6.4 * 6.02 * 10^23 = 3.8528*10^24 atoms
Don't let the fact that it's vanadium throw you off, avagadros constant stays the same for all elements
Can you take picture of the whole question? I can’t see.
Answer:
I believe it's
4-floro-5,6,8-Tribromo-3,3,7-trimethylnonane
The helium would expand into the air of the room. Depending on how big the room is, and the amount of helium in the jar, it could cause damage to health. The only way this would happen is if the room was small and the jar was big.
I hope this helps!