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Questions and Answers
What is the primary mineral found in enamel, making it the hardest substance in the human body?
How is tooth decay prevented and enamel strengthened in toothpaste?
What is the primary way in which tooth cavities are formed?
Which compound is used to transform enamel into a more acid-resistant form, aiding in preventing tooth decay?
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What is the maximum permissible concentration of fluoride ion in drinking water without causing harm to teeth and bones?
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Which group 15 element is considered amphoteric?
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What is the primary industrial source of ammonia?
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Which compound is commonly used in the food industry as a preservative, often present in cured meats?
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When nitric acid reacts with an alkali metal, what is the general type of reaction that occurs?
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Which process is used to convert nitrogen and hydrogen into ammonia at an industrial scale?
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Study Notes
Enamel and Tooth Cavities
- Enamel is the hardest substance in the human body, containing 96% minerals, primarily hydroxyapatite (3Ca3(PO4)2.Ca(OH)2).
- When pH levels drop below 5.5, tooth cavities form as acid dissolves tooth enamel.
- Sugars and acids from candies and soft drinks contribute to tooth decay and enamel destruction.
- Fluoride causes remineralization into fluoridated hydroxyapatite and fluorapatite, which resist acid attacks better than the original tooth enamel.
Fluoride and Drinking Water
- The maximum permissible concentration of fluoride ions in drinking water is 1 ppm.
- Excess fluoride can cause brown mottling of teeth and harm to bones.
Nitrogen Compounds
Dinitrogen (N2)
- Dinitrogen is a colourless, odorless, diamagnetic gas at room temperature.
- It is very unreactive due to its high bond dissociation energy and lack of bond polarity.
- Industrial method of preparation: fractional distillation of air.
- Lab method of preparation: heating of metal azides.
Ammonia (NH3)
- Preparation: from metal nitrides, from ammonium salts, and by Haber's process.
- Properties: colourless, pungent smell, weakly basic, and very soluble in water.
- Reaction with metal salts: forms insoluble precipitates.
- Reaction with acids: forms ammonium salts.
Nitrous Oxide (N2O)
- Also known as laughing gas.
- Other names: nitrogen monoxide, nitrogen oxide.
- Structure: linear.
- Preparation: oxidation of ammonia, reaction of nitric oxide with hydrogen.
- Properties: colourless, sweet odor, neutral oxide gas.
Nitric Oxide (NO)
- Other names: nitrogen monoxide, nitrogen oxide.
- Structure: bent shaped.
- Preparation: controlled oxidation of ammonia, reaction of nitrous oxide with oxygen.
- Properties: colourless, paramagnetic, and a strong oxidiser.
Dinitrogen Trioxide (N2O3)
- Other names: nitrogen sesquioxide.
- Structure: planar.
- Preparation: reaction of nitric oxide with nitrous oxide.
- Properties: blue, acidic oxide liquid.
Dinitrogen Tetroxide (N2O4)
- Other names: nitrogen tetroxide.
- Structure: planar.
- Preparation: reaction of nitric oxide with oxygen.
- Properties: colourless, acidic oxide gas.
Dinitrogen Pentoxide (N2O5)
- Other names: nitrogen pentoxide.
- Structure: planar.
- Preparation: reaction of nitric oxide with oxygen.
- Properties: colourless, strongly acidic oxide solid.
Nitric Acid (HNO3)
- Preparation: Ostwald's process, lab process.
- Properties: colourless, strong acid, powerful oxidiser.
- Reaction with metals: forms nitrates.
- Reaction with non-metals: forms nitric oxide.
Phosphorus and Its Allotropes
White Phosphorus (P4)
- Preparation: heating of phosphate rocks.
- Properties: waxy solid, garlic-like smell, highly toxic, and highly reactive.
- Reaction with alkali: forms phosphine.
Red Phosphorus (P)
- Preparation: heating of white phosphorus.
- Properties: reddish-brown solid, non-toxic, and less reactive than white phosphorus.
- Reaction with alkali: forms phosphine.
Black Phosphorus (P)
- Preparation: heating of white phosphorus.
- Properties: thermodynamically stable, black solid, and a semiconductor.
- Reaction with alkali: forms phosphine.
Phosphine (PH3)
- Preparation: reaction of white phosphorus with alkali, reaction of phosphorus with hydrogen.
- Properties: colourless, highly toxic, and highly reactive gas.
- Reaction with air: forms diphosphine.
Phosphorus Trichloride (PCl3)
- Preparation: reaction of phosphorus with chlorine.
- Properties: colourless, oily liquid, and highly reactive.
- Reaction with water: forms phosphorous acid.
Phosphorus Pentachloride (PCl5)
- Preparation: reaction of phosphorus trichloride with chlorine.
- Properties: yellowish-white solid, and highly reactive.
- Reaction with water: forms phosphoric acid.
Group 15 Elements (Pnictogens)
Nitrogen (N)
- Atomic number: 7.
- Atomic mass: 14.01.
- Occurrence: found in proteins, earth's crust, and atmospheric gases.
Phosphorus (P)
- Atomic number: 15.
- Atomic mass: 30.97.
- Occurrence: found in phosphate rocks, milk, and eggs.
Arsenic (As)
- Atomic number: 33.
- Atomic mass: 74.92.
- Occurrence: found in minerals, and as a byproduct of copper and lead ores.
Antimony (Sb)
- Atomic number: 51.
- Atomic mass: 121.76.
- Occurrence: found in minerals, and as a byproduct of lead and copper ores.
Bismuth (Bi)
- Atomic number: 83.
- Atomic mass: 208.98.
- Occurrence: found in minerals, and as a byproduct of lead and copper ores.
Moscovium (Mc)
- Atomic number: 115.
- Atomic mass: 290.00.
- Occurrence: synthetic element.
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Description
Learn about the composition of tooth enamel, the role of minerals like hydroxyapatite, and how acids from sugary foods lead to tooth decay. Discover how fluoride helps in remineralisation and protects against acid attacks.
