Help i suck at chemistry The natural abundance for boron isotopes is 19.9% 10B and 80.1% 11B . Calculate boron’s atomic mass.

Alidded glass container is filled with a colored gas. after a period of time, it is observed that the gas is uniformly spread throughout the box and that the movement has slowed considerably. next, a warm iron plate is carefully placed under the box. why is there resumed movement of the gas in the container?