9.

Which is true of hydroxide ions?

They are not found in pure water.

They have a negative charge.

They dissociate to form protons.

They contain two hydrogen atoms.

They have a negative charge.

Explanation:

Acids may be defined as the substance that has hydrogen ions whereas the base has the ability to produce hydroxide ions. Both the hydrogen and hydroxyl ions carry charge over them.

Hydroxide ions carry negative charge over them. Hydroxide ions are present in bases as well as in the water molecule. Hydroxide ions can not be dissociated to form the protons. A single hydrogen atom is present in hydroxide ions.

Thus, the correct answer is option (2).