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💏intro to chemistry review

H2PO4-

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

H2PO4- is the dihydrogen phosphate ion, a polyatomic ion with a charge of negative one. It is a key component in the chemical equilibrium of polyprotic acids, which are acids that can donate more than one proton.

5 Must Know Facts For Your Next Test

  1. The H2PO4- ion is the predominant conjugate base species of phosphoric acid (H3PO4) at pH values between 2 and 7.
  2. H2PO4- can accept a proton to form the H3PO4 species or lose a proton to form the HPO4(2-) species, depending on the pH of the solution.
  3. The presence of H2PO4- in a solution helps to maintain a relatively stable pH, making it an important component of biological buffer systems.
  4. H2PO4- is involved in the regulation of the body's acid-base balance and plays a crucial role in cellular energy production through its involvement in the phosphate cycle.
  5. The H2PO4- ion is also an important component in fertilizers, where it provides phosphorus, a essential nutrient for plant growth and development.

Review Questions

  • Explain the role of H2PO4- in the chemical equilibrium of polyprotic acids.
    • The H2PO4- ion is the predominant conjugate base species of the polyprotic acid, phosphoric acid (H3PO4), in the pH range of 2 to 7. It is formed when phosphoric acid loses its first proton. The H2PO4- ion can then accept or donate a proton, depending on the pH of the solution, to maintain a relatively stable pH. This ability to participate in proton transfer reactions makes H2PO4- an important component in the chemical equilibrium of polyprotic acids.
  • Describe the importance of H2PO4- in biological systems and its involvement in cellular processes.
    • In biological systems, H2PO4- plays a crucial role in the regulation of the body's acid-base balance. It is an important component of biological buffer systems, helping to maintain a stable pH in the body. Additionally, H2PO4- is involved in the phosphate cycle, which is essential for cellular energy production through processes like ATP synthesis. The presence of H2PO4- in cellular environments allows for the efficient transfer of phosphate groups, which is necessary for various metabolic reactions and signaling pathways.
  • Analyze the significance of H2PO4- in the context of its applications, such as in the production of fertilizers.
    • Beyond its importance in biological systems, H2PO4- is also a valuable component in the production of fertilizers. As a source of phosphorus, a essential nutrient for plant growth and development, H2PO4- is added to fertilizers to promote healthy plant growth and yield. The ability of H2PO4- to participate in proton transfer reactions also allows it to interact with other soil components, influencing the availability and uptake of nutrients by plants. The widespread use of H2PO4--containing fertilizers in agriculture highlights the significant impact this polyatomic ion has on supporting the global food supply.