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

Interpreting chemical equations

Al (OH)3 + 3HCl AlCl3 + 3 H2O

SO WHAT DOES THIS MEAN????

One formula unit of aluminum hydroxide

Reacts with 3 molecules of HCl

To make one FU of aluminum chloride

And three molecules of water

Balanced Equations

Because mass is neither lost nor gained in a chemical reaction, all atoms of both substances must be accounted for.

2Na + 2H2O 2NaOH + H2

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 !!!!!!!!!!!!!!!!!!!!

Showing Energy

Endothermic Reactions

2H2O + Energy 2H2 + O2

Exothermic Reactions

2H2 + O2 2H2O + Energy

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 !)

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-

Classifying chemical reactionsSynthesis 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 ????????????

Tricks to rememberIn 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.)

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 !

Predict the products of the reaction.

Zinc + copper sulfate yields Zinc sulfate + copper

Magnesium chloride plus Iron yields

NO REACTION!

Calcium chloride + Sodium carbonate yields

Calcium carbonate precipitate + NaCl

Predict the products

Fluorine + NaI Iodine + NaF

Hydrogen + Oxygen WATER

KClO3KCl + Oxygen

C H O + O 6 12 6 2

Carbon dioxide +

water

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)

Predict the products

When K reacts with MgF 2 Mg + KF

When Mg reacts with KF NO REACTION

Predict the products

NaOH + KCl

NaNO + KBr3

Ammonium Carbonate +

Magnesium Chloride

Magnesium carbonate as precipitate and ammonium ions and chloride ions as spectators

Terminology….

SPECTATOR ION

Net ionic equation

PRECIPITATE

SINGLE REPLACEMENT

DOUBLE REPLACMENT

COMBUSTION

COEFFICIENT

DECOMPOSITION

SYNTHESIS REACTION

soluble

aqueous

Activity series