A sample of neon effuses from a container in 76 seconds. the same amount of an unknown noble gas requires 155 seconds. part a identify the gas.

The rate of gas effusion or diffusion is inversely proportional to the square root of molar mass

molar mass of neon is 20

let the molar mass of unknown gas be y

155/76=sqrs of y/20

square both side to remove the square root sign

155^2/76^2 = y/20

by cross multiplication y={ (24025 x 20) / 5776}=83.18

the gas is krypton since 83 is one isotope of krypton