lecture 3

# lecture 3 - reversible paths • a reversible path is an...

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examples and reversible processes EXAMPLE: Consider the isothermal expansion of an ideal gas into a vacuum. Calculate Δ U, Δ H, q and w for this expansion. Suggest an isothermal process for returning the gas to its initial volume. EXAMPLE: Consider the isothermal expansion of V i = 10 l of an ideal gas at P i = 4 atm to V f = 40 l, P f = 1 atm, and then compression back to the initial state. Calculate q and w for the following paths: handout 5 P ext is kept constant at 1 atm for the expansion, and at 4 atm for the compression handout 6 in three steps handout 7 in six steps handout 8 in a very large number of steps such that P ext is kept inFnitessimally close to P through- out the process. handout 8a

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Unformatted text preview: reversible paths • a reversible path is an equilibrium path 1 • The values of P and T can change, but through-out T = T ext and P = P ext • The system does maximum work on the sur-roundings, and the heat transferred to the sys-tem is maximum, i.e. (-w ) max =-w equil path =-w rev ≥ -w q max = q equil path = q rev ≥ q EXAMPLE: Consider one mole of a monatomic ideal gas contained in a rigid vessel having a vol-ume of one litre at T = 300 K. The gas is heated at constant volume to 400 K. Calculate q, w, Δ E and Δ H for this process. Why isn’t q = Δ H ? (Ans: 1247J, 0, 1247J, 2079J) 2...
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lecture 3 - reversible paths • a reversible path is an...

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