The Law of Conservation of Mass states that mass changes before and after a change. True

False

Noble gases are the most reactive elements on the periodic table. a. true b. false

For which one of the following reactions is the value of δh° rxn equal to δh° f for the product? a. 2 h2 (g) + o2 (g) → 2 h2o (l) b. n2 (g) + o2 (g) → 2 no (g) c. 2 h2 (g) + o2 (g) → 2 h2o (g) d. h2o (l) + 1/2 o2 (g) → h2o2 (l) e. none of the above

The formation of a solid, also known as a is an indication of a chemical change. precipitate particulate particle powder