Equation based on equilibrium

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

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

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

305174946
Posts: 61
Joined: Fri Sep 28, 2018 12:17 am

Equation based on equilibrium

Can someone please explain the G=G+RTlnQ equation please. Lavelle wrote Q is reaction quotient not K, is he just emphasizing that its not at equilibrium? I thought it was....?

Samantha Kwock 1D
Posts: 61
Joined: Fri Sep 28, 2018 12:24 am

Re: Equation based on equilibrium

The G= G + RTlnQ equation holds true for all reactions, even reactions not at equilibrium. However, for reactions at equilibrium, G=0 and Q=K so G=-RTlnK.

michelle
Posts: 62
Joined: Fri Sep 28, 2018 12:23 am

Re: Equation based on equilibrium

Actually, it should be G=G knot + RTlnQ. It implies that the reaction is not at equilibrium.

EllaBerry
Posts: 68
Joined: Fri Sep 28, 2018 12:29 am

Re: Equation based on equilibrium

You would use the equation with the K when the reaction is at equilibrium. Meanwhile, use the equation with the Q at any time.

katie_sutton1B
Posts: 61
Joined: Fri Sep 28, 2018 12:17 am

Re: Equation based on equilibrium

K indicates equilibrium, so you would use that equation for a reaction at equilibrium. You would use Q when it not.

KHuang1L
Posts: 60
Joined: Fri Sep 28, 2018 12:19 am

Re: Equation based on equilibrium

Delta G = Delta G under standard conditions + RTlnQ is used when the reaction is not at equilibrium. When the reaction is at equilibrium, you use the equation delta G under standard conditions = -RTlnK because delta G is equal to zero and the equilibrium constant can be used.