Question

Classify the following as acid or base according to Bronsted-Lowry concept. (i) \(\mathrm{CH}_{3} \mathrm{COO}^{-}\) (ii) \(\mathrm{H}_{3} \mathrm{O}^{+}\) (iii) \(\mathrm{SO}_{4}^{2-}\) (iv) \(\mathrm{HCl}\) (1) (ii) (iii) (a) Bronsted Bronsted Bronsted Bronsted base base base acid (b) Bronsted Bronsted Bronsted Bronsted acid acid acid base (c) Bronsted Bronsted Bronsted Bronsted base acid base acid (d) Bronsted Bronsted Bronsted Bronsted acid acid base base

Short answer

According to the Bronsted-Lowry concept, (i) \(\mathrm{CH}_{3} \mathrm{COO}^{-}\) is a base, (ii) \(\mathrm{H}_{3} \mathrm{O}^{+}\) is an acid, (iii) \(\mathrm{SO}_{4}^{2-}\) is a base, and (iv) \(\mathrm{HCl}\) is an acid; the answer is option (c).

Step-by-step solution

Understand the Bronsted-Lowry Concept

According to the Bronsted-Lowry concept, an acid is a substance that can donate a proton (H+), while a base is a substance that can accept a proton.

Classify \(\mathrm{CH}_{3} \mathrm{COO}^{-}\)

The acetate ion (\(\mathrm{CH}_{3} \mathrm{COO}^{-}\)) can accept a proton to form acetic acid. Hence, it acts as a Bronsted-Lowry base.

Classify \(\mathrm{H}_{3} \mathrm{O}^{+}\)

The hydronium ion (\(\mathrm{H}_{3} \mathrm{O}^{+}\)) can donate a proton to form water. Therefore, it is a Bronsted-Lowry acid.

Classify \(\mathrm{SO}_{4}^{2-}\)

The sulfate ion (\(\mathrm{SO}_{4}^{2-}\)) can accept a proton to form hydrogen sulfate. Thus, it is a Bronsted-Lowry base.

Classify \(\mathrm{HCl}\)

Hydrochloric acid (\(\mathrm{HCl}\)) can donate a proton to form the chloride ion. Hence, it is a Bronsted-Lowry acid.

Match With Given Options

Comparing with the provided options, Bronsted-Lowry base (i), Bronsted-Lowry acid (ii), Bronsted-Lowry base (iii), Bronsted-Lowry acid (iv) match option (c).

Key concepts

Proton Donor

In the world of chemistry, understanding the behavior of acids and bases is crucial, and the Bronsted-Lowry concept provides a clear framework for this. An acid, according to this concept, is a substance known as a proton donor. But what exactly is a proton in this context? It refers to a hydrogen ion, symbolized as H+. In simpler terms, an acid is any molecule or ion that can give away an H+ ion to another substance.

For instance, when we look at hydrochloric acid (HCl), we can see it in action as an acid because it has the ability to hand off a hydrogen ion to another substance, leaving behind a chloride ion (Cl-). This quality of 'giving' is what earmarks it as a proton donor and thus, an acid in the Bronsted-Lowry classification.

Proton Acceptor

Conversely, a base in the Bronsted-Lowry acid-base concept is defined as a proton acceptor. This means the substance can receive or 'accept' a proton (H+) from another substance. This is easier to understand when we look at an example such as the acetate ion (CH3COO-). This ion accepts a proton and transforms into acetic acid.

The ability to accept a proton doesn't just identify the substance as a base; it can also trigger various chemical reactions. This concept of proton acceptance is a fundamental aspect of the acid-base chemistry that we encounter not only in labs but also in biological systems and many industrial processes.

Acid-Base Classification

Distinguishing between acids and bases is pivotal for predicting the outcomes of many chemical reactions. With the aid of the Bronsted-Lowry concept, we can categorize substances based on their function as proton donors or acceptors. For example, in the exercise provided, by understanding these roles, H3O+ is identified as a proton donor because it has an extra proton that it can give up. This classifies it as an acid. In contrast, SO42- can take on an additional proton, fitting the definition of a base.

Knowing these classifications can be quite advantageous in predicting the properties and reactions of chemical species. Hence, correctly labeling a compound as an acid or a base is not just academic semantics; it's a practical tool for students and scientists alike.

Chemical Properties of Acids and Bases

The chemical properties of acids and bases are fascinating and diverse. Acids, being proton donors, often have a sour taste and can turn blue litmus paper red, which is a classic experiment in chemistry classes. They react with metals to produce hydrogen gas and can neutralize bases in a neutralization reaction to form water and a salt.

On the flip side, bases, as proton acceptors, usually have a bitter taste and feel slippery, like soap. They turn red litmus paper blue and neutralize acids to also form water and a salt. Moreover, bases can conduct electricity when dissolved in water, a property known as being 'electrolytic'. These properties play a significant role in a wide range of industrial applications, from cleaning products to food manufacturing. Understanding them is not just useful for solving exercises but also for applying this knowledge in real-world scenarios.