Bicarbonate of soda in The AnswerBank: How it Works

Bill_lpool

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

Clanad

Check here for a full description as well as some other interesting experiments for kids:

http://www.wvu.edu/~exten/infores/pubs/fypubs/wl290.pdf

mimififi

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?

brachiopod

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 !!

mimififi

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.

Cmitchell

I've found 4 or 5 versions of nigellas Hokey Pokey (cinder toffee) recipe(it's the stuff in the middle of crunchie bars). I saw her make it on the telly last chrismas I think.. I have not made it and I have found various versions as stated.

Be careful not to burn yourselves And do use a sugar thermometer. Also most peoples comments say at least 3 minutes.

Good luck

75g/2�oz caster sugar
30ml/1�fl oz golden syrup
30g/1�oz bicarbonate of soda

1. To make the honeycomb, place a heavy-bottomed saucepan on the hob and heat the caster sugar and syrup until the sugar melts and caramelises.
2. Add the sifted bicarbonate of soda and stir well when it starts to bubble. Pour the mixture onto a greased baking tray and allow to cool

Please be extremely careful. You have to cook the sugar up to a high temperature and then add bicarbonate, but it will immediately foam up and there is a real risk of bad burns if you are in the least bit careless

Cmitchell

8 oz sugar, small pinch of cream of tartar, 1 tbsp golden syrup, 2.5 fl ox water, 1/4 tsp bicarbonate of soda, 1 tsp warm water, greased tin.
Heat together sugar, cream of tartar, syrup and cold water till sugar has dissolved.
Boil without stirring till mix reached 310 deg F (my old sugar thermometer is scaled in F not C, sorry) then remove from heat.
Mix bicarb with the warm water and add to the boiling toffee.
Stir gently and pour at once into greased tin.
Mark into squares and break when cold.

She omitted the acid!

Take:
1lb (450g) Granulated sugar
�pt (300ml) Water
4tbsps (60ml) Vinegar
� level tsp (2.5ml) Bicarb

Grease a tin 12"x4" (30cmx10cm)
Dissolve the sugar in the water and vinegar in a deep heavy-bottomed pan. Bring to boiling point and boil gently to soft-crack stage (285F or 141C). Take from the heat. Remove any lumps from the bicarb and add to the toffee; stir well to mix thoroughly and pour into prepared tin. Mark into squares or fingers when half-set. This makes about 1lb (450g).

DO NOT smash it into little bits like Nigella, the "golden dust" sticks to everything when you are trying to eat it.

I think her actual recipe might be on this page

http://www.foodnetwork.com/recipes/nigella-law son/hokey-pokey-recipe/index.html

and you can veiw more comments about how easy/hard people have found it here

http://www.foodnetwork.com/recipes/nigella-law son/hokey-pokey-recipe/reviews/index.html

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Bicarbonate of soda

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