What is conjugate acid of oh-?

The conjugate acid of OH- is H2O, also known as water.

When OH- (hydroxide ion) gains a hydrogen ion (H+), it forms water (H2O). This can be represented by the chemical equation:

OH- + H+ --> H2O

In this reaction, OH- acts as a base by accepting a proton (H+) to form water. The resulting species, H2O, is the conjugate acid of hydroxide ion. It is important to note that water itself can act as both an acid (by donating a proton) and a base (by accepting a proton), making it amphoteric.