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Old 10-17-08, 04:32 PM   #1
Hickeydog
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Need chemistry help

geeze. this chemistry stuff is like the english language: more exceptions than rules. Anyways..

A 27.0 g sample of ethylene glycol, a car radiator coolant, loses 690. J of heat. What was the initial temperature of ethylene glycol if the final temperature is 32.5C? (c of ethylene glycol = 2.42 J/gK)

So. The formula is J=(c)(mass)(change in T). So I solved for Ti and came up with Ti=Tf-J/(c)(mass). And I came up with 21.9 degrees centigrade for the answer. Only problem is, this answer is wrong.

Help. me. Please.
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Old 10-17-08, 04:39 PM   #2
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Help me, jschen Kenobi. You're my only hope.
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Old 10-17-08, 04:58 PM   #3
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You have the change in T correct, but think about the question. If it loses heat, should the initial temperature be higher or lower than the final temperature?
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Old 10-17-08, 04:59 PM   #4
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do you have a selection of answers?
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Old 10-17-08, 05:01 PM   #5
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42
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Old 10-17-08, 05:01 PM   #6
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No selection of answers. And I tried + and -. both are wrong.
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Old 10-17-08, 05:02 PM   #7
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42
42. what? I need that decimal..
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Old 10-17-08, 05:04 PM   #8
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42 is the answer to everything....ohh boy...you've a lot to learn and i've alot to teach.

< snaps fingers > now get back to working on that chemistry!!
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Old 10-17-08, 05:06 PM   #9
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yeah. I entered in the 42 and I got within 10% of the correct answer. So 29.1 is definitely out. And I think it's positive.
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Old 10-17-08, 05:08 PM   #10
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I said you already have the change in temperature correct. Just go the other way.

It's 32.5 plus the difference between 32.5 and your 21.9 answer. I feel...wrong...just giving it to you.
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Old 10-17-08, 05:09 PM   #11
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never mind. I figured it out.

GOD I FLIPPING HATE CHEMISTRY!!!!! GGGGGGGGGGAAAAAAAAAAAHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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Old 10-17-08, 05:10 PM   #12
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I said you already have the change in temperature correct. Just go the other way.

It's 32.5 plus the difference between 32.5 and your 21.9 answer. I feel...wrong...just giving it to you.
And giving the answer to me would be like giving a crippled guy (such as my proffessor soon-to-be) a wheelchair.
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Old 10-17-08, 05:12 PM   #13
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43.06
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Old 10-17-08, 05:14 PM   #14
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This is algebra, not chemistry. It's all about the units/labels.
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Old 10-17-08, 05:14 PM   #15
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yea...how dang hard was it to get 43.06. that's waht i got too.
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Old 10-17-08, 05:17 PM   #16
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never mind. I figured it out.

GOD I FLIPPING HATE CHEMISTRY!!!!! GGGGGGGGGGAAAAAAAAAAAHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
But this really isn't a chemistry problem. It's just a very simple algebra problem, and it is stated more in terms of physics than chemistry, anyway.
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Old 10-17-08, 07:54 PM   #17
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Help me, jschen Kenobi. You're my only hope.
People who want help should show their work and explain all their reasoning. And try not to post questions the day after jschen had a long night. But then, who knew that I would end up spending 6 hours at a bar on a Thursday night when I went alone just to grab a quick dinner?
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Old 10-17-08, 10:18 PM   #18
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I knew. I called ahead and told the bartender you were coming in.
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Phobias are for irrational fears. Fear of junk ripping badgers is perfectly rational. Those things are nasty.
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Old 10-17-08, 11:07 PM   #19
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No wonder they didn't seem shocked!
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