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Topic: endo/exothermic bond formation  (Read 13958 times)

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Offline macman104

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Re: endo/exothermic bond formation
« Reply #15 on: January 14, 2009, 03:49:15 AM »
so you are saying an acid water reaction like this:
H2SO4 + H2O → H3O+ + HSO4−
is a TOTALLY exothermic reaction
THAT NO ENERGY IS REQUIRED FOR THIS REACTION TO OCCUR
is that correct?
Correct, simply mixing the two together will release quite a bit of energy.  It can make the water quite warm.  That's why you add the acid to water, because it gets so hot that there is a danger of splattering boiling water/acid at yourself.

Offline benzenejamie

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Re: endo/exothermic bond formation
« Reply #16 on: January 14, 2009, 06:26:19 AM »

[/quote]Correct, simply mixing the two together will release quite a bit of energy.  It can make the water quite warm.  That's why you add the acid to water, because it gets so hot that there is a danger of splattering boiling water/acid at yourself.
[/quote]

okay let me get this straight. the reason you add water to acid is so that it becomes dangerously hot?

Offline Borek

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Re: endo/exothermic bond formation
« Reply #17 on: January 14, 2009, 09:57:21 AM »
It is a little bit more complicated.

When you pour concentrated acid into water it gets hot as well, but the heat is distributed much faster and is generated much more evenly.

When you pour water into concentrated acid, heat is porduced locallyand it doesn't have a time to get distributed, so water may start to boil. That ends in splashes. You don't want splashing hot concentrated sulfuric acid, don't you?
« Last Edit: January 14, 2009, 12:25:20 PM by Borek »
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Offline benzenejamie

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Re: endo/exothermic bond formation
« Reply #18 on: January 26, 2009, 02:40:20 AM »
my friend mr borek...tell me if i am understanding correct...
acid+water
H2SO4 + H2O → H3O+ + H2SO4-
you have a mole to mole reaction
1mol H2SO4 + 1mol H2O produces 1 mol H3O++1 mol of HSO4-
correct?
are you saying that if i had a beaker half-filled with 500 mols of water
and another beaker half-filled with 500 mols of H2SO4-
and i poured the 500 mols of water onto the 500 mols of H2SO4-
that i would get a more violent splashing quicker reaction as opposed to pouring the beaker with the acid onto the water???

Offline Arkcon

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Re: endo/exothermic bond formation
« Reply #19 on: January 26, 2009, 08:34:56 AM »
Yes.  We add sulfuric acid to water, because it's greater density causes it to sink, and the heat generated, at the interface, when it first hits, gets conducted to the surrounding water.  We'd expect, if we just sprinkled water onto sulfuric acid, the water to float, for nanoseconds, then become very hot, then boil.  That would splash the water, and acid around, and could hit someone.  Of course, whether you add acid to water or water to acid, the total energy released is the same, but you knew that, right?
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline benzenejamie

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Re: endo/exothermic bond formation
« Reply #20 on: February 01, 2009, 03:00:35 AM »
and who are you?

Offline Arkcon

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Re: endo/exothermic bond formation
« Reply #21 on: February 01, 2009, 06:27:51 AM »
and who are you?

Ummm...what?

OK.  Here's who I am, so far as anyone on this forum is supposed to know:

http://www.chemicalforums.com/index.php?action=profile;u=17738;sa=showPosts

And here's who you are, so far as I can tell:

Angry questions:
http://www.chemicalforums.com/index.php?topic=30398.msg117415#msg117415

ALL CAPS YELLING:
http://www.chemicalforums.com/index.php?topic=30398.msg115990#msg115990

first off mr mac my second post was not a question. it was simply my own unsubstantiated guess.
and secondly...i am not in a rush for your reply. Many people come on here and throw comments around and never follow them up.
I found it extremely foolish of you to post a comment to a simple question asking me to think about it. Maybe there are people who post things without giving ANY consideration to the answer. But I believe that MOST humans posting here have at least thought about the answer to their question at least ONCE.
It may have been more polite of you to provide an example if you wanted to teach me or lead me in the right direction. You havent even done that in your final answer. You have simply offered me your understanding which for the most part am not sure if it is even correct.

So you're one of the few humans on this forum, and not one of the fools.  Gotcha.

are you going to tell me if i am right or not?
do you even know yourself or do you just like to throw people's question back at them?
do you think i would have posted if i didnt have any doubts or even gave it a little bit of consideration?
 

And on a serious time schedule, it appears
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

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