Types of Chemical Reactions
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Transcript of Types of Chemical Reactions
Types of Chemical Reactions
Writing Chemical Reactions
Types of Reactions Many chemical
reactions have defining characteristics which allow them to be classified as to type.
Types of Chemical Reactions
The five types of chemical reactions in this unit are: Combination Decomposition Single Replacement Double Replacement Combustion
Combination Reactions Two or more substances combine to
form one substance. The general form is A + X AX
Example: Magnesium + oxygen
magnesium oxide 2Mg + O2 2MgO
Combination Reactions Combination reactions may also be
called composition or synthesis reactions.
Some types of combination reactions: Combination of elements
K + Cl2 One product will be formed
Combination Reactions K + Cl2
Write the ions: K+ Cl-
Balance the charges: KCl
Balance the equation: 2K + Cl2 2KCl
Combination Reactions Some types of combination
reactions:Oxide + water
Nonmetal oxide + water acidSO2 + H2O H2SO3
Metal oxide + water baseBaO + H2O Ba(OH)2
Combination Reactions Some types of combination
reactions:Metal oxides + nonmetal oxidesNa2O + CO2 Na2CO3CaO + SO2 CaSO3
Predicting products for synthesis reaction
• Write down the reactants that are involved in the reactions on the reactant sideof the equations.
• Knowing that a synthesis reaction is going to occur, put the reactants togetheron the product side of the equation.
• When elements make compounds remember that there is a certin ratiowhich they must combine in. YOU MUST REMEMBER HOW TO WRITE CHEMICAL FORMULAS.
Lets continue looking at the potassium and chlorine reaction.
Combination Reactions K + Cl2
Write down the formula for potassium chloride. KCl
Notice you are missing a Cl atom on the product side. Where did that Chlorine atom go?
No where Balance the equation: 2K + Cl2 2KCl
One more thing to remember when writing equations
Diatomic elements• Elements that never travel alone.
Last example of potassium and chlorineReactants K + Cl2Product KCl
Notice the Chlorine is never by itself this is a diatomic element
How do you remember the diatomic elements?
H.O.Br.F.I.N.ClH – hydrogenO – oxygenBr – BromineF – FluorineI – IodineN – NitrogenCl - Chlorine
PracticePredict the following products.Write a balanced chemical equation for each of the following
Copper + oxygen
Silver + Sulphur
Iron + Oxygen
2Cu + O2 2CuO
2Ag + S Ag2S
3Fe + O2 Fe3O2
Decomposition Reactions
One substance reacts to form two or more substances. The general form is AX A + X
Example: Water can be decomposed by
electrolysis. 2H2O 2H2 + O2
Decomposition Reactions
Types of Decomposition Reactions: Decomposition of carbonates
When heated, some carbonates break down to form an oxide and carbon dioxide.
CaCO3 CaO + CO2H2CO3 H2O + CO2
Decomposition Reactions
Types of decomposition reactions: Some metal hydroxides
decompose into oxides and water when heated.Ca(OH)2 CaO + H2O
Note that this is the reverse of a similar combination reaction.
Decomposition Reactions
Types of decomposition reactions: Metal chlorates decompose into
chlorides and oxygen when heated.2KClO3 2KCl + 3O2Zn(ClO3)2 ZnCl2 + 3O2
Some of these reactions are used in explosives.
Decomposition Reactions
Some substances can easily decompose: Ammonium hydroxide is actually
ammonia gas dissolved in water.NH4OH NH3 + H2O
Some acids decompose into water and an oxide.H2SO3 H2O + SO2
Summary synthesis V.s Decomposition Synthesis
• Non-metal oxide + H2O AcidCO2 + H2O HCO3
• Metal oxide + water Base BaO + H2O Ba(OH)2
• Metal oxide + non-metal oxide polyatomic compound
CaO + SO2 CaSO3Decomposition
• Acid decomposition HCO3 CO2 + H20
• Hydroxide decompositionBa(OH)2 BaO + H2O
• Polyatomic compound decompositionCaSO3 CaO + SO2
Decomposition Reactions
Some decomposition reactions are difficult to predict.
The decomposition of nitrogen triiodide, NI3, is an example of an interesting decomposition reaction.
Single Replacement Reactions
A metal will replace a metal ion in a compound. The general form is A + BX AX +
B
A nonmetal will replace a nonmetal ion in a compound. The general form is Y + BX BY +
X
Single Replacement Reactions
Examples: Ni + AgNO3
Nickel replaces the metallic ion Ag+. The silver becomes free silver and the
nickel becomes the nickel(II) ion. Ni + AgNO3 Ag + Ni(NO3)2
Balance the equation: Ni + 2AgNO3 2Ag + Ni(NO3)
Single Replacement Reactions
Not all single replacement reactions that can be written actually happen.
The metal must be more active than the metal ion.
Aluminum is more active than iron in Al + Fe2O3 in the following reaction:
Thermite Reaction
Thermite Reaction Al + Fe2O3 Aluminum will replace iron(III) as
was seen in the video. Iron (III) becomes Fe and
aluminum metal becomes Al3+. 2Al + Fe2O3 2Fe + Al2O3
Single Replacement Reactions
An active nonmetal can replace a less active nonmetal.The halogen (F2, Cl2, Br2, I2) reactions are good examples.
F2 is the most active and I2 is the least.Cl2 +2 NaI 2 NaCl + I2
Double Replacement Reactions
Ions of two compounds exchange places with each other.The general form is AX + BY AY + BX
Metathesis is an alternate name for double replacement reactions.
Double Replacement NaOH + CuSO4 The Na+ and Cu2+ switch places. Na+ combines with SO4
2- to form Na2SO4.
Cu2+ combines with OH- to form Cu(OH)2
NaOH + CuSO4 Na2SO4 + Cu(OH)2 2NaOH + CuSO4 Na2SO4 + Cu(OH)2
Double Replacement CuSO4 + Na2CO3 Cu2+ combines with CO3
2- to form CuCO3.
Na+ combines with SO42- to form
Na2SO4. CuSO4 + Na2CO3 CuCO3 +
Na2SO4
Double Replacement Na2CO3 + HCl Na+ combines with Cl- to form
NaCl. H+ combines with CO3
2- to form H2CO3.
Na2CO3 + 2HCl 2NaCl + H2CO3 H2CO3 breaks up into H2O and
CO2.
Double Replacement The gas formed was carbon
dioxide. The final balanced reaction is:
Na2CO3 + HCl NaCl + H2O + CO2.
Balance the equation. Na2CO3 + 2HCl 2NaCl + H2O +
CO2
Combustion Reaction When a substance combines with
oxygen, a combustion reaction results.
The combustion reaction may also be an example of an earlier type such as 2Mg + O2 2MgO.
The combustion reaction may be burning of a fuel.
Combustion Reaction Methane, CH4, is natural gas. When hydrocarbon compounds
are burned in oxygen, the products are water and carbon dioxide.
CH4 + O2 CO2 + H2O CH4 + 2O2 CO2 + 2H2O
Combustion Reactions Combustion reactions involve
light and heat energy released. Natural gas, propane, gasoline,
etc. are burned to produce heat energy.
Most of these organic reactions produce water and carbon dioxide.
Practice Classify each of the following as
to type:
H2 + Cl2 2HCl Combination
Ca + 2H2O Ca(OH)2 + H2 Single replacement
Practice 2CO + O2 2CO2
Combination and combustion
2KClO3 2KCl + 3O2 Decomposition
Practice FeS + 2HCl FeCl2 + H2S
Double replacement
Zn + HCl ? Single replacement Zn + 2HCl ZnCl2 + H2