A crystalline form of aluminum oxide used as an abrasive and gemstone
Explication
Corundum is a crystalline form of aluminum oxide (Al₂O₃) known for its hardness and used as an abrasive and gemstone, making option 0 the correct answer.
H3BO3
Explication
The chemical formula of boric acid, which is used as a mild antiseptic and disinfectant, is H3BO3. The other options are different boron compounds: borax (Na2B4O7·10H2O), boron nitride (BN), and alum (AlK(SO4)2·12H2O).
They serve primarily as durable abrasive materials and gemstones.
Explication
Corundum and spinel are primarily valued for their durability and hardness. Corundum is used as an abrasive and as gemstones like sapphires and rubies, while spinel is prized in jewelry for its strength and attractive appearance. Their main function is as durable materials for industrial and ornamental purposes.
Around 3000 BCE in ancient Egypt
Explication
Beryl has been used as a gemstone since ancient times, with evidence of its use dating back to around 3000 BCE in ancient Egypt, making it one of the earliest known gemstones.
Corundum is a form of aluminum oxide used mainly as an abrasive and gemstone, while spinel is a magnesium aluminum oxide valued for jewelry due to its durability.
Explication
Corundum (Al₂O₃) is a crystalline form of aluminum oxide used as an abrasive and gemstone, while spinel (MgAl₂O₄) is a magnesium aluminum oxide mineral valued in jewelry for its durability. They differ in chemical composition and primary applications, with corundum being associated with sapphires and rubies, and spinel with colorful gemstones.
Joseph Louis Gay-Lussac
Explication
Joseph Louis Gay-Lussac is credited with the early preparation and study of boric acid (H3BO3), making him the correct answer. The distractors are notable chemists but are not associated with boric acid's discovery or proposal.
They enhance the fire resistance, durability, and manufacturing efficiency of products.
Explication
The properties of boron-based materials, such as their hardness, thermal stability, and reactivity, directly lead to their use in fire retardants, abrasives, and fluxes, thereby improving fire resistance, durability, and manufacturing processes.
Use as a disinfectant and antiseptic in medical treatments
Explication
Boric acid's chemical property of antimicrobial activity makes it suitable for use as a disinfectant and antiseptic in medical treatments, which is a practical application of its chemical nature.
Their extreme hardness and thermal stability
Explication
Boron nitride, especially in its cubic form known as Borazon, is valued in industry primarily for its extreme hardness and high thermal stability, making it suitable for cutting tools and abrasives.
It enhances the fire retardant properties of materials.
Explication
The interaction between aluminum hydroxide and boron compounds in industrial applications primarily enhances the fire retardant properties of materials, as both are used to improve fire resistance in textiles, plastics, and other materials.
Mémorisez les réponses avec 20 flashcards sur Fundamentals of Aluminum and Boron Compounds.
Al2O3 — definition?
Corundum, a crystalline aluminum oxide.
Cryolite — role?
Flux in aluminum electrolysis.
MgAl2O4 — use?
Jewelry and durable gemstones.
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