Answer is: 9,7 L is needed to store helium gas. n(He) = 0,80 mol. p(He) = 204,6 kPa. T = 300 K. R = 8,314 J/K·mol; universal gas constant. Use ideal law eqaution: p·V = n·R·T. V = n·R·T / p. V(He) = 0,80 mol · 8,314 J/K·mol · 300 K ÷ 204,6 kPa. V(He) = 9,75 L.