Chemical Equations

1
Chemical Equations

• Section 24.2

2
Balancing Equations

• H2(g) O2(g) ? H2O (l)
• 2 oxygen atoms on reactant side but only 1 on
  product side
• Does not obey law of conservation of mass-
  appears one O is destroyed
• H2(g) O2(g) ? H2O2 (l)
• Not a good solution- changed what the equation
  said- no longer forms water
• Now it forms hydrogen peroxide

3
Balancing Equations

• Do not change subscripts- it changes identity of
  the compound
• The equation represents the formation of a
  different compound
• Balancing equation equation which has the same
  number of atoms of each element on both sides of
  the equation.
• involves changing ONLY the coefficients in an
  equation

4
Balancing Equations

• How to balance equations
• Choose coefficients so that the number of atoms
  of each element is the same on both sides
• Do oxygen last
• Trial and error

5
Steps to Balancing Equations

• 1. Write a chemical equation for the reaction
  using formulas and symbols.
• 2. Check the equation for atom balance.
• 3. Choose coefficients that balance the
  equation. NEVER change subscripts. ONLY change
  coefficients.
• 4. Recheck the numbers of atoms for each element