Why would 18 be wrong for the atomic mass of an atom with 6 neutrons, 6 electrons, 6 protons?

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.