An unknown mass of Helium gas undergoes an isothermal reversible expansion at 300 K from an initial volume of 2 L to a final volume of 20 L . If the magnitude of work done by the gas is 11454 J , the mass of Helium gas is _________ g . (Given: Molar mass of He = 4 g mol ⁻¹ , R = 8.3 J K ⁻¹ mol ⁻¹ , (10) = 2.3 )

Step-by-step solution

For an isothermal reversible expansion, the magnitude of work done is given by: |W| = nRT ( V₂ V₁ ) Given: |W| = 11454 J T = 300 K V₁ = 2 L V₂ = 20 L R = 8.3 J K ⁻¹ mol ⁻¹ (10) = 2.3 Substituting the values: 11454 = n 8.3 300 ( 20 2 ) 11454 = n 2490 (10) 11454 = n 2490 2.3 11454 = n 5727 n = 11454 5727 = 2 moles The mass of Helium gas is: Mass = n Molar mass = 2 4 = 8 g Answer: 8