Химия. Экология. Медицина



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MINERALS ARE EARTH’S TREASURES

Jennifer Ileka, group 3. Science adviser is Svetlana Kozub.


A mineral can be defined as a naturally occurring inorganic solid that possesses an orderly internal structure and a definite chemical composition.

Minerals can be classified in many ways such as hardness and crystal structure.

There are over 300 minerals known. Minerals are composed of elements

A rare earth mineral is a mineral which contains one or more rare earth elements as major metal constituents. Rare earth minerals are usually found in association with alkaline to peralkalineigneous complexes, in pegmatites associated with alkaline magmas and in or associated with carbonatite intrusives. Perovskite mineral phases are common hosts to rare earth elements within the alkaline complexes. Mantle derived carbonate melts also are carriers of the rare earths. Hydrothermal deposits associated with alkaline magmatism contain a variety of rare earth minerals.



TYPES OF CHEMICAL REACTIONS

Rautia Matheus, group 3. Science adviser is Svetlana Kozub.


A chemical reaction is a process that is usually characterized by a chemical change in which the starting materials (reactants) are different from the products. Chemical reactions tend to involve the motion of electrons, leading to the formation and breaking of chemical bonds. There are several different types of chemical reactions and more than one way of classifying them. Here are some common reaction types. Direct Combination or Synthesis Reaction

In a synthesis reaction two or more chemical species combine to form a more complex product.

A + B → AB

The combination of iron and sulfur to form iron (II) sulfide is an example of a synthesis reaction:

8 Fe + 8S → 8 FeS

• Chemical Decomposition or Analysis Reaction

In a decomposition reaction a compound is broken into smaller chemical species.

AB → A + B

The electrolysis of water into oxygen and hydrogen gas is an example of a decomposition reaction:

2 H2O → 2 H2 + O2

• Single Displacement or Substitution Reaction

A substitution or single displacement reaction is characterized by one element being displaced from a compound by another element.

A + BC → AC + B

An example of a substitution reaction occurs when zinc combines with hydrochloric acid. The zinc replaces the hydrogen:

Zn + 2 HCl → ZnCl2 + H2

• Metathesis or Double Displacement Reaction

In a double displacement or metathesis reaction two compounds exchange bonds or ions in order to form different compounds.

AB + CD → AD + CB

An example of a double displacement reaction occurs between sodium chloride and silver nitrate to form sodium nitrate and silver chloride.

NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(s)

Acid-Base Reaction

An acid-base reaction is type of double displacement reaction that occurs between an acid and a base. The H+ ion in the acid reacts with the OH- ion in the base to form water and an ionic salt:

HA + BOH → H2O + BA

The reaction between hydrobromic acid (HBr) and sodium hydroxide is an example of an acid-base reaction:

HBr + NaOH → NaBr + H2O

• Oxidation-Reduction or Redox Reaction

In a redox reaction the oxidation numbers of atoms are changed. Redox reactions may involve the transfer of electrons between chemical species.

The reaction that occurs when In which I2 is reduced to I- and S2O32- (thiosulfate anion) is oxidized to S4O62- an example of a redox reaction:

2 S2O32−(aq) + I2(aq) → S4O62−(aq) + 2 I(aq)

• Combustion

A combustion reaction is a type of redox reaction in which a combustible material combines with an oxidizer to form oxidized products and generate heat (exothermic reaction). Usually in a combustion reaction oxygen combines with another compound to form carbon dioxide and water. An example of a combustion reaction is the burning of naphthalene:

C10H8 + 12 O2 → 10 CO2 + 4 H2O

• Isomerization

In an isomerization reaction, the stuctural arrangement of a compound is changed but its net atomic composition remains the same.

• Hydrolysis Reaction

A hydrolysis reaction involves water. The general form for a hydrolysis reaction is:

X-(aq) + H2O(l) <--> HX(aq) + OH-(aq)

BLANC REACTION

Pranav Neelank Sharma, group 3. Science adviser is Svetlana Kozub.


This reaction, which is comparable to a Friedel-Crafts Alkylation , is useful for the preparation of chloromethylatedarenes (for example, the Merrifield resin based on polystyrene) from the parent arene with formaldehyde, HCl, and ZnCl2. Mechanism of the Blanc Reaction The Lewis acid ZnCl2 effects formation of an oxonium ion which is reactive in electrophilic aromatic substitution. The intermediate zinc alkoxide reacts with the arene to form the chloromethylated product and zinc oxides:

Dakin reaction :

The Dakin Reaction allows the preparation of phenols from aryl aldehydes or aryl ketones via oxidation with hydrogen peroxide in the presence of base. The aryl formate or alkanoate formed as an intermediate is subsequently saponified to yield the substituted phenol product.

Aldolreaction :

'Aldol' is an abbreviation of *ald*ehyde and alcoh*ol*. When the enolate of an aldehyde or a ketone reacts at the α-carbon with the carbonyl of another molecule under basic or acidic conditions to obtain β-hydroxy aldehyde or ketone, this reaction is called Aldol.

GATTERMAN – KOCH REACTION

Zainub Riyaz, group 3. Science adviser is Svetlana Kozub.


The Gattermann–Koch reaction, named after the German chemists Ludwig Gattermann and Julius Arnold Koch, in organic chemistry refers to a Friedel–Crafts acylation reaction in which carbon monoxide and hydrochloric acid are used in situ with Friedel–Crafts catalyst, namely AlCl3 to produce a benzaldehyde derivative from a benzene derivative in one step. Benzaldehyde and many aromatic aldehydes are conveniently synthesized by this reaction. Presence of traces of copper(I) chloride are also needed along with zinc chloride .An example would be the conversion of toluene to p-tolualdehyde.


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