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.
The chemical equation showing the dihydrogen phosphate and hydrogen phosphate conjugate acid-base relationship is:
H2PO4- (dihydrogen phosphate) + H2O ⇌ H3O+ (hydronium ion) + HPO42- (hydrogen phosphate)
In this equation, the dihydrogen phosphate (H2PO4-) acts as an acid by donating one of its protons (H+) to water (H2O), forming the hydronium ion (H3O+). Simultaneously, the dihydrogen phosphate donates a hydrogen ion to make it a hydrogen phosphate ion (HPO42-), which acts as the base.
Now, let's discuss how the equilibrium is shifted as a buffer reacts with an acid and with a base.
When a buffer reacts with an acid:
In the presence of an acid, the buffer's weak acid component (such as dihydrogen phosphate) reacts with the additional H+ ions from the acid. This reaction consumes the added H+ ions, shifting the equilibrium towards the left in the equation mentioned above. As a result, there will be a decrease in the concentration of H3O+ (hydronium ions) and an increase in the concentration of H2PO4- (dihydrogen phosphate), resisting any significant change in the pH of the solution.
When a buffer reacts with a base:
In the presence of a base, the buffer's weak base component (such as hydrogen phosphate) reacts with the OH- ions from the base. This reaction consumes the OH- ions, shifting the equilibrium towards the right in the given equation. As a result, there will be an increase in the concentration of H3O+ (hydronium ions) and a decrease in the concentration of HPO42- (hydrogen phosphate), preventing any substantial change in the pH of the solution.
In summary, a buffer helps to resist changes in pH by utilizing the conjugate acid-base relationship to neutralize additional H+ ions or OH- ions introduced by an acid or a base, respectively. This equilibrium shifting mechanism ensures that the pH of the solution remains relatively stable.
The dihydrogen phosphate and hydrogen phosphate species are related by a conjugate acid-base relationship. The chemical equation representing this relationship is as follows:
H2PO4^- + H2O ⇌ H3O+ + HPO4^2-
In this equation:
- The dihydrogen phosphate (H2PO4^-) acts as the acid because it donates a proton (H+) to water.
- Water (H2O) acts as the base and accepts a proton to form hydronium ion (H3O+).
- The resulting species, hydrogen phosphate (HPO4^2-), has accepted a proton and acts as the base in this equilibrium.
Now, let's discuss how the equilibrium is shifted when the buffer reacts with an acid or a base.
When the buffer reacts with an acid:
- If an acid is added to the buffer, it will increase the concentration of hydronium ion (H3O+).
- According to Le Chatelier's principle, the equilibrium will shift to the left to relieve the excess hydronium ion concentration.
- This shift occurs by some of the hydronium ions reacting with the hydrogen phosphate (HPO4^2-) ions to form dihydrogen phosphate (H2PO4^-), consuming the excess H3O+ in the process.
When the buffer reacts with a base:
- If a base is added to the buffer, it will increase the concentration of hydroxide ion (OH-).
- According to Le Chatelier's principle, the equilibrium will shift to the right to consume the excess hydroxide ion concentration.
- This shift occurs by the hydroxide ions reacting with the dihydrogen phosphate (H2PO4^-) ions to form hydrogen phosphate (HPO4^2-), consuming the excess OH- in the process.
In both cases, the equilibrium of the conjugate acid-base relationship in the buffer system helps maintain the pH within a certain range as it resists changes in its acidity or basicity. This ability is what makes the buffer system important for maintaining stable conditions in biological and chemical processes.