Question

Which of the following statements is correct? (1) The hydroxide of aluminium is morc acidic than that of boron. (2) The hydroxide of boron is basic, whercas that of aluminium is ampthoteric. (3) The hydroxide of boron is acidic, whereas of aluminium is amphoteric. (4) The hydroxides of boron and aluminium are amphoteric.

Short answer

Statement (3) is correct: The hydroxide of boron is acidic, whereas that of aluminium is amphoteric.

Step-by-step solution

- Understanding the Concepts

Identify the chemical nature of the hydroxides of boron and aluminium. Boron typically forms boric acid (B(OH)_3), which is a weak acid. Aluminium forms aluminium hydroxide (Al(OH)_3), which is amphoteric (can act as both an acid and a base).

- Evaluating Each Statement

Evaluate each of the given statements: (1) The hydroxide of aluminium is more acidic than that of boron. This statement is incorrect because boric acid (B(OH)_3) is acidic, while aluminium hydroxide (Al(OH)_3) is amphoteric, not more acidic.(2) The hydroxide of boron is basic, whereas that of aluminium is amphoteric.This statement is incorrect because boric acid (B(OH)_3) is acidic, not basic, and aluminium hydroxide (Al(OH)_3) is amphoteric.(3) The hydroxide of boron is acidic, whereas that of aluminium is amphoteric.This statement fits the learned chemical properties correctly. Boric acid (B(OH)_3) is acidic and aluminium hydroxide (Al(OH)_3) is amphoteric.(4) The hydroxides of boron and aluminium are amphoteric.This statement is incorrect; boric acid (B(OH)_3) is not amphoteric but acidic.

- Conclusion

After evaluating all statements, it is clear that statement (3) accurately describes the properties of the hydroxides of boron and aluminium.

Key concepts

boron hydroxide

Boron hydroxide, commonly referred to as boric acid, has the chemical formula B(OH)_3. It is a weak acid and is known for its characteristic acidic nature. Boric acid does not act like a typical hydroxide; instead, it is mildly acidic, making it quite distinct among hydroxides. It dissociates slightly in water, contributing to its weakly acidic behavior.
Some practical applications of boric acid include its use in antiseptics, insecticides, and even as a buffer in chemical laboratories. Its relatively low acidity makes it useful for gentle applications where stronger acids would be too harsh.

aluminium hydroxide

Aluminium hydroxide, Al(OH)_3, is a noteworthy compound because of its amphoteric nature. This means it can act as both an acid and a base. In acidic environments, it can accept protons to form aluminium ions, while in basic conditions, it can donate protons to yield aluminates. This dual behavior is rare and is an important concept in chemistry.
Aluminium hydroxide is commonly used in antacids due to its ability to neutralize stomach acid. Additionally, it finds applications in water purification and as a fire retardant due to its chemical properties.
The amphoteric characteristic makes Al(OH)_3 crucial in various chemical reactions and industrial processes.

amphoteric substances

Amphoteric substances are unique chemicals that can react with both acids and bases. Aluminium hydroxide is a classic example of an amphoteric compound. This versatility arises from its ability to both donate and accept protons, depending on the surrounding environment.
Understanding amphoteric behavior is essential for chemistry students as it explains many reaction mechanisms. For instance, in an acidic solution, aluminium hydroxide reacts as a base, while in a basic medium, it behaves like an acid. This dual behavior is exploited in various industrial processes.
Not all substances are amphoteric, making those that are particularly useful and interesting in both theoretical and practical chemistry.

acidic nature

Acidity is a key concept in chemistry and refers to a substance's ability to donate protons (H^+ ions). Boron hydroxide, or boric acid, exemplifies a substance with weak acidic nature. It releases few hydrogen ions in solution, which makes it less aggressive compared to strong acids like hydrochloric acid.
The acidity level of a substance is measured by its pH value, with lower values indicating higher acidity. Boric acid, with its mild acidity, is preferred in applications where a gentle acidic effect is required.
Understanding acid strength and behavior aids in predicting the outcomes of chemical reactions, which is fundamental for both academic study and practical applications.

chemical evaluation

Chemical evaluation involves analyzing and understanding the properties and reactions of substances. In the context of the original exercise, it meant determining the correct statements about boron and aluminium hydroxides by evaluating their chemical properties.
Through systematic evaluation, we identified boric acid as weakly acidic and aluminium hydroxide as amphoteric. Such evaluations rely on knowledge of chemical behavior, reaction mechanisms, and empirical observations.
For students, honing the skill of chemical evaluation is crucial; it involves critically assessing information and applying theoretical knowledge to practical problems. This skill is beneficial not only academically but also in chemical research and industry practices.