Types of Chemical Reactions
5 types of reactions
Summary
• Today you will perform experiments that
include each of the major types of chemical
reaction
• These are
– single replacement
– double displacement
– combustion
– decomposition
– combustion
Single Replacement
• In this type of reaction an element in a
compound is replaced by another
Ca + ZnSO4  Zn + CaSO4
Cl2 + 2NaBr  Br2 + 2NaCl
Double Replacement
• Two ionics swap partners ….
CaCl2 + ZnSO4  CaSO4 + ZnCl2
Combination Reaction
• This happens when 2 substances become 1
substance
Ca + Cl2  CaCl2
• Or when 2 compounds make a larger
compound
CaO + H2O  Ca(OH)2
Decomposition Reaction
• This is the opposite of a combination reaction
it is when a substance falls apart into other
substances
Ca(OH)2  CaO + H2O
Combustion Reaction
• AKA burning, when a substance combines
with oxygen
CH4 + 2O2  CO2 + 2H2O
• Often water and carbon dioxide are produced
Oxidation-Reduction Reactions
• Some of the 5 types of reaction can be classified of
Reduction-Oxidation (Redox) reactions
• Something loses electrons (is oxidized)
• And something receives the electrons (is reduced)
• All single replacement reactions are redox reactions
Ca + ZnSO4  Zn + CaSO4
Ca + (Zn2+)(SO42-)  Zn + (Ca2+)(SO42-)
Ca  Ca2+ + 2e-
Zn2+ + 2e-  Zn
Ca loses electrons and is oxidized to Ca2+ Zn2+ gains electrons and is oxidized to Zn
Oxidation-Reduction Reactions
• All combustion reactions are redox reactions
• Its harder to see because the elements don’t have
charges to help us see
• Oxidation is the gain of oxygen (or loss of H)
• Reduction is the loss of oxygen (or gain of H)
CH4 + 2O2  CO2 + 2H2O
C in CH4 gains O it is oxidized
O in H2O has gain H and has been reduced, or
the O2 has lost O and is reduced
Evidence of a Chemical Reaction
• Reactions in this experiment are conducted in
water (solvent)
• Here are indicators that a reaction has
occurred
– Formation of a Gas
– A Precipitate Forms
– Heat is Produced
– A Color Change in Seen (unreliable)
Balancing Reactions
• Three Rules to Balancing Equations
1. Write correct Formulae of reactants and
products
2. Use Stoichiometric coefficients in front of each
compound so that the number of atoms of each
type on the left hand side are the same as on the
right
3. Use the smallest whole numbers possible as
coefficients
The Reactions
• 1 mL 0.1 M CaCl2 + 1 mL 0.1 M Na3PO4
• Heat 0.5 g of table sugar in a disposable test tube
over a bunsen
– what is the liquid forming on the side of the test tube?
• 3 mL H2O2 and a spatula tip of MnO2 and heat
– a gas is evolved O2 – you can prove by adding a
glowing splint
• 3 mL of 3 M HCl and a small piece of Zinc
– after about 30 s bring a lighted splint to the mouth of
the tube
The Reactions
• 1 mL 3M HCl + 1 mL 1.0 M Na2CO3
– what is the gas? Place a lighted splint in the test tube
• 2 mL 3M H2SO4 in a test tube with 2 drops of
phenolphthalein then add 5 mL of 3M NaOH
– color changes? phenolphthalein is pink when the
water is alkaline and clear when acid
– Feel the bottom of the tube is the reaction mixture
warm
• 2mL of 0.05 M AgNO3 and a small piece of Cu in a
test tube
– Careful AgNO3 causes chemical burns to clothes and
skin
• 0.5 g CuSO4.H2O and heat in a test tube