Under isothermal and reversible conditions,the term "free energy" in thermodynamics signifies

For a certain reaction,$\Delta H = -225 \ kJ \ mol^{-1}$ and $\Delta S = -150 \ J \ K^{-1} \ mol^{-1}$. Find the temperature at which $\Delta G$ is zero. (in $K$)

For a reaction $\Delta H = -30 \ kJ$ and $\Delta S = -45 \ J \ K^{-1}$,at what temperature does the reaction change from spontaneous to non-spontaneous (in $K$)?

For the oxidation of ammonia at $298 \ K$,the standard enthalpy and standard entropy changes are $-382.64 \ kJ \ mol^{-1}$ and $-145.6 \ J \ K^{-1} \ mol^{-1}$ respectively. The standard Gibbs energy change for the same reaction at $298 \ K$ is $..... \ kJ \ mol^{-1}$.

The spontaneous nature of a reaction is impossible if

The standard enthalpy for the decomposition of $N_2O_5$ to $NO_2$ is $58.04 \ kJ$ and standard entropy of this reaction is $176.7 \ J/K$. The standard free energy change for this reaction at $25 \ ^oC$ is .................. $kJ$.