Competency #7
Answer and Explanation
The law of conservation of mass is always true for ordinary chemical reactions. So, if the reaction appears to lose mass, we must be losing a product somehow. In this case, notice that one of the products is hydrogen gas. As a gas, hydrogen does not stay in the container and so is not able to be included in the mass measurement. If you want to verify that mass was conserved, you could establish a system that would trap the hydrogen gas, measure its mass, and add it to the mass of the rest of the system.
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