Final answer:
Ba(OH)2 is classified as a strong base because it dissociates completely in water, releasing hydroxide ions, which is characteristic of hydroxides from heavier alkaline earth metals.
Step-by-step explanation:
Ba(OH)2 is a substance that when dissolved in water, yields hydroxide ions, OH-. It is an ionic compound composed of the alkaline earth metal cation barium (Ba2+) and the hydroxide ion. According to the provided excerpts, strong bases are those that dissociate completely in water, which includes the hydroxides of alkali metals and the heavier alkaline earth metals like calcium, strontium, and barium. Therefore, Ba(OH)2 is a strong base, which falls under option 3) when classifying the compound as a strong acid, weak acid, strong base, weak base, or non-electrolyte.