I was confused by why the following elimination reaction hits only one of the hydrogens instead of both isomers that are possible. Please help me out!
Conjugated dienes are significantly favorable to non-conjugated dienes (because of delocalization and hybridization, etc.), so this will be the major product. It is not to say that the other reaction cannot happen, but that a combination of factors leads to that product being major. All of chemistry occurs in an equilibrium of some degree, and the reaction above will become most stable in conjugated diene form.