Which of the following represents the atoms of 2 different elements?

Which substance absorbs 58.16 kj of energy when 3.11 mol vaporizes? a)ch4 b)h2s c)co2 d)nacl

18. use the activity series to predict whether the following synthesis reaction will occur. write the chemical equations for the reaction if it's predicted to occur. (s) + o2(g) -> *note: it is possible.*

Which type of precipitation would most likely form when the surface air temperature is slightly below freezing and the air temperature increases as you move upward away from the ground?