7. What rule of thumb is useful for predicting whether one substance will
dissolve in another?

Ch4 and ph3 are both covalent since they are composed both of non-metals.    ch4 is non- polar because of  london forces and has a geometry of tetrahedral  ph3 , on the other hand, is umbrella shaped polar and has dipole-dipole intermolecular force (imf) . since ph3 is polar, it has a stronger imf   

Answer it is also known as the completion state is untrue of the activation complex;

Putting salt in vinegar water