Choose the words to finish the sentence. After learning about the law of conservation of mass, Sammy became interested in balancing equations. He knew that the symbol for aluminum was Al and silver tarnish was Ag2S. He also knew that mixing the two chemicals yielded pure silver, or Ag, in an aluminum sulfide solution. The equation showing this reaction is shown below.

3 Ag2S + 2 Al → 6 Ag + Al2S3

This equation is (blank) and it represents a (blank) chemical reaction.