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Author Topic: The chemical reaction from adding baking soda to vinegar  (Read 3971 times)

paul.fr

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If i am right, this reaction produces no heat. Why is that, don't all chemical reactions produce heat?

If so, what kind of reaction are we looking at?


 

Offline Bored chemist

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The chemical reaction from adding baking soda to vinegar
« Reply #1 on: 15/08/2007 12:17:13 »
NOt all reactions produce heat and this is one that doesn't. In this case the driving force for the reaction is the fact that the gas is given off. Not only does this make the reaction more likely because the reaction can't easily go backwards after the CO2 has left, but the entropy change for the reaction is favourable too.
 

Offline dentstudent

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The chemical reaction from adding baking soda to vinegar
« Reply #2 on: 15/08/2007 12:26:05 »
Is this endo- and exo-thermic reactions?
 

Offline DrDick

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The chemical reaction from adding baking soda to vinegar
« Reply #3 on: 15/08/2007 17:40:24 »
Whether or not a reaction occurs is governed by the Gibbs Free Energy.  This has two parts, (enthalpic and entropic) as shown below:

Gibbs = enthalpic part + entropic part

Enthalpy is the heat basis of the reaction.  If a reaction gives off heat, that's favorable, if it absorbs heat, that's unfavorable.

Entropy is the energy associated with disorder.  If a reaction yields more disorder, that's favorable, if a reaction causes more order, that's unfavorable.

If the two parts are both favorable, the reaction occurs.
If the two parts are both unfavorable, the reaction doesn't occur.

Most times, one part is favorable while the other is unfavorable.  That's where temperature comes in.  Increasing temperature increases the effect of the entropic part, while leaving the enthalpic part almost unchanged.

So, at low temperature, enthalpy wins, while at high temperature, entropy wins.

This explains phase changes, for instance.

Consider liquid and gaseous water.  Liquid water is more favorable enthalpically, because there are more water-water interactions (intermolecular forces of attraction).  However, Gaseous water is more disordered.  Therefore, at low temperature, enthalpy wins and water exists as a liquid.  At high temperature, entropy wins and water exists as a gas.  At some temperature, the enthalpic and entropic effects are equal, and you get an equilibrium situation.  This is the boiling point.

Dick
 

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The chemical reaction from adding baking soda to vinegar
« Reply #3 on: 15/08/2007 17:40:24 »

 

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