Question

The spontaneity of a standard reaction, ΔG^o, depends on both ΔH^o and ΔS^o. Given the following reaction and data table, decide which of the statements shown below are true.
Assume that ΔH^o and ΔS^o are independent of Temperature.

3 O₂ (g) → 2 O₃ (g)

ΔHorxn	285 kJ
ΔSorxn	-137 J/K

You will get credit when you answer correctly.

Select all that are True.
This reaction is endothermic
This reaction is exothermic
This reaction is endergonic (ΔG^o > 0) at 298 K
This reaction is exergonic (ΔG^o < 0) at 298 K
This standard reaction will only be spontaneous at high temperatures (T > 2080 K)
This standard reaction will only be spontaneous at low temperatures (T < 2080 K)
This standard reaction will be spontaneous at all temperatures
This standard reaction will not be spontaneous at any temperature

Answer 1

The True statements are :-

• This reaction is endothermic
• This reaction is endergonic (G^o > 0) at 298 K
• This standard reaction will not be spontaneous at any temperature

Explanation

Since H^o_rxn is positive, therefore reaction is endothermic

G^o = H^o_rxn - T * S^o_rxn

S^o_rxn is negative and Temperature will always be positive, therefore the term (- T * S^o_rxn) will always be positive

This means G^o will always be positive as H^o_rxn is positive and the term (- T * S^o_rxn) is also positive