Select the most appropriate option. A gas is allowed to expand in a well-insulated container against a constant external pressure of 2.5 bar from an initial volume of 2.5 L to a final volume of 4.5 L. The change in internal energy, ΔU of the gas will be _______.

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KollegeApply · Accepted Answer

- 500 J Explanation: Since the container is insulated, this is an adiabatic process. For adiabatic process, ΔU = +W = - Pext Δ V = - Pext (V2 - V1) Initial volume (V1) = 2.5 L = 2.5 dm3 Final volume (V2) = 4.5 L = 4.5 dm3 External pressure (Pext) = 2.5 bar ΔU = W = - 2.5 bar $\times$ (4.5 dm3 - 2.5 dm3) = - 5.0 dm3 bar $\times$ (100 "J")/(1 "dm"^3 "bar") = - 500 J

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