According to the law of conservation of mass, Billy should have 12 grams after the experiment is finished.
Billy starts with 12 grams of sodium hydroxide as part of an experiment.
According to the law of conservation of mass, matter is not created not destroyed over the course of physical or chemical changes.
Thus, if he starts with 12 grams before the experiment, he must end with 12 grams after the experiment.
According to the law of conservation of mass, Billy should have 12 grams after the experiment is finished.
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