Pls help me I don’t understand it’s for my science class. Plz check if correct and tell me wether each is element or compound

Which best describes why nh4+ can form an ionic bond with ci-?

What is the mass of 4 molecules of co2

What is a main difference between a mixture and a pure substance? a mixture is only a liquid, but a pure substance can be in any state.a mixture looks the same throughout, but a pure substance does not.1 a mixture can vary in composition, but a pure substance has a set composlo a mixture can be made up of a single compound, but a pure substance car