CHEMICAL REACTION
Face to face material 11
Chemistry science is the study of the structure, structure, properties,
changes in matter and energy that accompanies such changes. In Chemistry, water
and alcohols are compounds, which are a combination of two or more substances
with certain compositions. Alcohol can burn because carbon, oxygen and hydrogen
in it form a less stable bond and can join or react with oxygen in the air,
forming a more stable bond.
What is a chemical reaction?
Chemical reaction is a
process where by new substances, the reaction product, are formed from some of
the original substances called reagents. Usually a chemical reaction is
accompanied by physical events, such as: color change, sediment formation,
release of gas and energy release and energy absorption.
If there is a chemical reaction, it can be observed 3 kinds of changes,
namely:
A. Change of nature
B. Change of order
C. Energy changes
All chemical changes
are certainly parent on the law of preservation of energy laws and the law of
mass energy preservation. The fundamental fundamentals underlying all chemical
change are theoretical chemistry areas, the correlation between the concept of
elements and compounds, with the laws formed above being obtained in Dalton's
Theomic Theory, the first modern theory of atoms and molecules as fundamental
particles of substances that grow from this theory. The most important thing
from the Dalton atomic theory that can now be accepted, namely:
1.
Atom is a building unit of all kinds of material
2. Atom is a small part of an element that still has the same properties with its elements.
3. In chemical reactions, atoms are not destroyed, not created and can not be converted into atoms of other elements.
Chemical reactions are simply rearrangement of the arrangement of atoms involved in the reaction.
The types of chemical reactions, namely:
A. Burning
Combustion is a reaction in which an element or compound combines with oxygen to form a simple oxygen-containing compound.
example :
CO2 , H2O and SO2
C3H8 + 5O2 --- 3CO2 + 4H2O
2C6H14O4 + 15O2 --- 12CO2 + 14H2O
B. Merging (Synthetic)
It is a reaction in which a more complex substance is formed of two or more simpler substances (both elements and compounds). Example :
- 2H2 + O2 --- 2H2O
- CO + 2H2 --- CH3OH
C. Decomposition
Decomposition is a reaction in which a substance is broken down into simpler substances.
For example: 2 Ag2O --- 4Ag + O2
D. Replacement
Replacement is a chemical reaction in which an element transfers another element in a compound.
For example: Cu + 2Ag + --- Cu2 + + 2 Ag
E. Metathesis (date transfer)
Metasis is a reaction where there is an exchange between two reactions.
Example:
AgNO3 + NaCl --- AgCl + NaNO3
2. Atom is a small part of an element that still has the same properties with its elements.
3. In chemical reactions, atoms are not destroyed, not created and can not be converted into atoms of other elements.
Chemical reactions are simply rearrangement of the arrangement of atoms involved in the reaction.
The types of chemical reactions, namely:
A. Burning
Combustion is a reaction in which an element or compound combines with oxygen to form a simple oxygen-containing compound.
example :
CO2 , H2O and SO2
C3H8 + 5O2 --- 3CO2 + 4H2O
2C6H14O4 + 15O2 --- 12CO2 + 14H2O
B. Merging (Synthetic)
It is a reaction in which a more complex substance is formed of two or more simpler substances (both elements and compounds). Example :
- 2H2 + O2 --- 2H2O
- CO + 2H2 --- CH3OH
C. Decomposition
Decomposition is a reaction in which a substance is broken down into simpler substances.
For example: 2 Ag2O --- 4Ag + O2
D. Replacement
Replacement is a chemical reaction in which an element transfers another element in a compound.
For example: Cu + 2Ag + --- Cu2 + + 2 Ag
E. Metathesis (date transfer)
Metasis is a reaction where there is an exchange between two reactions.
