Question

A sample of He gas kept in an inflatable balloon with a volume of 1.50 L and at a temperature of 27.0 ^oC exerted a pressure of 4.50 atm. What is the number of moles of He gas present? 

Answer 1

$PV$ $=nRT$

$4.5×1.5=n×0.08206×(273+27)$

$n=0.2742\>moles$