How many moles of chlorine gas are in 1.2m^3 at room temperature and pressure?

What does a numerical subscript following an element in a chemical formula mean?

Which of these describes how heat is transferred by convection* a. sunlight travels through space without the aid of fluids or solids. b. warm air rises and takes the heat with it, eventually, it cools and sinks c. air at the equator rises and sinks at the poles. d. air molecules touch the warm ground, heating them up *not conduction

How many moles of na2s2o3 are needed to react with 0.12mol of cl2? show work.