Which of the following would have the slowest rate of diffusion at a given temperature

o2
ne
cl2
he

Chlorine will have the slowest rate of diffusion because it has the highest   relative molecular mass of 71 followed by O₂ with 32, then Neon 20 then He with 2

The rate of diffusion of a gas is inversely proportional to the square root of its relative molecular mass.  

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.

so she was walking and she stepped on warm jeffy , uh uh uhh dadye i just pooped my pants