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Questions and Answers
What are the main group III-A elements?
What are the main group III-A elements?
Boron, Aluminum, Gallium, Indium, Thallium
Which of the following elements can be considered abundant?
Which of the following elements can be considered abundant?
Aluminum can only form ionic bonds.
Aluminum can only form ionic bonds.
False
What happens to the metals of group III-A when heated in air?
What happens to the metals of group III-A when heated in air?
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The hydroxides of group III-A elements tend to show __________ properties.
The hydroxides of group III-A elements tend to show __________ properties.
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What is the chemical equation for the reaction of aluminum hydroxide with hydrochloric acid?
What is the chemical equation for the reaction of aluminum hydroxide with hydrochloric acid?
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What is the formula for boric acid?
What is the formula for boric acid?
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What is one of the uses of sodium borate (Borax)?
What is one of the uses of sodium borate (Borax)?
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Match the following borate buffer systems with their features:
Match the following borate buffer systems with their features:
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What is a major adverse effect associated with aluminum?
What is a major adverse effect associated with aluminum?
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Study Notes
Group III-A Elements: The Boron Family
- Boron, aluminum, gallium, indium, and thallium are part of the boron family, with boron and aluminum being the most relevant in pharmacy.
- Aluminum is the most common metal and the third most common element in the Earth's crust.
Chemical Properties
- Boron bonding leans towards covalent rather than ionic, making it a metalloid.
- Aluminum forms both covalent and ionic bonds.
- Metals in this group readily oxidize when heated but remain stable at room temperature.
- The oxides can be easily reduced back to their metal form.
- These metals readily react with sulfur and halogens.
- Hydroxides generally exhibit amphoteric properties, except for the first and last elements in the group.
Chemical Equations
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Oxidation:
- 4M + 3 O2 2 M2O3 (where M represents Al or B)
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Reaction with Halogens:
- 2M + 3 X2 2 MX3 (where M represents Al or B)
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Reaction with Acids:
- Al(OH)3 + 3 HCl AlCl3 + 3 H2O
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Reaction with Bases:
- Al(OH)3 + NaOH NaAlO2 + 2 H2O
Identification Test for Aluminum
- When ammonia (NH3) is added, a white gelatinous precipitate of Al(OH)3 forms.
- Al(OH)3 can adsorb dye colors, such as aluminon, producing a red lake.
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Thenard's Blue Test:
- Co(NO3)2 + NH3 Co(AlO2)2
- This reaction produces a blue ash, cobalt meta-aluminate.
Compounds and Their Uses
Boron
- Boron is a non-metal and a component of glass.
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Sources:
- Tincal: Na3BO3
- H3BO3 (Boric Acid)
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Uses:
- Crystalline boron's hardness makes it a valuable diamond substitute for glass cutting and gem polishing.
Borates
- Borates react with turmeric paper.
- They are used in vulcanizing rubber.
Boric Acid (H3BO3)
- Also known as "Boracic acid", "Sal sedativum", and "Sal sativum".
- Toxic by ingestion.
- Absorbed through broken skin.
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Pharmaceutical Applications:
- Buffer in ophthalmic preparations.
- Tonicity adjusting agent.
- E-VALUE=0.52.
- Antiseptic.
- Eyewash: 2.45% - 2.5%.
- Boroglycerin glycerite - suppository base.
Boromycin
- Isolated from Streptomyces antibioticus.
- Used as an anti-HIV agent in vitro.
Sodium Borate (Na2B4O7)
- Also known as "Borax" or Sodium tetraborate.
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Uses:
- Dobell's solution - an astringent or antiseptic wash for the throat and nose.
- Eye wash.
- Component of cold cream and sodium borate preparations.
Buffer Systems
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Phosphate Buffer System:
- Contains dihydrogen and monohydrogen phosphate ions, which are physiological buffer pairs found in the body.
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Disadvantage:
- Insoluble phosphate salts of metals like silver (Ag), zinc (Zn), and aluminum (Al).
- Supports microbial growth.
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Borate Buffer System:
- Used in preparations containing metals that would otherwise precipitate in the presence of phosphates.
- Caution: Borates are toxic; these buffer systems are suitable for external preparations, ophthalmic and nasal solutions, but contraindicated in parenteral solutions.
Primary Borate Buffer Systems
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Feldman's Buffer System (pH 7-8.2):
- Contains boric acid, sodium chloride (for isotonicity), and an alkaline solution containing sodium borate.
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Atkins and Pantin Buffer System (pH 7.6-11):
- Consists of an alkaline sodium carbonate solution and an acidic buffer solution of boric acid and sodium chloride.
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Gifford Buffer System (pH 6-7.8):
- Similar to Feldman's, but uses potassium chloride instead of sodium chloride, making it hypotonic.
Aluminum
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Sources:
- Cryolite: (Na3AlF6, sodium hexafluoroaluminate)
- Chief source: Bauxite ore
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Pharmaceutical Uses:
- Deodorant.
- Protectant.
- Antiseptic.
- Antiperspirant.
Aluminum Adverse Effects
- Constipation.
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Toxicity:
- Shaver's disease/Bauxite pneumoconiosis: A progressive lung disorder caused by exposure to aluminum oxide found in bauxite fumes.
Aluminum Compounds
- Aluminum Chloride: Astringent, antiseptic, and component of deodorant.
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Aluminum Hydroxide (Al(OH)3):
- Brand names: Amphojel, Cremalin gel.
- Adverse Events: Constipation, phosphate deficiency.
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Aluminum Phosphate (AlPO4):
- Brand name: Phosphagel.
- Antacid, astringent.
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Description
Test your knowledge on the Group III-A elements, including boron, aluminum, gallium, indium, and thallium. This quiz covers their chemical properties, bonding behaviors, and reactions. Perfect for students of chemistry and pharmacy.