Example:
AgNO3 + NaCl --- AgCl + NaNO3
Some
examples of chemical reactions
1. The reaction containing the precipitate
A. PbCr2O + K2 (NO3) 2 --- Pb (NO3) 2 + K2Cr 3O7
B. PbOH + Na (NO3) 2 --- Pb (NO3) 2 + Na OH
From the reaction, both produce white precipitate. It is caused by the solution of Pb (NO 3) 2 which is the precipitate of this solution, because Pb (NO 3) 2 has solid properties.
2. Reactions that produce discoloration
A. K2Cr2O7 + NaOH --- K2OH + NaCr207
B. K2Cr2O7 + HCl --- K2Cl + HCr2O7
In K2Cr2O7 solution which initially is orange and NaOH color is white, then after mixing will produce yellow color. Likewise with K2Cr204 solution is yellow, after mixed with white HCl will produce orange color.
3. The reaction that produces gas
Zn + 2 HCl --- ZnCl2 + H2
The gas-generating reaction can occur when the zinc metal plate (Zn) is mixed with HCl solution.
From the above examples, it can be concluded that the chemical reactions can be seen from the changes that occur due to mixing two substances such as sediment formed, discoloration, and produce gas.
The best way to give a chemical reaction is to write a balanced chemical equation, which is a qualitative and quantitative statement of the reactants involved. Each substance is represented by its molecular formula. Express the number of atoms of each kind in units of the substance. Three common classes of reactions are found in chemical reactions, namely:
1. Direct combination reactions
2. Reaction of simple change
3. Record double digits
Chemical reactions change the substances of origin into new substances (products). The changes that occur can be expressed by using the chemical formula of the substances involved in the reaction. This mode of exposure is called the reaction equation. For example, the reaction between hydrogen gas and oxygen gas to form water, is described as follows:
2H2O (g) + O2 (g) --- 2H2O (l)
The arrows indicate the direction of the reaction, read "reacts to". Small letters in parentheses state the form: g means gas, l means liquid (liquid), s means solid (solid), and aq means aqueus (solution in water).
1. The reaction containing the precipitate
A. PbCr2O + K2 (NO3) 2 --- Pb (NO3) 2 + K2Cr 3O7
B. PbOH + Na (NO3) 2 --- Pb (NO3) 2 + Na OH
From the reaction, both produce white precipitate. It is caused by the solution of Pb (NO 3) 2 which is the precipitate of this solution, because Pb (NO 3) 2 has solid properties.
2. Reactions that produce discoloration
A. K2Cr2O7 + NaOH --- K2OH + NaCr207
B. K2Cr2O7 + HCl --- K2Cl + HCr2O7
In K2Cr2O7 solution which initially is orange and NaOH color is white, then after mixing will produce yellow color. Likewise with K2Cr204 solution is yellow, after mixed with white HCl will produce orange color.
3. The reaction that produces gas
Zn + 2 HCl --- ZnCl2 + H2
The gas-generating reaction can occur when the zinc metal plate (Zn) is mixed with HCl solution.
From the above examples, it can be concluded that the chemical reactions can be seen from the changes that occur due to mixing two substances such as sediment formed, discoloration, and produce gas.
The best way to give a chemical reaction is to write a balanced chemical equation, which is a qualitative and quantitative statement of the reactants involved. Each substance is represented by its molecular formula. Express the number of atoms of each kind in units of the substance. Three common classes of reactions are found in chemical reactions, namely:
1. Direct combination reactions
2. Reaction of simple change
3. Record double digits
Chemical reactions change the substances of origin into new substances (products). The changes that occur can be expressed by using the chemical formula of the substances involved in the reaction. This mode of exposure is called the reaction equation. For example, the reaction between hydrogen gas and oxygen gas to form water, is described as follows:
2H2O (g) + O2 (g) --- 2H2O (l)
The arrows indicate the direction of the reaction, read "reacts to". Small letters in parentheses state the form: g means gas, l means liquid (liquid), s means solid (solid), and aq means aqueus (solution in water).
