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Ch.10 Acids and Bases and Equilibrium
Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 13th Edition
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353Not the one you use?Change textbook
Chapter 10, Problem 11c

Write the formula for the conjugate acid for each of the following bases:
c. H2PO4-

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1
Identify the base provided in the problem. In this case, the base is the dihydrogen phosphate ion, represented as H2PO4-.
Recall the definition of a conjugate acid. A conjugate acid is formed when a base accepts a proton (H⁺).
Add a proton (H⁺) to the base. This involves increasing the number of hydrogen atoms in the formula by one and adjusting the charge accordingly. The formula becomes H3PO4.
Verify the charge of the conjugate acid. Since the base H2PO4- has a charge of -1, adding a proton (H⁺) neutralizes this charge, resulting in a neutral molecule.
Write the final formula for the conjugate acid, which is H3PO4.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Conjugate Acid-Base Pair

A conjugate acid-base pair consists of two species that differ by the presence or absence of a proton (H⁺). When a base accepts a proton, it forms its conjugate acid. Understanding this relationship is crucial for identifying the conjugate acid of a given base, as it directly influences the acid-base equilibrium in chemical reactions.
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Phosphate Ion Chemistry

Phosphate ions, such as H₂PO₄⁻, are part of a family of polyatomic ions that play significant roles in biological systems and chemical reactions. The H₂PO₄⁻ ion is the dihydrogen phosphate ion, which can act as a weak acid or a base. Recognizing its structure and behavior is essential for determining its conjugate acid when it gains a proton.
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Protonation Process

Protonation is the process by which a molecule or ion gains a proton (H⁺), resulting in the formation of a conjugate acid. This process is fundamental in acid-base chemistry, as it alters the charge and reactivity of the species involved. Understanding how protonation affects the properties of ions like H₂PO₄⁻ is key to predicting the resulting conjugate acid.
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