Effervescence Task

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Re: Effervescence Task

Post by Paradox21 » December 28th, 2010, 7:25 pm

There is an optimum ratio. In theory, you want equal number of moles of reactant, then both get used up completely. For example, if I can only fit 3 grams of baking soda (or some other reactant) into my apparatus, it does me no good to continue to add more and more vinegar. If I put in a gallon of vinegar, there will be an excess of vinegar that does not react. In this case, the limiting reactant is the baking soda. If I want to produce more gas, I will need more baking soda.

You can calculate the number of moles of both substance pretty easily. Sodium bicarbonate has a molar mass of 84.01g/mol. Finding the moles of acetic acid involves finding the percentage of your vinegar that is acetic acid (either by mass or by volume) and using this molarity/molality in conjunction with the molar mass to find the number of moles of acetic acid. Ask a chemistry teacher for help if necessary.
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Re: Effervescence Task

Post by paronomasia » December 29th, 2010, 8:58 am

There's really no point in getting the balloon to inflate as much as possible, just as long as it inflates (enough to trigger the next task, which can be not very much).

If the balloon is still inflating after it has triggered the next task, would that count as a parallel?

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Re: Effervescence Task

Post by paronomasia » December 29th, 2010, 9:15 am

Here are my calculations:

Vinegar = 5% acetic acid by volume
1 L of Vinegar = 1000 mL of vinegar= 50 mL of acetic acid= 50mL * 1.049 g/mL= 52.49 g of acetic acid
Molar mass of acetic acid is 60.05g/mol, so there is 0.874 moles of acetic acid per L of vinegar.
There is 1 mole of acetic acid in 1.144 L of vinegar.




You need 2 moles of acetic acid per one mol of baking soda. So the ratio should be 2.288 L vinegar/ 52.45 g baking soda.

This in turn will produce one mole of CO2 gas, which at STP would be 22.4 L.

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Re: Effervescence Task

Post by Paradox21 » December 29th, 2010, 2:37 pm

Looks good. Except calcium carbonate is not baking soda. Try sodium bicarbonate.
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Re: Effervescence Task

Post by Primate » December 29th, 2010, 8:50 pm

paronomasia wrote:If the balloon is still inflating after it has triggered the next task, would that count as a parallel?
Nope. Tasks can keep running, even after they've triggered the next task.

@paradox, while I suppose calculating the exact stoichiometric ratio isn't a bad idea, I just meant that if you pack in a reasonable amount of vinegar and baking soda, you'll easily produce enough gas.
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Re: Effervescence Task

Post by packercrosbyfan » January 21st, 2011, 8:21 am

The rules don't specify, but I don't know how the judges would be able to tell how strong your vinegar is without a titration setup.

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Re: Effervescence Task

Post by old » January 24th, 2011, 8:57 pm

paronomasia wrote:Here are my calculations:

Vinegar = 5% acetic acid by volume
1 L of Vinegar = 1000 mL of vinegar= 50 mL of acetic acid= 50mL * 1.049 g/mL= 52.49 g of acetic acid
Molar mass of acetic acid is 60.05g/mol, so there is 0.874 moles of acetic acid per L of vinegar.
There is 1 mole of acetic acid in 1.144 L of vinegar.




You need 2 moles of acetic acid per one mol of baking soda. So the ratio should be 2.288 L vinegar/ 52.45 g baking soda.

This in turn will produce one mole of CO2 gas, which at STP would be 22.4 L.
Vinegar can have a very wide range of concentrations of acetic acid. Run of the mill vinegar (the kind you buy at the supermarket) is distilled so it can be any concentration that is convenient and safe. 4-14% is common.

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Re: Effervescence Task

Post by old » January 24th, 2011, 9:21 pm

DeltaHat wrote:The rules only say that the only liquids you can have are water and vinegar. They say nothing about dumping two solids into the water that then dissolve and react. Technically, any aqueous chemical reaction is legal, as long as it's safe.

Also, vinegar is an acid and can be mixed with more than just baking soda.
In addition there is nothing in the rules that say the reaction must be aqueous.

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Re: Effervescence Task

Post by Uncle Fester » January 30th, 2011, 12:26 pm

Saturday, my burning eyes had no problem telling vinegar from acetic acid. Vinegar has acetic acid in it, but acetic acid is not vinegar. Someone tried to convince me that it WAS, so I then asked, "So, I suppose that, by your definition, silicone aquarium sealer is also vinegar?" (acetic acid is the curing agent).

I allowed a citric acid powder reaction because there are no rules concerning solids reacting. I merely addressed safety issues (disposal plans, final product(s) & safety). However, I disallowed one with some kind if acid in water, because the rules oh-so-clearly state that water and vinegar are the only liquids allowed. Bye-bye gas task, bye bye balloon inflation task, add one touch penalty, and all for a reaction that offered no real advantage over one that was legal and argument-proof.
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Re: Effervescence Task

Post by JTMess » February 28th, 2011, 7:34 am

Our team is having quite a bit of trouble with the chemical reaction. We have tried a winch pulling up a balloon filled with baking soda and a pulley, but neither has been reliable at all. How are you guys mixing your baking soda and vinegar consistently? And are most people starting with their balloon on top of a bottle filled with either baking soda or vinegar? We tried to inject vinegar using a syringe but the connection from the syringe to the bottle wasn't completely airtight and the syringe was unreliable to depress even with a heavy weight and a spring. We would really appreciate any help!
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