A 15.9-g sample of sodium carbonate is added to a solution of acetic acid weighing 20.0 g. The two substances react, releasing carbon dioxide gas to the atmosphere. After reaction, the contents of the reaction vessel weighs 29.3 g. What is the mass of carbon dioxide given off during the reaction?
Solution:
Using the law of conservation of mass, we can say the following.
The mass of the acetic acid + the sodium carbonate = contents of the reaction vessel + mass of carbon dioxide
Thus, we can write:
20.0 g + 15.9 g = 29.3 g +m_{CO_2}
m_{CO_2}=6.6g
This question can be found in General Chemistry, 9th edition, chapter 1, question 1.37