Monday 24 August 2015

aqueous solution - vinegar + baking soda = yields far smaller volume of CO2 gas than calculation


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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