a what is any substance that can accept a hydrogen ion
the arrhenius definition of a base is a species that tends to donate hydroxide ions or accept hydrogen ions in solution on the other hand an arrhenius acid tends to donate hydrogen ions or accept hydroxide ions therefore as you guessed when hydrogen ion concentration decreases ph increases the h3o ion is called a hydronium ion and this alternate definition of ph is equivalent to the first to see why consider what actually happens when an arrhenius acid dissociates in an aqueous water containing solution ha h2o a h3o in this reaction ha is the acid and a is its conjugate base