Physical properties: low melting point, low hardness, good electrical and thermal conductivity

Metal Na has strong reducing properties and is a typical active metal that reacts with O₂, Cl₂, H₂O, and H⁻

When reacting with a salt solution, it can be considered that the hydroxide radicals produced by reacting with water first undergo subsequent reactions.

Preparation of Na element: 2NaCl(melted)═Electrolysis═2Na Cl₂↑

application

Moderately strong oxidizing property of Na₂O₂

Compared

2Na₂O₂～O₂～2e⁻, n（Na₂O₂）=2n（O₂）=n（e⁻）

Gas variable relationship: If CO₂ and water vapor are combined with a sufficient amount of Na₂O₂, the reduction in gas volume is 1/2 of the original gas volume, which is equal to the amount of oxygen generated, ΔV=V (O₂)=1/2V total

Solid increment relationship: When carbon dioxide and water vapor react with a sufficient amount of Na₂O₂, the solid is equivalent to absorbing the "CO" water in CO₂ and the "H₂" in the steam. The increased mass of the solid is Δm (solid) = 28g·mol⁻¹×n (CO₂), Δm (solid) = 2g·mol⁻¹×n (H₂O)

Float: Less dense than water

Melting: The reaction is exothermic, and sodium has a low melting point

Swim: Produce gas to push sodium to swim

Sound: Violent reaction

Red: Strong base NaOH is generated

Solid state (heating): A colorless and odorless gas that turns clear limewater cloudy is produced, which is NaHCO ₃

liquid

CO₂ and NaOH

Na₂CO₃, NaHCO₃ and NaOH with HCl

Note: HCl always reacts with NaOH first, then Na₂CO₃, then NaHCO₃

Reaction principle: NaCl CO₂ H₂O NH₃═NaHCO₃↓ NH₄Cl 2NaHCO₃═ΔNa₂CO₃ H₂O CO₂↑

Principle: NH₃ H₂O CO₂═NH₄HCO₃ NH₄HCO₃ NaCl═NaHCO₃↓ NH₄Cl

Recycling: CO₂, NaCl

Al

Al₂ O₃

physical properties

Chemical properties (ambiteric)

preparation

physical properties

chemical properties

FeO

Fe₂O₃

Fe₃O₄

Sample solution → Add KSCN solution dropwise → No phenomenon → Add chlorine water or hydrogen peroxide dropwise → If the solution turns red, it proves the presence of Fe²⁺

Sample solution → Add sodium hydroxide solution → A white flocculent precipitate is produced, which quickly turns gray-green and finally reddish-brown, proving that it contains Fe²⁺

Sample solution → Add acidic KMnO₄ → KMnO₄ dropwise, the purple-red color of the solution fades, proving that it contains Fe²⁺

Sample solution → Add K₃[Fe(CN)₆] solution dropwise → A blue precipitate will appear, indicating that the solution contains Fe²⁺ 3Fe²⁺ 2【Fe（CN）₆】³⁻═Fe₃【Fe（CN）₆】↓

In the laboratory, FeCl₃, a saturated solution can be dropped into boiling water to prepare ferric hydroxide colloid. Reaction equation: FeCl₃ 3H₂O ═Δ═Fe(OH)₃ (colloid) 3HCl

A commonly used method in industry is to adjust the pH to remove iron ions from the solution.

Sample solution → add KSCN solution dropwise → easily turns red, proving the presence of Fe³⁺

Sample solution → Add sodium hydroxide solution → Reddish-brown precipitate is produced, proving the presence of Fe³⁺

Sample solution → Add phenol (C₆H₅OH), add phenol to the FeCl₃ solution, the solution will appear purple

white solid

Reacts with hydrochloric acid: Fe(OH)₂ 2H⁺═Fe²⁺ 2H₂O

Strong reducing property: 4Fe(OH)₂O₂ 2H₂O═4Fe(OH)₃

Preparation method

Reddish brown solid

Reacts with hydrochloric acid: Fe(OH)₃ 3H⁺═Fe³⁺3H₂O

Decomposition by heating: 2Fe(OH)₂═Δ═Fe₂O₃ 3H₂O

Strong oxidizing property: 2Fe(OH)₃ 6H⁺ 2I⁻═2Fe²⁺ 6H₂O I₂

Preparation method: Soluble iron salt reacts with salt solution Fe³⁺ 3OH⁻═Fe(OH)₃↓

Silvery white, solid with metallic luster

Density and hardness are both small

Lower melting point

Has good electrical conductivity, thermal conductivity and ductility

Reacts with N₂: 2Mg CO₂