## Finding standard reaction for a reaction

$\Delta G^{\circ}= \Delta H^{\circ} - T \Delta S^{\circ}$

$\Delta G^{\circ}= -RT\ln K$

$\Delta G^{\circ}= \sum \Delta G_{f}^{\circ}(products) - \sum \Delta G_{f}^{\circ}(reactants)$

Jose Torres
Posts: 31
Joined: Fri Sep 28, 2018 12:22 am

### Finding standard reaction for a reaction

Given the reaction $2H_{2}O_{2}(l)\rightarrow 2H_{2}O(l)+O_{2}(g)$ , when trying to find standard reaction of entropy, enthalpy, and Gibbs Free Energy, why is $O_{2}$ used in finding the standard reaction of entropy but not of enthalpy and Gibbs Free Energy? Is it just because it's a gas?

Meachelle_Lum_1I
Posts: 92
Joined: Fri Sep 28, 2018 12:24 am

### Re: Finding standard reaction for a reaction

Oxygen is still used in all three formulas. For enthalpy, the formation reaction is the deltaH of the entire reaction. In the textbook, Hrxn is already given of H20, with Oxygen taken in to account. And for Gibbs Free Energy, since the formula is G=H-TS, if entropy and enthalpy use O2, so will Gibbs.

Laura Gong 3H
Posts: 89
Joined: Fri Sep 28, 2018 12:26 am
Been upvoted: 1 time

### Re: Finding standard reaction for a reaction

O2 is probably not included in the calculations for delta H and delta G because standard enthalpy of formation of O2 and the free energy of O2 are both 0.

Kevin ODonnell 2B
Posts: 62
Joined: Fri Sep 28, 2018 12:24 am

### Re: Finding standard reaction for a reaction

The only reason I can think of is because O2 is already in its most standard state so this would be counted as 0 for those calculations. The textbook goes more into detail on which calculation to use standard state of elements = 0 for.