According to the law of conservation of mass, why is it considered a mistake to add calcium to the product side if it is not in the reactant side of a particular chemical equation

Ab c or d ? i’m not sure what the answer is

Name 3 types of energy you see being used as you look around a classroom

The reaction below shows a system in equilibrium. how would a decrease in temperature affect this reaction? a. the rate of formation of the gases would increase. b. the equilibrium of the reaction would shift to the left. c. the equilibrium would shift to cause the gases to sublime into solids. d. the chemicals on the left would quickly form the chemical on the right.