2 atm hydrocarbon is consumed to produce 0.6 atm CO2 and 0.8 atm H2O, so we just divide the limiting reactant's partial pressure out, get the ration 5 oxygen : 1 hydrocarbon : 3 CO2: 4 H2O, then convert to mols for the correct chemical equation.
Is my reasoning right?
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Fumika wrote on 2013-04-04 19:51
Oh shoot.... It's been a really long time since I've laid my eyes on this exam, the last time was the day right after I took it
:cry::cry:
Anyway, if my rusty knowledge is still in working order, your reasoning sounds about right to me. I think I did the same thing, except, I just compared the proportions rather than dividing by the limiting reagent.
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Elvira wrote on 2013-04-04 20:05
:!!:
eeeeeeeeeeeeeeeeeeeeeeeeeehh..
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Kenny? wrote on 2013-04-04 20:45
I looked at my notes from last year and I think your method seems about right-
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Q wrote on 2013-04-05 02:57
Thanks all~ alright then. i guess there's a chance i'm not failing the exams this year ahhh.
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Sumpfkraut wrote on 2013-04-05 12:40
Is rxn seriously the standard abbreviation for reaction?
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BobYoMeowMeow wrote on 2013-04-05 12:49
Quote from Sumpfkraut;1063374:
Is rxn seriously the standard abbreviation for reaction?
yes
Chemists use all sorts of abbreviations and shortcuts like n for the number of moles or abbreviate moles as mol
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Sumpfkraut wrote on 2013-04-05 12:53
Yeah but just replacing actio with x? ._.
That's so... I dunno. Weird. Not as weird as X-Mas, but still.
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Aubog007 wrote on 2013-04-07 10:13
Wow, i completely forgot how to do all of this, 8 years is far too long without refreshers.
This makes me want to read my college text books i still have, unfortunately time no longer exists
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Sumpfkraut wrote on 2013-04-07 14:21
Why, do you need it? Or do you have a special interest in chemistry?
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Aubog007 wrote on 2013-04-07 16:19
Quote from Sumpfkraut;1064419:
Why, do you need it? Or do you have a special interest in chemistry?
I have an interest in chemistry.
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Sumpfkraut wrote on 2013-04-07 17:07
Then that is a reasonable goal!
Also this is sort of relevant.
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[Image: http://puu.sh/2vHPJ]
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