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Types Of Chemical Reaction
The collage is in form of star containg eight petals
Three petals of star show
Indicator of chemical reaction
1.Formation of precipitate
2. Colour change
3. Emission of odor
All chemical Reactions have two parts
1. Reactants- the substance s you start with
2. Products- the substances you end up with
3. The reactants turn into the products
4. Reactants-à Products
Types Of Chemical Reactions
To react or not to react?
That is the question
Chemical changes are result of chemical reactions.
All chemical reactions involve a change in substances and a change in energy.
Neither matter nor energy is created or destroyed in chemical reaction-only changed
Five petals of star collage show different five types of reaction
1.Synthesis Reaction
Synthesis Reaction are also called combination reaction
In synthesis reaction two or more simple substance combine to form a more complex substance as shown in cartoon below.
The cartoon below also show a synthesis reaction : the thin bird(reactant) and the worm(Reactant) combine to make one product , a big fat bird.
In Synthesis Reaction
Two elements or compounds combine to make one compound
The reaction through the equation is written below
Reactant + Reactant à Products
A + B à AB
For example, simple hydrogen gas combined with simple oxygen gas can produce a more complex substance ----- water
The chemical equation for this synthesis reaction is : 2H2(g) + O2(g) → 2H2O
Some Types of Synthesis Reaction
Metal + Oxygen → metal oxide
4Fe (s) + 3O2 →2 Fe 2O3(s)
Nonmetal + oxygen → non metal oxide
S(s) + O2(g) →SO2(g)
2. Decomposition Reaction
Decompose =fall apart, one compound reactant fall apart into two or more elements or compounds,usually requires energy
In a decomposition reaction a more complex substance breaks down into its more simple parts.
AB -------> A + B
One reactant yields 2 or more products. Basically, synthesis and decomposition reactions are opposites. reactant -------> product + product
The cartoon below shows Decomposition reaction
The cartoon below shows ,the egg (the reactant), which contained the turtle at one time, now has opened and the turtle (product) and egg shell (product) are now two separate substances.
Some Types of Decomposition Reaction
Decomposition of sodium chloride: On passing electricity through molten sodium chloride, it decomposes into sodium and chlorine.
Electricity
2NaCl----------------à 2Na + Cl2(g) ↑
Metallic carbonates, when heated, form metallic oxides and CO 2(g).
CaCO 3(s) ® CaO (s) + CO 2(g).
Most metallic hydroxides, when heated, decompose into metal oxides and water.
Ca(OH) 2(s) ® CaO (s) + H 2 O (g).
Some oxides, when heated, decompose.
2HgO (s) ® 2Hg (l) + O 2(g) ↑
Some acids, when heated, decompose into nonmetallic oxides and water.
H 2 SO 4(s) ® H 2 O (l) + SO 3(g) ↑
3.A single Replacement Reaction
In a single replacement reaction a single uncombined element replaces another in a compound. Also refered to as single displacement,one element replaces another
Reactant must be element and compound
Product will be different element and different compound
Two reactants yield two products.
Reactant + Reactant ---------> Product + Product
AB + C -------> AC + B
AB=Compound, C= Element; AC=Different Compound, B=Different Element
In figure below the boy in the orange shirt steals the date of the other boy. So, a part of one of the reactants change places and is in a different place among the products.
Replacement of a metal in a compound by a more active metal.
Fe (s) + CuSO 4(aq) ® + FeSO 4(aq) + Cu (s)
Some Types of Single Displacement Method
For example when zinc combines with hydrochloric acid, the zinc replaces hydrogen.
The chemical equation for this single replacement reaction looks like:
Zn + 2HCl ® ZnCl 2 + H 2(g) ↑
Replacement of nonmetal by a more active nonmetal.
Cl 2(g) + 2NaBr (aq) ® 2NaCl (aq) + Br 2(g)↑
Replacement of hydrogen in water by an active metal.
Mg (s) + H 2 O (aq) ® MgO(aq) + H 2(g) ↑
4.Double Replacement Reaction
Two things replace each other .
Two things replace each other. reactants must be two ionic compound or acids, usually in aqueous solution
The figure below shows the double replacement reaction.
In cartoon below reactant A has -----coloured cap ,while B has-----coloured ,therefore product C is , face of A with cap of B. Similarly product D is face of B with cap of A.
For example when silver nitrate combines with sodium chloride, two new compounds--silver chloride and sodium nitrate are formed because the sodium and silver switched places.
The chemical equation for this double replacement reaction looks like:
AgNO 3 + NaCl ® AgCl ↓+ NaNO 3
5.Combustion
A reaction in which a compound (often carbon) reacts with oxygen to give out CO2 and H2O as products.
CH4 +2O2 à CO2 + 2H2O
C3H8+ 5O2 à 3CO2 +4H2O
C6H12O6 +6 O2 à 6CO2 + 6H2O
How to Recognise which type is your reaction
Look at the reactants
Element (E)
Compound ( C)
E +E Synthesis
C Decomposition
E+ C Single Replacement
C+C Double Replacement
Look at the products
Combustion
CO2 + H2O
Message :
Collage “Types Of Chemical Reactions “ is shown in shape of star ,which is a symbol, showing that if a student has good knowledge regarding the types of reaction ,he/she is going to be rock star of the scientific world .
References
http://utahscience.oremjr.alpine.k12.ut.us/sciber99/8th/matter/sciber/chemtype.htm
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