Question

Please help me answer this question for my Chemistry & Environmental Pollution subject. PLEASE answer it seriously and completely, or better not answer it if not then, really appreciate it, thank you.

Q2.

(a) Describe three primary types of clay minerals and how do they differ from one another. ( 10 marks )

(b) Define weathering processes and describe briefly the mechanism of chemical weathering. ( 10 marks )

Answer 1

Q2)

a)

Kaolinite Al2Si2O5(OH)2

Kaolinite clays have for quite some time been utilized in the clay business, particularly in fine porcelains, since they can be effectively shaped, have a fine surface and are white when terminated. These clays are additionally utilized as a filler in making paper. In the United States, stores are found principally in Georgia, North Carolina, what's more, Pennsylvania; china earth is moreover mined in England (Cornwall) and France.

Kaolinite Al2Si2O5(OH)4

Kaolinite is the most perfect of dirt, implying that it fluctuates little in a piece. It likewise does not ingest water and does not extend when it interacts with water. Accordingly, kaolinite is the favoured sort of earth for the earthenware business.

Montmorillonite

The most widely recognized smectite is Montmorillinite, with a general concoction equation :

(1⁄2Ca,Na)(Al,Mg,Fe)4(Si,Al)8O20(OH)4.nH2O

Montmorillinite is the principle constituent of bentonite, inferred by enduring of volcanic fiery debris. Montmorillinite can extend by a few times its unique volume when it comes in contact with water. This makes it valuable as a penetrating mud (to keep drill openings open), and to plug spills in soil, shakes, and dams. Montmorillinite, be that as it may, is a hazardous kind of mud to experience whether it is found in passages or then again street cuts. In light of its expandable nature, it can prompt genuine incline or divider disappointments.

b)

Definition of Chemical Weathering Definition

Chemical weathering is the procedure by which the mineral structures of rocks are changed. Concoction enduring can make minerals decay and even break up.

Chemical weathering is substantially more typical in areas where there is a great deal of water. It is the most significant procedure for soil development. Chemical weathering turns out to be increasingly compelling as the surface region of the stone increments. Since the compound responses happen to a great extent on the outside of the stones, in this manner the littler the sections, the more noteworthy the surface territory per unit volume accessible for the response.

Chemical weathering is debilitating and resulting in breaking down of shake by substance responses. These responses incorporate hydration, hydrolysis, carbonation, oxidation, and decrease. These procedures either structure or obliterate minerals, therefore adjusting the idea of the stone's mineral arrangement. Temperature and, particularly, dampness is basic for Chemical weathering.

Mechanism:

Following procedures are engaged with chemical weathering

1. Hydration
2. Hydrolysis
3. Carbonation
4. Oxidation
5. Reduction

Hydration

Hydration is a standout amongst the most well-known procedures in nature and works with optional minerals, for example, aluminum oxide and iron oxide minerals and gypsum. Soil shaping minerals in rocks don't contain any water and they experience hydration when presented to moist conditions.

2Fe₂O₃ + 3HOH   →     2Fe₂O₃ .3H₂O

   (Hematite) (Red)            (Limonite) (Yellow)

Al₂O₃ + 3HOH     →     Al₂O₃ .3H₂O

   (Bauxite)                      (Hyd. aluminum Oxide)

Hydrolysis

Hydrolysis is the most significant procedure in synthetic enduring. It is because of the separation of H2O into H+ and OH-particles which artificially join with minerals and realize changes, for example, trade, the decay of crystalline structure and development of new mixes.

KAlSi₃O₈ + H₂O       →        HAlSi₃O₈ + KOH

(Orthoclase)                       (Acid silt clay)

HAlSi₃O₈ + 8 HOH  → Al₂O₃ .3H₂O        +      6 H₂SiO₃

(Recombination) (Hyd. Alum. oxide)        (Silicic acid)

A few substances present in the stones are straightforwardly solvent in water. The solvent substances are evacuated by the ceaseless activity of water and the stone never again stays strong and structure openings, rills or harsh surface and at last falls into pieces or breaks down. The activity is extensively expanded when the water is fermented by the disintegration of natural and inorganic acids.

NaCl + H₂O → Na⁺, Cl^-

Carbonation

Carbon dioxide when broken up in the water it frames carbonic corrosive.

2H₂O + CO₂    →   H₂CO₃

This carbonic corrosive assaults numerous stones and minerals and brings them into the arrangement. The carbonated water has a drawing impact upon certain stones, particularly limestone. The expulsion of bond that holds sand particles together prompts their breaking down.

CaCO₃       +       H2CO₃   →     Ca(HCO₃)₂

(Calcite) (Ca bi carbonate)

Oxidation

Oxidation is the procedure of expansion and mix of oxygen to minerals. The retention is as a rule from O2 broke down in soil water and that present in the climate. The oxidation is increasingly dynamic within the sight of dampness and results in hydrated oxides.

4FeO (Ferrous oxide) + O₂     →   2Fe₂O₃ (Ferric oxide)

4Fe₃O₄ (Magnetite) + O₂       →   6Fe₂O₃ (Hematite)

2Fe₂O₃ (Hematite) + 3H₂O   →   2Fe₂O₃ .3H₂O (Limonite)

Reduction

The procedure of expulsion of oxygen and is the turn around of oxidation and is similarly significant in changing soil shading to dark, blue or green as ferric iron is changed over to ferrous iron mixes. Under the states of abundance water or waterlogged condition (less or no oxygen), decrease happens.

2Fe₂O₃ (Hematite) - O₂ → 4FeO (Ferrous oxide)