Chemical Reactions Summary
General Reaction Types
Combustion Reactions:
Combustion is a chemical reaction in which a fuel reacts with oxygen to release energy in the form of heat and light.
FUEL + OXYGEN à CARBON DIOXIDE + WATER + ENERGY
Complete combustion needs a plentiful supply of air so that the elements in the fuel react fully with oxygen.
In general for complete combustion:
hydrocarbon + oxygen → carbon dioxide + water
Incomplete combustion occurs when the supply of air or oxygen is poor. Water is still produced, but carbon monoxide and
carbon are produced instead of carbon dioxide.
In general for incomplete combustion:
hydrocarbon + oxygen → carbon monoxide + carbon + water
Good signs that you are dealing with a combustion reaction include the presence of oxygen as a reactant and carbon dioxide,
water and heat as products.
Synthesis Reactions:
A synthesis reaction is a type of reaction in which multiple reactants combine to form a single product. Synthesis reactions
release energy in the form of heat and light and therefore are exothermic reactions.
Simple chemical (A) + Simple Chemical (B) à Complex Chemical (AB)
Example: Mg + 2Cl à MgCl2
Decomposition Reactions:
Elements are pure substances that cannot be broken down. One way to distinguish an element from a compound is to see if it
will break down into simpler substances.
This type of reaction is called a DECOMPOSITION REACTION
A decomposition reaction is a type of chemical reaction in which a single compound breaks down into simpler or smaller parts;
however we cannot break it any smaller than the elements that it is made of. To do this we need energy to break the bonds
holding the compounds together and therefore require an energy source such as heat, light or electricity.
Complex Chemical (XY) à Simple chemical (X) + Simple Chemical (Y)
Example: CuCO3 (s) à CuO (s) + CO2 (g)
Precipitation Reactions:
Precipitation reactions involve two solutions reacting to form an insoluble product (solid), the precipitate. Most precipitation
reactions involve ions from one solution reacting with ions from another solution.
In a precipitation reaction, ions collide with one another to form an insoluble product (one that does not dissolve in water). This
is the precipitate.
Soluble solution A + soluble solution B à Insoluble solid C + soluble solution D
CuSO4(aq) + 2NaOH(aq) → Na2SO4(aq) + Cu(OH)2(s)
Neutralisation Reactions:
A neutralisation reaction is when an acid and a base react to form water and a salt and
involves the combination of H+ ions and OH- ions to generate water.
Acid + Base à Salt + Water
Example: H2SO4 + 2KOH à K2SO4 + 2H2O
Reactions of Acids with Carbonates:
When acids react with carbonates, such as calcium carbonate, a salt, water and carbon dioxide it produced. Notice
that an extra product, carbon dioxide is produced. It causes bubbling during the reaction and can be detected using
limewater.
Acid + Carbonate à Salt + Carbon Dioxide + Water
Example: 2HCl + CaCO3 à CaCl2 + CO2 + H2O
HINT: If there is carbon somewhere in the reactant side then most likely going to be a acid + carbonate reaction!
Reactions of Acids with Metals:
Acids will react with reactive metals, such as magnesium and zinc to produce a salt and hydrogen. The hydrogen
causes bubbling during the reaction and can be detected using the ‘pop test’ using a lighted splint.
Acid + Metal à Salt + Hydrogen gas
Example: 2HCl + Mg à MgCl2 + H2
NOTE: The salt that is produced depends upon which acid and which metal react.
https://www.youtube.com/watch?v=4uqlaVTKy4U
EXTRA: Which salt is formed?
When an acid reacts with a metal, metal oxide, metal hydroxide or metal carbonate, a salt is made. The name of the salt can be
easily worked out.
The first part of the name comes from the metal, or the metal in the oxide, hydroxide or carbonate.
The second part of the name comes from the acid used:
Ø Sulfuric acid produces salts called sulfates
Ø Hydrochloric acid produces salts called chlorides
Ø Nitric acid produces salts called nitrates