1. Here is an experiment to show that a lighter gas diffuses faster than a heavier one.
Take two balloons. Fill one with helium gas and the other with air. Now let the helium balloon deflate. Record the time for complete deflation. Then deflate the balloon with air. Note the deflation time.
You will find that the time to deflate helium balloon is way less than the time to deflate air balloon.
2. Hydrogen will diffuse faster and by a factor of 3.
Explanation: Deflation time depends on the velocity of a gas and the Graham's law of diffusion gives the relation square root ( m1 /m 2) = v 2 /v1 where 1 is heavy gas and 2 is lighter gas.