Simulation · Chemistry · Class 11
Same start, same end, different work
From the lesson Pressure-volume work in Thermodynamics. Change the values and watch what happens.
Same start, same end, different workChemistry · Class 11
The idea behind it
NCERT § "Applications"
- For expansion or compression against a constant external pressure, w = −pₑₓ(V_f − V_i) = −pₑₓΔV.
- In expansion ΔV is positive, so w is negative (the system does work); in compression ΔV is negative, so w is positive.
- A reversible process proceeds through a series of equilibrium states, with the external pressure differing from the internal pressure only infinitesimally at every step.
- Reversible isothermal expansion of an ideal gas: w_rev = −2.303 nRT log(V_f/V_i).
- Reversible expansion does more work on the surroundings than an irreversible expansion between the same two states.
- Free expansion is expansion into a vacuum (pₑₓ = 0), so no work is done; for an ideal gas ΔU is also zero because it has no intermolecular attractions.
- For isothermal changes of an ideal gas ΔU = 0, so q = −w: irreversible q = pₑₓ(V_f − V_i), reversible q = 2.303 nRT log(V_f/V_i), free expansion q = 0.
- Work of 1 L bar equals 100 J.