A strong base is a substance that completely dissociates in water to produce hydroxide ions (OH-) and its conjugate acid. The conjugate acid of a strong base is the species that forms when the base accepts a proton (H+). For example, the conjugate acid of the strong base sodium hydroxide (NaOH) is water (H2O). This is because when NaOH dissolves in water, it completely dissociates into Na+ and OH- ions. The OH- ions can then react with water molecules to form H2O and hydroxide ions.

The strength of a conjugate acid is inversely related to the strength of its corresponding base. This means that the stronger the base, the weaker its conjugate acid, and vice versa. For example, the conjugate acid of the weak base ammonia (NH3) is the ammonium ion (NH4+), which is a relatively strong acid. This is because NH3 is only partially dissociated in water, so there are fewer NH4+ ions present in solution to react with hydroxide ions and form water.

In general, the conjugate acids of strong bases are not very acidic. However, there are some exceptions to this rule. For example, the conjugate acid of the strong base sodium hydride (NaH) is hydrogen gas (H2), which is a very strong acid. This is because NaH is a very strong base, so there are very few H- ions present in solution to react with hydroxide ions and form water.