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Name: David H.
Status: student
Age: 20s
Location: N/A
Country: N/A
Date: 2001 - 2002


Question:
When I mix apple vinegar and arm and hammer baking soda I create a reaction (up to this point i understand what is happening), then I go on to add family dollar store brand iodized salt this creates another reaction. What happen to create this reaction? Is it creating the reaction as if I where to stir it or did it create a completely separate reaction?


Replies:
David,

As you may already know, the first reaction produces bubbles of carbon dioxide (CO2) gas. The CO2 is fairly soluble in water. When you add salt the irregularities and tiny corners on the salt crystals provide nucleation sites on which CO2 bubbles begin to form. In a sense, the salt is driving the dissolved CO2 out of solution. When the bubbles finally grow large enough, they break free and rise through the solution.

The first process (vinegar plus baking soda) is an example of a chemical change. The second process (adding salt to the solution to drive out CO2) is an example of a physical change.

You should be able to produce the same effect with almost any finely granulated material. As an experiment, try a little powdered sugar. Try it to see if sugar is as effective as salt.

Regards,
ProfHoff 365


Hi David,

Question:

When I mix apple vinegar and arm and hammer baking soda I create a reaction (up to this point I understand what is happening), then I go on to add family dollar store brand iodized salt this creates another reaction. What happen to create this reaction? Is it creating the reaction as if I where to stir it or did it create a completely separate reaction?

Answer:

I believe you are correct in the first part of your hypothesis. To my knowledge you are not witnessing a different chemical reaction but you are witnessing a physical reaction. When you added the baking soda to the vinegar you created a large excess of CO2 that is residing in the water. When you added the salt you gave the CO2 saturated solution many more sites in which to bubble off.

This is actually a very good question and as a side note: In chemistry labs chemists that would desire to expedite their chemical reactions, add an inert material called boiling chips to their flasks in order to increase the contact area for reactants to react.

Another side note: This is kind of similar to superheating water in a microwave. If you were to heat water in a VERY SMOOTH glass in a microwave it is quite possible to achieve temperatures above 212 F even at 1 atm pressure. The reason for this is that the water has no imperfections in the glass in order to form a site for a gas pocket to nucleate. I WOULD CAUTION AGAINST TRYING THIS UNLESS YOU HAVE DONE IT BEFORE YOU COULD BURN YOURSELF.

I hope this has been informative,

-Darin Wagner



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