If a sample of helium gas is at 0.5 atm, 25 liters, and 300 K, how many moles of gas do I have? *

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