rxn gibbs free energy

[705121606]

How is the reaction gibbs free energy (calculated using delta g= -rtlnk = rtlnQ) different from the gibbs free energy we calculated last week?
And can someone explain why it would form products when positive and reactants when negative? Is it also spontaneous only if it is positive?

[Justin Sarquiz 2F]

When delta G is negative, the reaction is spontaneous, so it forms products because the reaction proceeds normally. When delta G is positive, the reaction is not spontaneous, so it forms reactants since the reaction does not proceed without an input of energy.

[Tai Metzger 3K]

When Q is greater than 1, delta G is positive and thus the rxn is not spontaneous in that direction. When Q is less than 1, delta G is negative and thus the rxn is spontaneous in that direction.

[Viviana Velasquez]

For a reaction to be spontaneous, delta G has to be negative. When delta G is negative, it means the forward reaction is favored and products are formed. When delta G is positive, the opposite happens and reactants are formed.

[Brianna Becerra 1B]

The delta G calculated last week is delta G naught or the change in Gibb's Free Energy under standard conditions. We were first taught to calculate this using Delta H naught - T x Delta S naught. This week, we learned how to calculate the same change in Gibbs Free Energy under standard conditions through Delta G naught = - RTlnK. We also learned how to calculate the change in Gibbs free energy through: Delta G = Delta G naught + RTlnQ. It is important to note that delta G and delta G naught are different causing their calculations to vary as well.

[Brandon Valafar]

Delta G has to be negative for a reaction to be spontaneous. Therefore, when delta G is negative, it means products are formed. When delta G is positive the reaction is not spontaneous and reactants are formed.