Chapter 4: Problem 30
Identify each of the following species as a Brønsted acid, base, or both: (a) HI, (b) \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-},\) (c) \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\), (d) \(\mathrm{HSO}_{4}^{-}\).
Short Answer
Expert verified
(a) Acid; (b) Base; (c) Both; (d) Both.
Step by step solution
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Proton Donor
In the realm of chemistry, a proton donor is another name for a Brønsted acid. These substances have the ability to donate a proton, specifically a hydrogen ion (
H^+
), during chemical reactions. The process of donating a proton transforms the original molecule, creating a new product.
For instance, in the case of hydrogen iodide (HI), the substance donates its proton to become iodide ( I^- ). This transformation is a key characteristic of Brønsted acids. Essentially, when you think of proton donors, think of substances eager to give away their extra hydrogen ions to partake in and drive chemical reactions.
Understanding which species can donate protons helps in identifying them as Brønsted acids and predicting their behavior in reactions.
For instance, in the case of hydrogen iodide (HI), the substance donates its proton to become iodide ( I^- ). This transformation is a key characteristic of Brønsted acids. Essentially, when you think of proton donors, think of substances eager to give away their extra hydrogen ions to partake in and drive chemical reactions.
Understanding which species can donate protons helps in identifying them as Brønsted acids and predicting their behavior in reactions.
Proton Acceptor
A proton acceptor is a term used to describe a Brønsted base. These entities have the ability to accept a proton from their surroundings, which leads to the formation of a new molecule.
When a substance acts as a proton acceptor, it typically starts with a negative charge or a lone pair of electrons that can easily accommodate an incoming proton.
For example, the acetate ion ( C_2H_3O_2^- ) acts as a proton acceptor by bonding with a proton to form acetic acid ( CH_3COOH ). By accepting this proton, the substance is stabilized and transformed, showcasing typical behavior of Brønsted bases.
Recognizing proton acceptors is crucial for understanding how certain reactions progress, as they guide the transfer and transformation of protons throughout the process.
When a substance acts as a proton acceptor, it typically starts with a negative charge or a lone pair of electrons that can easily accommodate an incoming proton.
For example, the acetate ion ( C_2H_3O_2^- ) acts as a proton acceptor by bonding with a proton to form acetic acid ( CH_3COOH ). By accepting this proton, the substance is stabilized and transformed, showcasing typical behavior of Brønsted bases.
Recognizing proton acceptors is crucial for understanding how certain reactions progress, as they guide the transfer and transformation of protons throughout the process.
HI Classification
Hydrogen iodide, written chemically as HI, is a classic example of a Brønsted acid. This classification stems from its capacity to donate a proton, a fundamental requirement for any Brønsted acid.
When HI gives away its proton, it leaves behind an iodide anion ( I^- ). This reaction forms new compounds and is indicative of HI's behavior as a Brønsted acid.
Overall, knowing specific molecules like HI helps further understand the broader concept of acids and their roles in chemical reactions. Knowing it donates protons is essential to classifying it correctly in reactions with other substances.
When HI gives away its proton, it leaves behind an iodide anion ( I^- ). This reaction forms new compounds and is indicative of HI's behavior as a Brønsted acid.
Overall, knowing specific molecules like HI helps further understand the broader concept of acids and their roles in chemical reactions. Knowing it donates protons is essential to classifying it correctly in reactions with other substances.
H₂PO₄⁻ Amphoteric Behavior
The concept of amphoteric behavior refers to a molecule's ability to act both as an acid and a base, depending upon the circumstances. The dihydrogen phosphate ion (
H_2PO_4^-
) brilliantly exemplifies this unique dual behavior.
As an acid, H_2PO_4^- can donate a proton, transforming into HPO_4^{2-} . This ability to lose a proton to another molecule highlights its acidic properties.
On the flip side, when acting as a base, H_2PO_4^- accepts a proton, forming H_3PO_4 (phosphoric acid). This addition of a proton underscores its basic capabilities.
Understanding amphoteric behavior is important in assessing how certain compounds react diversely under varying conditions, providing more dynamic roles in chemical equations.
As an acid, H_2PO_4^- can donate a proton, transforming into HPO_4^{2-} . This ability to lose a proton to another molecule highlights its acidic properties.
On the flip side, when acting as a base, H_2PO_4^- accepts a proton, forming H_3PO_4 (phosphoric acid). This addition of a proton underscores its basic capabilities.
Understanding amphoteric behavior is important in assessing how certain compounds react diversely under varying conditions, providing more dynamic roles in chemical equations.
