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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 10c

Write the formula for the conjugate base for each of the following acids:
c. HPO42-

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1
Identify the definition of a conjugate base: A conjugate base is formed when an acid donates a proton (H⁺). This means the acid loses one hydrogen ion, and the charge of the species decreases by 1.
Start with the given acid, HPO₄²⁻. This species has one hydrogen atom that can be donated as a proton (H⁺).
Remove one hydrogen ion (H⁺) from HPO₄²⁻. This results in the chemical formula PO₄³⁻ because the removal of H⁺ decreases the charge by 1.
Verify the result: The conjugate base of HPO₄²⁻ is PO₄³⁻. This makes sense because the acid has donated a proton, leaving behind the phosphate ion with a charge of -3.
Write the final formula for the conjugate base: PO₄³⁻.

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Key Concepts

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

Conjugate Base

A conjugate base is the species that remains after an acid donates a proton (H⁺). In the context of Brønsted-Lowry theory, when an acid loses a proton, it transforms into its conjugate base, which can then potentially accept a proton in future reactions. Understanding this concept is crucial for predicting the behavior of acids and bases in chemical reactions.
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Acid-Base Reaction

An acid-base reaction involves the transfer of protons between reactants. In these reactions, acids donate protons while bases accept them. Recognizing the nature of these reactions helps in identifying the conjugate pairs, which is essential for determining the conjugate base of a given acid.
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Phosphate Ion

The phosphate ion (PO₄³⁻) is a polyatomic ion that plays a significant role in biochemistry and inorganic chemistry. In the case of HPO₄²⁻, it is a dihydrogen phosphate ion, which can lose a proton to form its conjugate base, PO₄³⁻. Understanding the structure and charge of phosphate ions is important for correctly identifying their conjugate bases.
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