1.

Explain the isothermal and free expansion of an ideal gas

Answer»

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SOLUTION :For ISOTHERMAL (T = CONSTANT) expansion of an ideal gas into vacuum, `w=0` since `p_(ex) = 0`. Also, Joule determined experimentally that `q=0`, THEREFORE, `Delta U=0`
`Delta U= q+w` can be expressed for isothermal irreversible and reversible changes as follows:
1. For isothermal irreversible change
`q=- w = p_(ex) (V_(f) - V_(i) )`
2. For isothermal reversible change
`q=-w = nRT "ln" (V_f)/( V_i) = -2.303 nRT log "" (V_f)/( V_i)`
3. For adiabatic change, `q=0`
`sigma Delta U= W_("ad")`


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