Yes I have come across this, but didn't realize the exact difference. Thank you for the clarification :Dmjc123 said:ΔG° is the value of ΔG with all reagents in their standard states. You ought to have encountered this definition in your study of thermodynamics.
For example, if ΔG is the free energy change for a reaction in a system described by the reaction quotient Q (have you come across this?), then
ΔG = ΔG° + RTlnQ
At equilibrium Q = Keq and ΔG = 0, so
ΔG° + RTlnKeq = 0
G and G(o) refer to different values of the gravitational constant, also known as the universal gravitational constant or Big G. G is the average value of the gravitational constant, which is used in most calculations, while G(o) is the theoretical value of the gravitational constant at the center of the Earth.
The value of G varies depending on the location and density of the object being measured. G(o) represents the theoretical value at the center of the Earth, where the majority of the Earth's mass is concentrated. G, on the other hand, is an average value that takes into account the varying densities of different objects in the universe.
G and G(o) are related through the mass and density of the Earth. G(o) is calculated using the average density of the Earth, while G is calculated using the overall mass of the Earth. G(o) is approximately 0.3% larger than G due to the inverse relationship between mass and density in the gravitational constant equation.
G is the value of the gravitational constant used in most calculations, as it takes into account the varying densities of objects in the universe. G(o) is more of a theoretical value that is used in specific calculations relating to the Earth's gravitational field.
G(o) was determined through experiments and measurements of the Earth's gravitational field. By measuring the acceleration due to gravity at the Earth's surface and knowing the Earth's mass and radius, scientists were able to calculate the theoretical value of the gravitational constant at the center of the Earth.