Hi,
I am doing an experiment with my boy (making a volcano actually) and we are going to be mixing bicarb with vinegar (for the eruption of course!).
Why do these two chemicals react in this way; what is the science behind the magic? Also, if anyone knows the chemicular equation for this and if any biproducts are produced that would be good too. Also, what else can you use bicarb for other than whitening your teeth' keeping cabbage green when you cook it and making fake molten lava?
mimififi Fri 21/10/05 15:00
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Hi,
the acetic acid (vinegar) reacting with the bicarb first produces sodium acetate and carbonic acid.
HC2H3O2 + NaHCO3 ===> NaC2H3O2 + H2CO3 (unbalanced)
The carbonic acide then decomposes to water and carbon dioxide
H2CO3 ===> H2O + CO2
and so the total equation for the reaction missing out the mid step is
NaHCO3 (aq) + 2 HC2H3O2 (aq) -> H2O (l) + CO2 (g) + 2NaC2H3O2 (aq)
The reason why both react is because acetic acid is an acid and bicarb is a baseand these always react producing a salt and water.
Laters
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Question Author
COOL. That's great, and I'm impressed with the ever prompt replies, I had barely finished clickity-clicking when 'ding-dong-you got mail' pops up....You guys are so good.
I shall be explaining this to my son tomorrow as we re-enact Pompeii. Will red food colouring added to the mixture (for the purposes of authenticity) have an impact on the reaction???
And presumably, the whole carbonic acid thing is safe and is not going to rot our flesh?
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TOTALLY safe, mimififi. The most corrosive substance involved int his reaction is ethanoic acid.... that's vinegar to you and I.
I used to do 'volcano' demonstrations with potassium dichromate. It's an orange, crystalline powder (a bit like orange coloured sugar), that, when heated, produces about ten times as much grey-green ash, with lots of sparks and much glowing. I built my own subduction zone, and the stuff was electrically heated at the flick of a switch.
Aarrr, those were the days - not allowed to demonstrate it in schools now - Health & Safety, COSHH and fume cupboards have seen to that. No wonder the kids think science is boring.
Even with vinegar / sodium hydrogen carbonate volcanoes you have to do full risk assesments etc - despite the fact that the kids are more likely to splash acid (ie. vinegar) in their eye when sprinkling it on their chips !!
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Question Author
oh I know Brachiopod! I used to be an English lit teacher in a secondary school, and such was the risk assessment paperwork and the insurance and the coach stuff etc etc etc that I just didn't bother with theatre trips in the end. It took nearly a whole school year to get trips to the theatre approved by the managemnt (or mis-management to you and I) and the board of govs!!! What a head ache. No wonder kids hate shakespeare, you can't read shakespeare, you have to see it!
Thanks for help with the experiment. We did it this morning, and he was a little dissappointed and said he thought it was going to be an actual volacnic eruption with flying debris....I perhaps shouldn't have been so description when explaining an actual volcanic erruption!, but he did enjoy the mixing up of the stuff and the seeing it reduce again. He loves science and I do try to keep it practical. He has a very go-and-find-out kinda brain so text book science is a bit of a no-no at the moment, but then he is only 7 and I'm trying to keep it fun. We will try some of the stuff on the site Clanad sent too and we did frogspawn this year too and he loved that. We are also growing crystals (not very successfully, sugar crystals are a bit slow), I'm trying to document with photographs and a few written notes as he finds the note taking on the onerous side, writing is not his strong point. That is working well
Any other tips for teaching science and cool stuff to do with household chemicals/substances would be great if have any ideas, it would be great to hear them
Thanks for all you help guys, it was much appreciated.
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