Write the chemical equation showing dihydrogen phosphate and hydrogen phosphate conjugate acid-base relationship. Identify the acid and base. Explain how the equilibrium is shifted as buffer reacts with an acid and reacts with a base.

See above.

The conjugate acid-base relationship between dihydrogen phosphate (H2PO4-) and hydrogen phosphate (HPO42-) can be represented by the following chemical equation:

H2PO4- + H2O ⇌ HPO42- + H3O+

In this equation, dihydrogen phosphate (H2PO4-) acts as an acid, donating a proton (H+) to form its conjugate base, hydrogen phosphate (HPO42-). The hydronium ion (H3O+) is formed as a result of the water molecule accepting the proton.

Now, let's discuss how the equilibrium shifts when the buffer reacts with an acid or a base.

1. Reaction with an Acid:
When an acid is added to the buffer system, it increases the concentration of hydronium ions (H3O+). According to Le Chatelier's principle, to counteract the increased concentration of H3O+, the equilibrium will shift to the left to consume some of the hydronium ions. As a result, some of the hydrogen phosphate ions (HPO42-) will combine with the additional hydronium ions to form dihydrogen phosphate (H2PO4-). This reaction effectively neutralizes the added acid, maintaining the pH of the solution relatively constant. The buffer system helps to minimize changes in pH by acting as a reservoir of H3O+ and OH- ions.

2. Reaction with a Base:
If a base is added to the buffer system, the base will react with the hydronium ions (H3O+), decreasing their concentration. In response, according to Le Chatelier's principle, the equilibrium will shift to the right to replenish the H3O+ ions. This will result in the conversion of some hydrogen phosphate ions (HPO42-) to form additional hydronium ions (H3O+). Again, the buffer system helps to resist changes in pH by neutralizing the added base, ensuring that the solution remains relatively stable.

In summary, a buffer system consisting of dihydrogen phosphate and hydrogen phosphate can effectively resist changes in pH by reacting with added acids or bases. The equilibrium shifts to maintain a relatively constant concentration of hydronium ions and help maintain the pH of the solution.