What's CO2 please explain in detail

Which of the following is not a good technique for managing used oil? a) have specific, labeled catch pans available for technicians who are collecting oil b) spills in your shop and any releases on pavement or outside should be poured down a drain c) do not use oil containers for antifreeze or other non-similar fluids d) be prepared for oil spills with the proper absorbents

Write the empirical chemical formula of calcium with a mass percent of 38.8, phosphorus with a mass percent of 20.0, and oxygen with a mass percent of 41.3.

What is the mass of 0.46 mol of mgcl2