Phosphoric acid is a tribasic acid because it has three ionizable hydrogen atoms in its structure. This means that it can donate three protons in water to form three H+ ions.

Phosphoric acid, also known as orthophosphoric acid (H3PO4), is a mineral acid commonly used in various industries such as food and beverage, fertilizers, and detergents. It is a colorless liquid with a strong odor.

The structure of phosphoric acid consists of three hydroxyl groups (-OH) attached to a central phosphorus atom (P). Each of these hydroxyl groups can dissociate to release one proton (H+), resulting in the formation of three negatively charged phosphate ions (PO43-). This acid can be represented by the following equation:

H3PO4 ⇌ H+ + H2PO4- (first dissociation)
H2PO4- ⇌ H+ + HPO42- (second dissociation)
HPO42- ⇌ H+ + PO43- (third dissociation)

- Hydrochloric acid:
Hydrochloric acid (HCl) is a monobasic acid because it has only one ionizable hydrogen atom. It can dissociate in water to form one H+ ion. The dissociation equation for hydrochloric acid is as follows:
HCl ⇌ H+ + Cl-

- Nitric acid:
Nitric acid (HNO3) is also a monobasic acid because it has one ionizable hydrogen atom. It can dissociate in water to form one H+ ion. The dissociation equation for nitric acid is as follows:
HNO3 ⇌ H+ + NO3-

- Sulphuric acid:
Sulphuric acid (H2SO4) is a dibasic acid because it has two ionizable hydrogen atoms. It can dissociate in water to form two H+ ions. The dissociation equation for sulphuric acid is as follows:
H2SO4 ⇌ 2H+ + SO42-

In summary, phosphoric acid is a tribasic acid because it can donate three protons in water, while hydrochloric acid, nitric acid, and sulphuric acid are monobasic and dibasic acids respectively.