Question

Which of the following statements is not correct? (1) Be like Al does not dissolve in alkalies. (2) Oxides of both Be and Al are amphoteric. (3) \(\mathrm{BeC}_{2}\) like \(\mathrm{Al}_{4} \mathrm{C}_{3}\) is covalent. (4) Burning of lime stone containing more than \(10 \%\) aluminium silicates gives hydraulic mortar.

Short answer

Statement (1) is not correct. Beryllium dissolves in alkalies.

Step-by-step solution

- Identifying Each Statement

Read each statement to understand what it claims. Analyze for any grammatical or scientific inconsistencies.

- Checking Statement 1

Statement 1 claims \( \text{Be like Al does not dissolve in alkalies}\). Beryllium (Be) actually dissolves in alkalies, forming complexes like \( \text{\[Be(OH)_4\]^{2-}}\). Therefore, this statement is incorrect.

- Checking Statement 2

Statement 2 claims \( \text{Oxides of both Be and Al are amphoteric}\). Both beryllium oxide (BeO) and aluminum oxide (Al2O3) are well-known to be amphoteric, so this statement is correct.

- Checking Statement 3

Statement 3 claims \( \text{BeC2 like Al4C3 is covalent}\). \( \text{Both BeC2 and Al4C3 are covalent in nature}\), so this statement is correct.

- Checking Statement 4

Statement 4 claims \( \text{Burning of limestone containing more than 10% aluminium silicates gives hydraulic mortar}\). This is known to be correct as hydraulic mortar is formed when such limestone is burned.

Conclusion

After analyzing each statement, we conclude that Statement 1 is incorrect.

Key concepts

Amphoteric Oxides

Amphoteric oxides are unique because they can react with both acids and bases. This means they have dual properties, acting sometimes as acids and other times as bases. For example, beryllium oxide (BeO) and aluminum oxide (Al2O3) are well-known amphoteric oxides. When BeO reacts with acids, it forms beryllium salts, and with bases, it forms beryllates. Similarly, Al2O3 can dissolve in acids to form aluminum salts and in strong bases to form aluminates. This characteristic makes amphoteric oxides quite versatile in chemical reactions and is crucial in understanding beryllium and aluminum chemistry.

Beryllium Chemistry

Beryllium (Be) holds a special place in inorganic chemistry due to its unique properties and behavior. Unlike other alkaline earth metals, Be forms covalent bonds rather than ionic ones.
The noteworthy part is its reaction with alkalies. While most metals do not dissolve in alkalies, Be is an exception. It reacts with strong bases like sodium hydroxide (NaOH) to form a beryllate complex \[Be(OH)_4^{2-}\]. This behavior is an important point of differentiation between Be and other elements.
In addition, BeC2 (beryllium carbide) is a covalent compound similar to aluminum carbide (Al4C3). These similarities between Be and Al make beryllium an interesting study in comparison with elements across the periodic table.

Aluminum Silicates

Aluminum silicates are significant in both geology and materials science. These compounds are composed of aluminum, silicon, and oxygen, often with additional metal ions. When limestone, which contains more than 10% aluminum silicates, is burned, it produces hydraulic mortar. Hydraulic mortar can harden underwater and is widely used in construction.
Comprehending the role of aluminum silicates in hydraulic mortar helps in many practical applications, such as building materials that need to withstand moisture and environmental conditions. This knowledge is also valuable for understanding soil chemistry and cement composition, where aluminum silicates are commonly found.