1. Mass Relationships in Chemical Reactions
Chapter 3 C S Hg Fe Cu
2Li + 2H2O → 2LiOH + H2

2. How many grams of calcium chloride can be
Example of where we’re going in this chapter...
How many grams of calcium chloride can be
produced from g of calcium?
Ca (s) + Cl2 (g) → CaCl2 (s)

3. CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g)
A process in which one or more substances is changed into one or more new substances is a chemical reaction
Chemical equation - use of chemical symbols to show what happens during a chemical reaction
The reaction between methane and oxygen
to produce carbon dioxide and water:
CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g)
Reactants → Products

4. CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g)
Info in a Chemical Equation
CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g)
States of the reactants and products are written in parentheses to the right of each compound.
Coefficients are inserted to balance the equation.
Coefficients NEVER represent mass!

5. Subscripts and Coefficients Give Different Information
Subscripts – give the number of atoms of each element in a molecule
Coefficients - give the number of molecules

6. Cu HCl → CuCl H2
Cu HCl → CuCl H2
Na + H2O → NaOH + H2
2 Na H2O → 2 NaOH + H2

7. Patterns of Chemical Reactivity
Combination
Decomposition
Combustion in Air (combination with O2)

8. Combination Reactions
Two or more substances react to form one product
2 Mg (s) + O2 (g)  2 MgO (s)
N2 (g) + 3 H2 (g)  2 NH3 (g)
C3H6 (g) + Br2 (l)  C3H6Br2 (l)

9. Decomposition Reactions
One substance breaks down into two or more substances.
CaCO3 (s)  CaO (s) + CO2 (g)
2 KClO3 (s)  2 KCl (s) + O2 (g)
2 NaN3 (s)  2 Na (s) + 3 N2 (g)
~ 100g
~ 50L

10. Combustion Reactions Generally rapid reactions that produce a flame
Most often involve hydrocarbons reacting with oxygen in the air
CH4 (g) + 2 O2 (g)  CO2 (g) + 2 H2O (g)
C3H8 (g) + 5 O2 (g)  3 CO2 (g) + 4 H2O (g)