[sinthreck]

The point on the curve that indicates the composition of the reaction mixture at equilibrium is (see attachment).

I thought the answer was C, because delta G = 0 but that's not the answer provided in the textbook.

Please give me a hint

[majorjp]

That graph is a bit different from the representation I'm use to but it seem like it has its basis in G and ξ. Using Gibbs Free Energy, equilibrium is defined as the point that (dG/dξ)=0. This means that the derivative of Gibbs free energy equals the derivative of the extent of reaction. Graphically this point is best described in your example as the point where the tangent to the curve has a slope of 0. That point is one of the choices.

[sinthreck]

very good -thank you.