Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: iDino on June 01, 2009, 06:18:51 PM
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Okay so Im not doing to well in Chem, and I need help on this project please.
We are given a 1 quart ziplock. We have to figure out how much of the 2.75M HCl and how much NaHCO3 to add to the bag to fill it completely, without popping the bag. If it pops (given 2 trials) we fail. If it doesnt fill all the way, we loose a lot of points... Now I was able to figure out the reaction.
NaHCO3 + HCl --> NaCl + H2O + CO2
Now Im stuck! Im absolutely lost. I need to figure out how to get the right amount of CO2, and I need the temp of the room, and the pressure as well. But now Im lost. Do I use Gas Laws? Im stuck!!
Can any one help me out with setting this up? I cannot afford an F...
I think after a good nudge, Ill be pretty good.
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Yes, ideal gas equation is what you need.
Pressure - atmospheric.
Temperature - probably between 20-25 deg C.
What is a bag volume?
How many moles of CO2 will it hold?
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OOHHH okay!! thanks a lot!
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okay so I use PV=nRT
so (pressure of the day)(1L right? 1qt=1L) = (n-I have no how to find moles)(8.31 kpa*L/mol*K)(Temp of the day)
I need the n, dont know how to figure it out..
ANd I would use 1 Liter as my volume right? Because thats how much the bag holds.
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At room temperature and pressure, 1 mol of Carbon Dioxide will have a volume of 24 dm3. You can find out how many moles you produce by knowing the mass of bicarbonate and the amount of acid you add.
Pressure of the Day may not be entirely relevant - you need to know the maximum pressure that the bag can withstand. Once you seal the bag, the air pressure inside is equal to that outside, unless you squeeze or stretch it to change the volume. Otherwise, you're good to go.
Just remember to use Kelvin instead of Farenheit or Centigrade for the Temperature of the day!
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okay so I use PV=nRT
so (pressure of the day)(1L right? 1qt=1L) = (n-I have no how to find moles)(8.31 kpa*L/mol*K)(Temp of the day)
I need the n, dont know how to figure it out..
ANd I would use 1 Liter as my volume right? Because thats how much the bag holds.
1 litre is not the same as 1 quart. But what the conversion factor is, I'm not sure, as I don't know which quart you refer to. See http://en.wikipedia.org/w/index.php?title=Quart&oldid=290059902
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I need the n, dont know how to figure it out.
Simple algebra - solve the equation for n.
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sjb -
1 quarts (US, liquid) is equal to 0.95 liters
iDino -
does n mean the amount of the substance in moles?
what is the relationship between moles and mass?
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A major property of gasses is that they take up the volume of the container.
What you need to know is the bursting pressure of the ziplock bag. This pressure has to be higher than ATM pressure.
If you are trying to expand the bag with CO2 from the reaction. The pressure would have to be slightly higher than ATM pressure, or you would not see the bag expand.
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1 quarts (US, liquid) is equal to 0.95 liters
True, but 1 quart (UK, liquid) is equal to 1.137 litres, some 20% more, which I'm sure you can agree is significant, hence why I asked. I didn't see anything in the original post that disambiguated sufficiently for me as to which was needed.