Torongo

7+ Year Member
May 24, 2009
48
3
Status
Pre-Medical
So, when carbonated water goes from dissolved carbon dioxide to gaseous CO2, what happens to the delta H?

In my opinion, it should be positive(endothermic) since we are breaking the bonds of carbonic acid( H2CO3) to CO2 and as we know breaking bonds is always endothermic. But the answer says delta H is negative!!

I am really confused, someone please clear my confusion.
 

musafirah

im so cereal right now
Jun 14, 2009
307
0
Status
Medical Student
when thinking about breaking bonds, if the new bonds that form are more stable than the bonds that were broken (in this case the new bonds formed are O=C=O and H2O) then the net reaction is exothermic.

also, carbonic acid is simply CO2 gas dissolved in water. for gases dissolved in water, as temperature increases, the gas is LESS soluble in water, and wants to leave the water into the air (thats why its good to keep soda drinks cold). also when you open a sealed can, the gas CO2 forms and immediately fizzes out of the water because of the partial pressure difference (lower CO2 pressure in the air above the solution).
 
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T

Torongo

7+ Year Member
May 24, 2009
48
3
Status
Pre-Medical
when thinking about breaking bonds, if the new bonds that form are more stable than the bonds that were broken (in this case the new bonds formed are O=C=O and H2O) then the net reaction is exothermic.

also, carbonic acid is simply CO2 gas dissolved in water. for gases dissolved in water, as temperature increases, the gas is LESS soluble in water, and wants to leave the water into the air (thats why its good to keep soda drinks cold). also when you open a sealed can, the gas CO2 forms and immediately fizzes out of the water because of the partial pressure difference (lower CO2 pressure in the air above the solution).
Thanks musafirah for your explanation, I didnt think about it that way; all i was thinking was that we are breaking the bonds of carbonic acid to form carbon dioxide and it must be endothermic! but yeah if the new bonds are more stale then it is exothermic.

One more quick question, carbonic acid has a covalent bond with hydrogen right? but its not just a hydrogen bond or is it?
 

musafirah

im so cereal right now
Jun 14, 2009
307
0
Status
Medical Student
within the carbonic acid the bonds are covalent. the H2CO3 molecules can hydrogen bond with other molecules. not sure what the question is?