Describing Chemical
Reactions
Ch. 6
What are chemical equations
• Chemical equations use chemical
formulas and other symbols instead of
words to summarize a reaction.
Formulas in the equation
• All chemical equations use formulas to
represent substances involved in a
reaction.
• Ex. CO2 is a formula for carbon dioxide.
Structure of an equation
• Reactants ----> products
• The number of reactants and products
can vary.
• CaCO3 ------> CaO + CO2
Conservation of Mass
• Matter is not created or destroyed.
• The principal of conservations of mass
states that in a chemical reaction, the
total mass of the reactants must equal
the total mass of the products. (the
same on each side)
Steps for balancing equations
•
•
•
•
1. Write the equation
2. Count the atoms
3. Use coefficients to balance atoms
4. Look back and check
• H2 + O2 -----> H2O
Balance the equations
• Fe2O3 + C ----> Fe + CO2
• SO2 + O2 ----> SO3
• Fe + HCL ---> FeCl2 + H2
• N2 + O2 ----> N2O3
• MgO + HBr ----> MgBr2 + H2O