What is the mass of an empty film canister?

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.

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

What is the number of neutrons in an atom with atomic mass of 35