Question

Acetate ion, \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-},\) has a stronger affinity for protons than does water. Therefore, when dissolved in water, acetate ion behaves as a(n)

Short answer

The acetate ion \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-}\) behaves as a base in water, according to the Brønsted-Lowry theory, because it has a stronger affinity for protons than water and acts as a proton acceptor.

Step-by-step solution

Understand the affinity for protons in water

In the context of this problem, when we talk about the affinity for protons, we are referring to the tendency of a species to accept or donate protons (\(\mathrm{H}^{+}\)) in water. If a species has a stronger affinity for protons, it means that it is more likely to accept protons from water compared to water itself, which can also accept and donate protons under certain circumstances.

Define acids and bases according to the Brønsted-Lowry theory

According to the Brønsted-Lowry theory, an acid is a proton donor and a base is a proton acceptor. In water, an acid donates protons to the water molecules, while a base accepts protons from the water molecules.

Relate the affinity for protons to the behavior of the acetate ion in water

As mentioned in the exercise, the acetate ion (\(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-}\)) has a stronger affinity for protons than water does. This means that the acetate ion is more likely to accept protons from water molecules compared to water itself. In other words, the acetate ion is acting as a proton acceptor in water.

Determine the behavior of the acetate ion in water based on its affinity for protons

Since the acetate ion is acting as a proton acceptor in water, it is exhibiting basic behavior, according to the Brønsted-Lowry theory. So, the acetate ion behaves as a base in water.

Key concepts

Affinity for Protons

In the context of the Brønsted-Lowry theory, understanding the concept of affinity for protons is crucial. Affinity for protons refers to how strongly a substance can attract and hold onto protons, symbolized as \( \mathrm{H}^{+} \). This concept is significant when considering interactions in water, where many reactions occur. Here, water itself can donate or accept protons, functioning as either an acid or a base depending on the circumstances.

• If a substance exhibits a higher affinity for protons than water, it will more readily attract protons from water molecules compared to water's own ability to do so.
• This makes the substance a candidate for basic behavior, as it is likely to accept protons in the process.

Thus, understanding a material's affinity for protons lets us predict its role in chemical reactions: whether it acts more like an acid or a base.

Acid-Base Behavior

The Brønsted-Lowry theory is a well-known model that describes acid-base behavior based on the movement of protons. According to this theory:

• An acid is a proton donor. It releases protons to another substance.
• A base is a proton acceptor. It receives protons from an acid.

In water, the behavior of a chemical compound as either an acid or a base depends on its interactions with water molecules. Water serves as an amphiprotic substance, meaning it can act as either an acid or a base, depending on its environment.
When a compound like the acetate ion is introduced into water and begins accepting \( \mathrm{H}^{+} \) ions from water, it behaves as a base. This is due to its increased affinity for protons compared to water, directing us to classify it as a base under the Brønsted-Lowry definition.

Acetate Ion

The acetate ion, denoted as \( \mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}^{-}\), is an important player in acid-base reactions, particularly due to its tendency to attract protons.
### Characteristics of the Acetate Ion- **Structure and Charge**: Being negatively charged, it seeks the addition of a proton to stabilize its electronic structure.- **Chemical Behavior**: In an aqueous environment, the acetate ion behaves more dominantly as a proton acceptor.
In the Brønsted-Lowry framework, because the acetate ion has a stronger affinity for protons than water, it will more likely attract protons from water molecules, displaying its basic nature. This characteristic highlights the acetate ion's role in shifting equilibrium and manifests its significant basic properties when dissolved in water.