1. Chapter 8 Chemical Equations !
Word Equation – the names of the substances are given in
words for you to interpret.
Zinc plus Hydrochloric Acid yields Zinc chloride plus Hydrogen gas !
REACTANTS PRODUCTS

2. Interpreting chemical equations
Al (OH)3 + 3HCl AlCl3 + 3 H2O
Reacts To make And three
One
with 3 one FU of molecules
formula
molecules aluminum of water
unit of
of HCl chloride
aluminum
hydroxide
SO WHAT DOES THIS MEAN????

3. Balanced Equations
2Na + 2H2O  2NaOH + H2
Because mass is neither lost nor gained in a chemical
reaction, all atoms of both substances must be
accounted for.

4. Steps For Balancing
Chemical Equations
1. Write a word equation for the reaction
2. Write the correct formula for all the reactants and products
3. Determine coefficients that make the equation balance
ONLY CHANGE COEFFICIENTS, NEVER EVER
CHANGE THE SUBSCRIPTS !!!!!!!!!!!!!!!!!!!!

5. Showing Energy
Endothermic Reactions
2H2O + Energy  2H2 + O2
Exothermic Reactions
2H2 + O2  2H2O + Energy

6. Showing Phases in
Chemical Reactions
Substances may exist in the form of a solid liquid or gas
Solid Phase: Definite volume and shape.
Liquid Phase: Definite volume, but changes shape.
Gaseous Phase: No definite volume or shape.
Use a (s) for solid, (l) for liquid, (g) for gas and (aq) for
aqueous solutions. Remember, aqueous means dissolved in
a solution (usually water !)

7. Ions in water solution
When ionic substances dissolve in water their crystal lattice
structure breaks up and they exist as IONS in water !
NaCl yields Na + plus Cl -
KCl yields K+ plus Cl-

8. Classifying chemical reactions
Synthesis reaction A + B yields AB
IRON PLUS OXYGEN yields IRON (111) OXIDE
Decomposition reaction AB yields A + B
Single Replacement A + BC yields B plus AC
Zinc + HCl yields Zinc Chloride + Hydrogen gas
Double Replacement AB plus CD yields AD plus CB
NaOH + Magnesium chloride yields ????????????

9. Tricks to remember
In single replacement reactions the “thing” that is ALONE
must be more REACTIVE than the “thing” being replaced or
no reaction will occur !! (see page 286)
In double replacement reactions you must have a
PRECIPITATE, GAS, OR WATER AS A PRODUCT IN
ORDER FOR THE REACTION TO OCCUR !! (otherwise all
reactants are water soluble.)

10. Ionic equations and spectators !
• Ionic equations simply show what is
happening to the ions taking part in a
reaction.
• Spectator ions are those which do not
actually participate in the reaction.
• See rules page 224 !

11. Predict the products of the reaction.
Zinc + copper sulfate yields Zinc sulfate + copper
Magnesium chloride plus NO REACTION!
Iron yields
Calcium chloride + Sodium Calcium carbonate
carbonate yields precipitate + NaCl

12. Predict the products
Fluorine + NaI Iodine + NaF
Hydrogen + Oxygen WATER
KClO3 KCl + Oxygen
CH O + O Carbon dioxide +
6 12 6 2
water

13. Write the NET ionic equation which
occurs when aqueous solutions of
zinc chloride and potassium
hydroxide react.
ZnCl2 (aq) + 2 KOH (aq) Zn (OH)2(s) + 2 KCl(aq)
Zn+2 + 2Cl-1 + 2K+ + 2OH- Zn(OH)2(s) + 2K+ + 2Cl-
Zn+2 + 2OH- Zn(OH)2(s)

14. Predict the products
When K reacts with MgF 2 Mg + KF
When Mg reacts with KF NO REACTION

15. Predict the products
NaOH + KCl
NaNO3+ KBr
Ammonium Carbonate + Magnesium carbonate as
precipitate and
Magnesium Chloride
ammonium ions and
chloride ions as
spectators

16. soluble
DOUBLE REPLACMENT
Terminology…. aqueous
PRECIPITATE
SPECTATOR ION
COMBUSTION
SINGLE REPLACEMENT DECOMPOSITION
COEFFICIENT Net ionic equation
SYNTHESIS
REACTION Activity series