Chemical reactions are occurring around us all the time
–Food cooking –Fuel being burned in a car’s engine –Oxygen being used in the human body
To describe the reaction that creates fire at the bunsen burner in lab:
Methane gas reacts quickly with oxygen gas to produce fire, carbon dioxide, and water vapor
That’s a lot to write!
We can simplify the description of our reaction by using a word equation:
Methane gas + oxygen gas →fire + carbon dioxide gas + water vapor
Still a lot to write!
The simpler way to express a chemical reaction is to use formula equations:
CH4 + O2 → CO2 + H2O
However there is some information that is not shown in the formula equation:
– State of matter – Fire/ Energy
We can show state of matter using the following symbols:
(s) solid(l) liquid(g) gas(aq) aqueous solution
(substance is dissolved in water)
CH4 (g)+ O2 (g) → CO2 (g) + H2O (g) + energy
Is the equation balanced?
CH4 (g)+ O2 (g) → CO2 (g) + H2O (g) + energy
CH4 (g)+ 2O2 (g) → CO2 (g) + 2H2O(g) + energy
Practice writing these equations:
Hydrogen plus oxygen yields waterH2 + O2 → H2 O
Nitrogen plus hydrogen yields ammoniaN2 + H2 → NH3
Aluminum bromide plus chlorine yields aluminum chloride and bromine
AlBr3 + Cl2 → AlCl3 + Br2
Balance and include state of matter:
2H2 (g) + O2(g) → 2H2 O(l)
N2 (g) + 3H2(g) → 2NH3(g)
2AlBr3(s) + 3Cl2(g) → 2AlCl3(s) + 3 Br2(l)
Nitrogen plus oxygen gas react and form dinitrogen pentoxide
2N2(g) + 5O2 (g) → 2N2 O5 (g)
There are five general types of reactions: Synthesis Decomposition Single-replacement Double-replacement Combustion
Decomposition Reaction
A reaction where a compound breaks down into two or more simpler products
Single Replacement Reaction
A single-replacement reaction is one in which one element replaces a second element in a
compound
Double Replacement Reaction
AB + CD = AD + CBA double-replacement reaction is a reaction
involving an exchange of positive ions between two compounds
Combustion Reaction
CH4 + 2O2 → CO2 + 2H2O + energy
• A combustion reaction is a reaction in which an element or a compound reacts with oxygen, to form an oxide and heat
• Hydrocarbons combust with oxygen to form carbon dioxide and water.