Work done by the system in isothermal reversible process is `w_(rev.)= -2.303 nRT "log"(V_(2))/(V_(1))`. Also in case of adiabatic reversible process work done by the system is given by: `w_(rev.) = (nR)/(gamma -1) [T_2 - T_1]`. During expansion disorder increases and the increase in disorder is expressed in terms of change in entropy `DeltaS = q_(rev.)/T`. The entropy changes also occurs during transformation of one state to other end expressed as `DeltaS = DeltaH/T`. Both entropy and enthalpy changes obtained for a process were taken as a measure of spontaniety of process but finally it was recommended that decrease in free energy is responsible for spontaniety and `DeltaG=DeltaH - T DeltaS`.
A chemical change will definitely be spontaneous if:

Options

A. `DeltaH=-ve, DeltaS=-ve` and low temperature
B. `DeltaH=+ve, DeltaS=-ve` and high temperature
C. `DeltaH=-ve, DeltaS=+ve` and any temperature
D. `DeltaH=+ve,DeltaS=+ve` and `TDeltaS lt DeltaH`

Answer

c

Explanation

`DeltaG=DeltaH-TDeltaS`
`=-ve-Txx(+ve)=-ve`