Download combination with O 2

Mass Relationships in
Chemical Reactions
Chapter 3
C
S
Hg
Cu
Fe
2Li + 2H2O → 2LiOH + H2
Example of where we’re going in this chapter...
How many grams of calcium chloride can be
produced from 5.0750 g of calcium?
Ca (s) + Cl2 (g) → CaCl2 (s)
 1 mole Ca  1 mol CaCl2

5.0750 g Ca
 40.078 g Ca  1 mol Ca
 110.98 g CaCl2

 1 mol CaCl2

 

14.054 g CaCl2
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)
Reactants
→
CO2 (g) + 2 H2O (g)
→
Products
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!
Subscripts and Coefficients Give Different Information
• Subscripts – give the number of atoms of
each element in a molecule
• Coefficients - give the number of molecules
Cu +
HCl →
CuCl2 +
H2
Cu + 2 HCl →
CuCl2 +
H2
Na + H2O → NaOH + H2
2 Na + 2 H2O → 2 NaOH + H2
Patterns of Chemical Reactivity
• Combination
• Decomposition
• Combustion in Air (combination with O2)
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)
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
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)