What defines a strong base in chemistry?

A strong base is defined by its ability to completely dissociate in water, resulting in a high concentration of hydroxide ions (OH⁻). This characteristic is essential for distinguishing strong bases from weak bases, which do not fully dissociate. When a strong base dissolves in water, it yields a solution with a significant increase in pH, usually above 12, indicating a highly basic environment.

The complete dissociation in water also implies that strong bases can effectively neutralize acids, which is why they tend to react vigorously, but this is a result of their strong nature, not the defining feature. The pH value of a strong base is high, not low as presented in another option. Therefore, while strong bases can produce gases when reacting with certain substances, that is not a general definitional trait of all strong bases.

Overall, the defining feature of a strong base is its ability to completely dissociate in an aqueous solution, allowing it to exert its basic properties effectively.