Calculate the number of moles of cl atoms in 1.81×10^24 formula units of magnesium chloride, mgcl2.

The answer for #3 is c but i don't know why

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

Compare and contrast physical changes with chemical changes.