[Halmarsta]

I have 3.0 M HCl and baking soda, NaHCO₃. How can I use only these two things to get carbon dioxide in a bag? The best thing I can think of is putting a beaker of HCl in the bag and the baking soda outside the beaker, but still in the bag, then sealing the bag and flipping the bag over to get it to react. However, then we have CO₂ and other byproducts in the bag. How can I only get CO₂ in there?

Thanks!

[Burner]

CO₂ should be the only gaseous product in this reaction. The common procedure to collect it is by downwards delivery

https://www.google.com.hk/search?espv=2&biw=1920&bih=955&tbm=isch&sa=1&q=downwards+delivery&oq=downwards+delivery&gs_l=img.12...0.0.0.936.0.0.0.0.0.0.0.0..0.0....0...1c..64.img..0.0.0.I6OEYaqO4dk

[Arkcon]

Like Burner: said, you haven't told us your real limitations, just the implied ones that you can't have other equipment.  However, the plastic bag was mentioned, but not the beaker.  So if you can have a beaker, then a flask, stopper, hose . drying tube, evacuation pump ... transfer pump, ... liquid helium dewar ... haven't been taken off the table.