Calculate the constant external pressure required to expand 2 moles of an ideal gas from volume 15 dm ⁻² to 20 dm ^2 if amount of work done is -600 ~J

Step-by-step solution

Work done during irreversible expansion against a constant external pressure is defined as W = -P_ ext V . Given values are W = -600 J , V₁ = 15 dm ^3 , and V₂ = 20 dm ^3 . The volume change is V = V₂ - V₁ = 5 dm ^3 . Since 1 J = 1 Pa m ^3 and 1 dm ^3 = 10⁻³ m ^3 , convert to SI units: V = 5 10⁻³ m ^3 . Substitute into the work formula: -600 = -P_ ext (5 10⁻³) . Solving for P_ ext gives P_ ext = 600 5 10⁻³ = 120000 Pa . Convert to bar using 1 bar = 10^5 Pa : P_ ext = 120000 10^5 = 1.2 bar . The final answer is A .