-Causes
of chemical reactions:
1. Occurs due to burning.
2. Occurs due to mixing of substances.
3. Occurs due to the flow of electricity.
In the reaction equation there is a symbol of the form of substance: s (solid), aq (aqueous), l (liquid) and g (gas).
Characteristics of chemical reactions:
A. Making gas
B. Formation of precipitate
C. Discoloration
D. Temperature changes
Various kinds of chemical reactions:
1. Decomposition
2. Oxidation
3. Reduction
4. Neutralization
5. Precipitation
6. Exchange
7. Fermentation
C. Chemical Reactions in Everyday Life
1. Corrosion
2. Decomposition of food
3. Fireworks
1. Occurs due to burning.
2. Occurs due to mixing of substances.
3. Occurs due to the flow of electricity.
In the reaction equation there is a symbol of the form of substance: s (solid), aq (aqueous), l (liquid) and g (gas).
Characteristics of chemical reactions:
A. Making gas
B. Formation of precipitate
C. Discoloration
D. Temperature changes
Various kinds of chemical reactions:
1. Decomposition
2. Oxidation
3. Reduction
4. Neutralization
5. Precipitation
6. Exchange
7. Fermentation
C. Chemical Reactions in Everyday Life
1. Corrosion
2. Decomposition of food
3. Fireworks
There
are many different types of chemical reactions.
Chemists have classified the many different reactions into general
categories. The chemical reactions we
will explore are a representation of the types of reactions found in each
group. There is a general description of
the main reaction types and specific examples provided in the selection boxes.
1. Synthesis
Reaction (Combination Reaction)
In a synthesis
reaction, two or more substances combine to form a new compound. This type of reaction is represented by the
following equation.
A + B 
AB
AB
A and B represent the reacting
elements or compounds while AB represents a compound as the product.
The following examples are
representative of synthesis reactions.
Formation of Aluminum
Bromide: When
Al is placed on the surface of liquid Br2 an exothermic reaction
occurs. The Al is oxidized to Al3+ by the Br2, which is
reduced to Br - ions.
The ionic product, AlBr3, can be observed on the watch glass after
the reaction.
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Formation of Sodium
Chloride: Molten
sodium burns when it is put into a container of chlorine gas. In the reaction
a sodium ion loses an electron to form a sodium cation and a chlorine atom
simultaneously gains an electron to form a chloride anion. The product of the
reaction is the ionic compound sodium chloride, which is the white solid
observed.
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Formation of Zinc
Oxide: Oxidation
is a loss of electrons and reduction is a gain of electrons. The oxidation of
metallic Zn by O2 to form ZnO(s) is illustrated at the
molecular level. The transfer of electrons from Zn to O2 is shown.
Atoms can be observed to change as they are oxidized or reduced, respectively
to their ionic forms.
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Formation of Sodium
Hydroxide and Potassium Hydroxide: When
a small piece of Na is added to a solution containing an indicator, evidence
of the reaction can be observed by the change in the color of the solution as
NaOH is formed, by the melting of the Na and by the movement of the Na caused
by formation of hydrogen gas. K is more reactive than Na as demonstrated by
its reaction with water. This reaction produces enough heat to ignite the H2
produced.
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2. Single-Replacement Reaction
In a single-replacement reaction
(displacement reaction) one element replaces a similar element in the compound. Single-replacement reactions can be
represented by the following equations.
AB + C AC + B
AC + B|
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Thermite
Reaction: In
the thermite reaction, Al reduces Fe2O3 to Fe in an
extremely exothermic reaction in which Al is oxidized to Al2O3.
The reaction produces enough heat to melt the iron. Because of the extreme
heat produced in the thermite reaction, it is used industrially to weld iron.
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Reduction of
CuO: When
black carbon and black copper oxide are heated together the Cu2+
ions are reduced to metallic Cu and a gas is evolved. When the gas is
collected in Ca(OH)2 a white precipitate of CaCO3 is
formed. The reaction which occurs involves the reduction of Cu2+
ions by carbon which is oxidized to CO2.
