The combination of plots which does not represent isothermal expansion of an ideal gas is –

For diatomic ideal gas in a closed system, which of the following plots does not correctly describe the relation between various thermodynamic quantities?

For the equilibrium,
2H₂O $$\rightleftharpoons$$ H₃O⁺ + OH^$$-$$, the value of $$\Delta $$G^o at 298 K is approximately :

The reaction, MgO(s) + C(s) $$ \to $$ Mg(s) + CO(g), for which $$\Delta $$_rH^o + 491.1 kJ mol^–1 and $$\Delta $$_rS^o = 198.0 JK^–1 mol^–1, is not feasible at 298 K. Temperature above which reaciton will be feasible is :