Which of the following is correct?

Options

A. Reversible adiabatic process is isoentropic
B. `Delta S_("sys')` for irreversible adiabatic compression is greater than zero
C. `Delta S_("sys")` for free expansion is zero
D. `Delta S_("sys')` for irreversible isothermal compression is greater than zero

Answer

A, B

Explanation

Reversible adiabatic `rArr q_("rev") = 0 rArr Delta S = 0`
For irreversible, `Delta S lt 0` for compression and `Delta S gt 0` for expansion
For free expansion, `P_("ext") = 0` but `Delta S gt 0`
Irreversible isothermal `rArr Delta S = nR "ln" (V_(2))/(V_(1))`
Compression `rArr V_(2) lt V_(1) rArr Delta S lt 0`