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Chemistry help

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whoa-dere
Posts: 10596 - Karma: 7,103

Use bond enthalpies (Table 8.4 in the textbook) to estimate the enthalpy change for each of the following reactions.
I keep getting -80 but the answer is -416??!??!?!?!
H2O2(g)+2CO(g)→H2(g)+2CO2(g)
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Nov 16 2013 4:37PM
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MilaKunis
Posts: 1480 - Karma: 3,646
Ill help when I get back to my room
Nov 16 2013 4:41PM
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Mrepicbro
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Nov 16 2013 4:43PM
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MilaKunis
Posts: 1480 - Karma: 3,646
4 CO double bonds on the right side with 1 H single bond. Then left is 2 CO triple bonds and 2OH bonds and one OO bond
Nov 16 2013 4:54PM
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Darth.Maul
Posts: 2472 - Karma: 652
Products-reactants
You have 2 CO2's whoch is 4 CO double bonds and a H2 single bond on the product side.

You have 2 CO's which gives 2 CO triple bonds and H2O2 which gives 2 OH bonds and a OO single bond.

I cant read the numbers on the chart of bond enthalpies but that should be the way to figure out which numbers to use from the chart. You can draw lewis structures to determine the number of bonds between the atoms in each compound.
Nov 16 2013 4:59PM
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MilaKunis
Posts: 1480 - Karma: 3,646
Too late nerd
Nov 16 2013 5:01PM
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Darth.Maul
Posts: 2472 - Karma: 652
Damn my touchscreen mobile device for being too slow.
Nov 16 2013 5:02PM
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*DUMBCAN*
Posts: 2447 - Karma: 5,628
Full solution. This took me way too long considering I'm a chemistry major... The last time I did one of these was four years ago, I'll use that as my admittedly dreadful excuse.

Three things have been cut off in the top-left - a hydrogen atom, and the other two read 1 x... Also that giant bracket in the bottom left shouldn't be that big...

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Nov 16 2013 5:03PM
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MilaKunis
Posts: 1480 - Karma: 3,646
I'm in the same boat. I struggled to write the uppercase letters without yelling at him.
Nov 16 2013 5:04PM
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whoa-dere
Posts: 10596 - Karma: 7,103
oh lol i thought the CO was just a single bond. thanks guyzzzzz
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Nov 16 2013 10:11PM
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marsh.
Posts: 1173 - Karma: 1,403
Chem 103 sucks
Nov 17 2013 12:10AM
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whoa-dere
Posts: 10596 - Karma: 7,103
do you have nathanson?
Nov 17 2013 1:49AM
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Bombogenesis
Posts: 1984 - Karma: 4,006
So glad I'm done with school and specifically the fucking chem sequence
Nov 17 2013 2:07AM
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marsh.
Posts: 1173 - Karma: 1,403
Nah brunold
Nov 17 2013 2:10AM
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chicken
Posts: 6843 - Karma: 2,123
that's pretty bad. although I am in fourth year physics and can't count in crib.
Nov 17 2013 11:47AM
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Wompuscat
Posts: 818 - Karma: 380
Meh, all this crap in chem sucks. Hated Principles 1 and 2. Organic Chem is so much more fun. And way easier if you ask me. Actually learn the reactions though, most people just memorize shit. If you actually understand how the molecules flow and move, it makes the class so easy.
Nov 17 2013 12:50PM
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jb616
Posts: 163 - Karma: 92

Nov 17 2013 1:01PM
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*DUMBCAN*
Posts: 2447 - Karma: 5,628
Well... I think you should just push through and learn principles. It's boring of course, but it helps so much. Though that all depends on what you're planning on doing with chemistry, if you're not taking it further it probably doesn't matter. If you hate principles then you'd hate chem at university, it's 90% principles.
Nov 17 2013 1:05PM
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Wompuscat
Posts: 818 - Karma: 380
I'm a senior at the University of Iowa. I've taken Principles 1 and 2 with lab, Organic Chem 1 and 2, and a seperate Organic chemistry Lab. I'm also currently in biochemistry. I was going to take advanced organic chemistry this semester but opted for human pharmacology. I finished Principles 1 and 2 my freshman year of college, and have never used it since. I have to review it for the MCAT, but as a person that almost got a chemistry minor, I can say push through Principles of chem, but it is nowhere near 90% of what you learn at the university.
Nov 17 2013 1:21PM
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MilaKunis
Posts: 1480 - Karma: 3,646
I though biochemical major gaurenteed Chem minor
Nov 17 2013 1:23PM
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Wompuscat
Posts: 818 - Karma: 380
I'm a human physiology major with pre-med intent. I take the chem courses for the pre-med, and biochem I'm in just because it's fun. I should have majored in biochem, but I'm not switching now.
Nov 17 2013 1:31PM
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MilaKunis
Posts: 1480 - Karma: 3,646
Oh alright makes sense
Nov 17 2013 1:33PM
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*DUMBCAN*
Posts: 2447 - Karma: 5,628
Depends how you apply what I said. I meant it like: 'good understanding of principles will make 90% of the course significantly easier to understand.'.

Examples: group theory, stereochem, pretty much all main group chemistry (a lot of inorganic), crystal structures (a lot more of inorganic), etc... I could go on for a while. The main question is where in chemistry do principles not really help as much? Theoretical chemistry, quantum mechanics, statistical thermodynamics stand out for me. These (ST excluded) are the fundamentals of principles, so principles are really the answer to TC and QM.
Nov 17 2013 1:40PM
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a_pla5tic_bag
Posts: 9215 - Karma: 5,398
probably cause there's no/little math. If any of you really want to to do serious chemistry, get very very good at math.
Nov 17 2013 1:42PM
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*DUMBCAN*
Posts: 2447 - Karma: 5,628
Yep. I'm after a masters in stat thermo, I know this well.
Nov 17 2013 1:45PM
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