Chemical Weathering: Hydration Reactions

Chemical Weathering

Chemical weathering is the breakdown of rocks into smaller particles through chemical reactions.

Hydration

• Hydration is a type of chemical weathering that involves the reaction of water with minerals in rocks.
• Water molecules (H2O) react with mineral ions to form new compounds, increasing the volume of the rock and causing it to break apart.
• Examples of hydration reactions include:
  • Calcite (CaCO3) + H2O → Ca(OH)2 + CO2
  • Anhydrite (CaSO4) + H2O → Gypsum (CaSO4·2H2O)

Hydrolysis

• Hydrolysis is a type of chemical weathering that involves the reaction of water with minerals in rocks, resulting in the breakdown of the mineral structure.
• Hydrolysis reactions involve the substitution of H+ or OH- ions for other ions in the mineral, causing the mineral to break down.
• Examples of hydrolysis reactions include:
  • Feldspar (KAlSi3O8) + H2O → Kaolinite (Al2Si2O5(OH)4) + K+ + SiO2
  • Mica (KAl2(AlSi3O10)(OH)2) + H2O → Kaolinite (Al2Si2O5(OH)4) + K+ + SiO2

Oxidation

• Oxidation is a type of chemical weathering that involves the reaction of oxygen with minerals in rocks, resulting in the formation of new compounds.
• Oxidation reactions often involve the conversion of ferrous iron (Fe2+) to ferric iron (Fe3+), resulting in the formation of iron oxide compounds.
• Examples of oxidation reactions include:
  • Pyrite (FeS2) + O2 → Fe2O3 + S
  • Iron-rich minerals + O2 → Iron oxides (e.g. hematite, Fe2O3)

Carbonation

• Carbonation is a type of chemical weathering that involves the reaction of carbon dioxide (CO2) with water to form carbonic acid (H2CO3).
• Carbonic acid reacts with minerals in rocks, causing them to break down and dissolve.
• Examples of carbonation reactions include:
  • Calcite (CaCO3) + H2CO3 → Ca2+ + HCO3-
  • Silicate minerals + H2CO3 → Silicic acid + metal ions

Chemical Weathering

• Chemical weathering is the breakdown of rocks into smaller particles through chemical reactions.

Hydration

• Hydration is a type of chemical weathering that involves the reaction of water with minerals in rocks.
• Water molecules (H2O) react with mineral ions to form new compounds, increasing the volume of the rock and causing it to break apart.
• Examples of hydration reactions include:
  • Calcite (CaCO3) + H2O → Ca(OH)2 + CO2
  • Anhydrite (CaSO4) + H2O → Gypsum (CaSO4·2H2O)

Hydrolysis

• Hydrolysis is a type of chemical weathering that involves the reaction of water with minerals in rocks, resulting in the breakdown of the mineral structure.
• Hydrolysis reactions involve the substitution of H+ or OH- ions for other ions in the mineral, causing the mineral to break down.
• Examples of hydrolysis reactions include:
  • Feldspar (KAlSi3O8) + H2O → Kaolinite (Al2Si2O5(OH)4) + K+ + SiO2
  • Mica (KAl2(AlSi3O10)(OH)2) + H2O → Kaolinite (Al2Si2O5(OH)4) + K+ + SiO2

Oxidation

• Oxidation is a type of chemical weathering that involves the reaction of oxygen with minerals in rocks, resulting in the formation of new compounds.
• Oxidation reactions often involve the conversion of ferrous iron (Fe2+) to ferric iron (Fe3+), resulting in the formation of iron oxide compounds.
• Examples of oxidation reactions include:
  • Pyrite (FeS2) + O2 → Fe2O3 + S
  • Iron-rich minerals + O2 → Iron oxides (e.g. hematite, Fe2O3)

Carbonation

• Carbonation is a type of chemical weathering that involves the reaction of carbon dioxide (CO2) with water to form carbonic acid (H2CO3).
• Carbonic acid reacts with minerals in rocks, causing them to break down and dissolve.
• Examples of carbonation reactions include:
  • Calcite (CaCO3) + H2CO3 → Ca2+ + HCO3-
  • Silicate minerals + H2CO3 → Silicic acid + metal ions

Learn about chemical weathering through hydration reactions, where water interacts with minerals to break down rocks into smaller particles.