The exact answer is AsH4+, also known as the arsonium ion.
Understanding Conjugate Acids and Bases
In chemistry, the concept of conjugate acids and bases is fundamental to the Brønsted-Lowry acid-base theory. This theory defines acids and bases based on their ability to donate or accept protons (H+ ions).
Key principles include:
- Acids are proton donors: They lose an H+ ion.
- Bases are proton acceptors: They gain an H+ ion.
- When an acid donates a proton, it forms its conjugate base.
- When a base accepts a proton, it forms its conjugate acid.
Essentially, a conjugate acid-base pair consists of two species that differ by only one proton (H+).
The Chemistry of AsH3
Arsine (AsH3) is a molecule with a pyramidal structure, similar to ammonia (NH3). Like ammonia, AsH3 possesses a lone pair of electrons on the central arsenic atom, which allows it to act as a proton acceptor. This characteristic enables AsH3 to function as a Brønsted-Lowry base.
Formation of the Conjugate Acid
When AsH3 acts as a base, it accepts a proton (H+) from an acid. The addition of this proton results in the formation of its conjugate acid.
The reaction demonstrating the formation of the conjugate acid is:
AsH3 (base) + H+ (proton) → AsH4+ (conjugate acid)
The resulting ion, AsH4+, is called the arsonium ion. It carries a positive charge because it has gained a positively charged proton.
The Conjugate Base of AsH3
While the question specifically asks for the conjugate acid, it's insightful to also understand the conjugate base of AsH3, which is AsH2-. This illustrates AsH3's potential to also act as a very weak acid, donating a proton.
The reaction demonstrating the formation of the conjugate base is:
AsH3 (acid) → AsH2- (conjugate base) + H+ (proton)
This dual behavior indicates that AsH3 can exhibit amphoteric properties, acting as both a very weak acid and a base, depending on the chemical environment.
Summary of AsH3 Acid-Base Pairs
The table below summarizes the acid-base relationships involving AsH3:
| Species | Role | Corresponding Pair |
|---|---|---|
| AsH3 | Brønsted-Lowry Base | AsH4+ (Conjugate Acid) |
| AsH3 | Brønsted-Lowry Acid | AsH2- (Conjugate Base) |
Therefore, the conjugate acid of AsH3 is AsH4+, formed when AsH3 accepts a proton.