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Formation of Silver
Crystals: When
a copper wire is placed in a solution of AgNO3, the Cu reduces Ag+
to metallic Ag. At the same time, Cu is oxidized to Cu2+. As
the reaction progresses Ag crystals can be seen to form on the Cu wire and
the solution becomes blue as a result of the formation of Cu2+
ions.
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Formation of Tin
Crystals: Oxidation-reduction
chemistry of Sn and Zn. When acidified Sn(II)Cl2 is added to a
beaker containing a piece of Zn, some of the Sn2+ reacts with H+
in the solution to produce H2 gas. Immediate changes can also be
observed on the surface of the Zn as it quickly becomes coated with Sn
crystals. After the reaction has progressed for a time needles of Sn can be
observed on the surface of the Zn.
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3. Double-Replacement
Reaction
In
a double-replacement reaction, the ions of two compounds exchange places in an
aqueous solution to form two new
compounds. A double-replacement
reaction can be represented by the following equation.
AB + CDAC + BD
AC + BD |
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This marble statue
has been eroded by acid rain. Marble is a material having CaCO3 as
its primary component. Acids react with and dissolve the marble. The acid comes from sulfur dioxide in the
atmosphere combining with water to form sulfurous acid.
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An aqueous solution
of Potassium Iodide is added to an aqueous solution of Lead (II) Nitrate
forming lead (II) iodide. The formation
of a precipitate occurs when the cations of one reactant combines with the
anions of the other reactant to form an insoluble or slightly insoluble
compound.
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An aqueous solution
of Sodium Chloride is added to an aqueous solution of Silver Nitrate forming
silver chloride.
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4. Decomposition
Reaction
In
a decomposition reaction, single compound undergoes a reaction that produces
two or more simpler
substances. A decomposition reaction can be
represented by the following equation.
AB A + B
A + B
Electrolysis of
Water: When a
direct current is passed through water it decomposes to form oxygen and
hydrogen. The volume of hydrogen gas produced at the negative electrode is
twice the volume of the oxygen gas formed at the positive electrode. This
indicates that water contains twice as many hydrogen atoms as oxygen atoms,
which is an illustration of the law of constant composition.
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Decomposition
of Nitrogen Triiodide: Nitrogen triiodide is extremely
unstable when it is dry. Touching it with a feather causes it to decompose
explosively. The explosion occurs as chemical energy is released by the
decomposition of nitrogen triiodide to N2 and I2.
Violet iodine vapor can be observed after the explosion.
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5. Combustion Reaction
In
a combustion reaction, a substance combines with oxygen, releasing a large
amount of energy in the form of light and
heat. For organic compounds, such as
hydrocarbons, the products of the combustion reaction are carbon dioxide and
water.
CH4 + 2
O2 
CO2 + 2
H2O
CO2 + 2
H2O|
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The combustion of
hydrogen yields water vapor as a reaction product. Three balloons of hydrogen and one balloon
mixed with hydrogen and oxygen form an explosive mixture
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Reactions with
Oxygen. Magnesium, steel wool, white phosphorous, and sulfur are burned in
oxygen. The resulting reactions are combination reactions in which two
substances react to form one product. The products formed in these reactions
are MgO, Fe2O3, P4O10 and SO2.
All of these combustion reactions are very exothermic.
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The combustion of
yellow phosphorus occurs in an oxygen atmosphere. The main product of
this reaction is phosphorus pentoxide.
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Http://www.erfolgkimia.com/2015/07/perchange-materi-dan-reaksi-kimia.html
(Access 21 april 2017)
Http://reizacullen777.blogspot.co.id/2012/11/reaiksi-kimia-tidak-menyebabkan.html
( access 21 april 2017 )
http://www.ric.edu/faculty/ptiskus/reactions/
(Access 21 april 2017)
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