When the potential energy is at its lowest point, attractive and repulsive forces are balanced, but the two atoms do not form a molecule. Why doesn't a stable bond form ?

Imagine that twenty i.u.’s of enzyme z were catalyzing the above reaction for one minute, under vmaxconditions, in a 3.00 ml assay volume. the assay is buffered with 20 mm phosphate buffer, ph 7.60. what will the ph be at the end of that one minute?