How many molecules of he are contained in a 10.0 l tank at 7.53 atm and 485 k?

1.126 x 10^22

Explanation:

pV = nRT

7.53 x 10 = n x 8.31 x 485

n = (7.53 x 10) / (8.31 x 485) = 0.0187 moles

M = n x Avogadros number

0.0187 x 6.02 x 10^23 = 1.126 x 10^22