I am taking a chemistry course and am struggling with thermodynamics problems.

Assuming Potassium feldspars (K feldspars) and kaolinite minerals can coexist and react.

Calculate the Delta G for the following the following reaction at a solution pH of 5.0.

K-feldspar + 2H+ = Kaolinite + 4 H4SiO4° + 2K+ K = 10-5.0

Which product (feldspar or kaolinite) will spontaneously form? Assume (K+) = 10-3; (H4SiO4o) =10-5; (H+) = 10-5; Temperature = 298° K.

My main question is how to find H+. I know to get H+ I have to take the antilog times (pH), but which factor in the equation is the unknown Delta G. Thanks for the help. I realize this could be a stupid question but I am taking a 400 level chemistry course and have not taken a chem class in a few years.