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I experimented CO2 generation by adding 4 g of 25% acetic acid water solution (=1g of acetic acid) to 1.4g of pure baking soda. But this mixture yielded only 50% less than the calculated amount 373 mL of CO2.

CH3COOH = 60g/mol, NaHCO3 = 84g/mol --> CH3COOH 1g : NaHCO3 1.4g. CH3COOH + NaHCO3 --> CH3COONa + H2O + CO2 mol to mol = 1 mol of CO2. CO2 = 44g/mol. --> CO2 0.733g : CH3COOH 1g : NaHCO3 1.4g Gas = 22.4L per mol --> 22.4L/60 = 373.3 mL (= 0.733g) = THEORETICAL YIELD. ACTUAL YIELD = 190 mL by volume measurement. (only 50%) ACTUAL YIELD = 0.586g (=298.6 mL) by mass measurement. (only 80%)

I set the water filled measuring cup upside down above the water filled plate, and attached hose underneath the skirt of the cup so that any gas generated from the sealed bottle of the mixture to get provided into the measuring cup.

Moreover, I checked the amount of CO2 yielded by the weight loss method. That is, I measured the mixture above the scale to see how much CO2 is evaporated during the chemical reaction.

The above 2nd method provided me with 80% yield.

50% of air volume and 80% of mass are coming with the consistency during the several times of experiments.

What was wrong with my experiment??

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I'm assuming your calculations and materials are correct here. Acetic acid is a weak acid and as such will for a buffer solution with a weak base. So at half your reaction completion you will have generated a sodium acetate buffer with pH ~5. At this stage the acidity of your solution might not be enough to protonate all the carbonate.

Try to add a stronger acid if you can.

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  • $\begingroup$ Oh, I missed one thing. I already tried 4g of acetic acid + 1.4g of sodium bicarbonate only to have just around 50% yield. In this case, acidity is already high enough and still keeps high even after reacting with 1.4g of sodium bicarbonate, but why the yield doesn't get higher?? $\endgroup$ – user58029 Sep 11 '18 at 7:44
  • $\begingroup$ How did you test for acidity? What pH did you have? $\endgroup$ – Chris Sep 11 '18 at 7:53
  • $\begingroup$ I didn't. I added 100% acetic acid solution bought from lab material shopping mall to the tap water. Tests were done in order of #1 1 g acetic acid without water, #2 1g acetic + 3g water, #3 2g acetic + 3g water, #4 3g acetic + 3g water, #5 4g acetic + 3g water, #6 2g acetic without water, #7 3g acetic without water, with fixed amount of Arm & Hammer backing soda which is 1.4g. $\endgroup$ – user58029 Sep 11 '18 at 8:10
  • $\begingroup$ You can try different amounts of baking soda to make sure it is actually pure bicarbonate. $\endgroup$ – Chris Sep 11 '18 at 8:19
  • $\begingroup$ Watch this guy. youtube.com/watch?v=5pPPFI8E33U . He also has consistant 45% percent yields. $\endgroup$ – user58029 Sep 11 '18 at 8:49

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