For an isothermal free expansion of an ideal gas,

Options

A. `Delta U = 0, q = 0, w = 0`
B. `Delta U != 0, q != 0, w = 0`
C. `Delta U != 0, q = 0, w = 0`
D. `Delta U = 0, q != 0, w = 0`

Answer

A

Explanation

Since internal energy of an ideal gas is directly proportional to its absolute temperature, `Delta U = 0`, for all isothermal processes involving and ideal gas, whether the processes is reversible of irreversible. For free expansion (i.e., expansion in vacuum), `w = 0` as `P_(ex)` is zero. According to first law `(Delta U = q + w), q` is also zero.