Chemical EquationsThat’s what it’s ALL about

Grooooovey baby…yeah!!

What is a chemical equation? It is a symbolic representation of a chemical

reaction, that is balanced and represents the states of matter

That’s soooo exciting!…yeah ok, not really

And I want to know this because…… It is good to know whether a reaction will

take your face off BEFORE you actually throw the chemicals together

Still not sure I get the concept

Think of chemical equation in the

same way that you might think of

a recipe for chocolate chip cookies.

You have ingredients, then you

prepare them, then you get cookies

Can I get my cookies with some Frikin’

Chocolate “chunks?”

Yummy!!!

Ingredients -----------> Bake ----------->Cookies

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

2 1/2 (1 ounce) squares unsweetened chocolate

1/2 cup butter

2 cups all-purpose flour

1/2 teaspoon baking soda

1 teaspoon baking powder

1/4 teaspoon salt

1 1/4 cups white sugar

2 eggs

1 teaspoon vanilla extract

2/3 cup sour cream

2 cups semisweet chocolate chips

--------------------->

It isn’t different in Chemistry… You just don’t eat the cookiesIngredients -----------> Bake -----------> Cookies

Chemistry:

Reactants ------------------------------> Products

Example: O2 + H2 ----------------> H2O (+ enough energy to melt your face)

What happened to the other Oxygen????

yields

Law of conservation of matter

Matter can not be created nor destroyed by ordinary chemical processes

So we have to balance the previous equation

Using coefficients OONNLLYY!!!!!!!!!!!!O2 + H2 ----------------> H2O

ONCE AGAIN….

COEFFICIENTS

ONLY!!!!!!!!!

Here is how this equation looks balanced:

O2 + 2H2 ----------------> 2H2O

How do I balance an equation?The basic concept is to use coefficients ONLY to

be sure that there are the same number of moles of stuff on the left side as there are on the right.

This can be done by counting single elements on both sides and look for lowest common factors

This could get a bit tedious…are there some shortcuts?

Yes: Look for polyatomic ions common on both sides

and treat them as one element Look for lowest common factors to determine

the correct coefficients ALWAYS double check when you are done!!!!

Anything else I need to know about equations??

Oh YEEEES! States of matter of each reactant and

product Reaction types and other CRAPO(N) Metal activity Nonmetal activity Solubility Endo/Exothermic

STATES OF MATTER OF REACTANTS AND PRODUCTS

Since some chemicals react differently (or are more dangerous) when they are liquids, solids, or gasses, it is useful to determine this ahead of time Greenhouse solids would

be a lot better than greenhouse gasses

HERE ARE THE MOST COMMON WAYS TO EXPRESS STATES OF

MATTER

SOLID (s) LIQUID (l) GAS (g) AQUEOUS (DISSOLVED IN WATER) (aq) CRYSTALLINE (cr)There are one or two other obscure ones but these are the

real important ones

Here is how they are used

O2(g) + 2H2(g) ----------------> 2H2O(l)

That is sooo clever!!!

THIS IS A BUNCH OF….

CRAP!!!!

ACTUALLY…IT’S:C R A P O (N)O E C R R UM D I E G CP O D C A LL X B I N EE A P I AX S I C R

I E TO AN T

E

THAT’S RIGHT….ALL CHEMICAL REACTIONS CAN ACTUALLY BE CLASSIFIED AS

CRAPO

(NUCLEAR IS NOT CLASSIFIED AS CHEMICAL)

UNFORTUNATELY, THIS IS NOT THE TRADITIONAL WAY TO CLASSIFY EQUATION TYPES….

I KNEW IT!!

EQUATION (REACTION) TYPES SYNTHESIS

To Put Together or Produce

A + B -------> AB

Example:

H2 + O2 -----------> H2O

Can you see that this is a “putting together” process?

DECOMPOSITION

TO BREAK DOWN

AB -----------> A + B

EXAMPLE:

H2O2 -----------> H2O + O2

CAN YOU SEE THAT THIS IS BREAKING DOWN?

SINGLE DISPLACEMENT (REPLACEMENT)

TO REPLACE A SINGLE ION WITH ANOTHER

AB + C ------------> AC + B (OR CB + A)

EXAMPLE:

HCl + Mg ----------> MgCl2 + H2

Can you see that C has replaced A in the equation?

DOUBLE DISPLACEMENT (REPLACEMENT)TO SWAP TWO CATIONS OR TWO

ANIONS AB + CD ----------> AD + CB

EXAMPLE:

NaOH + H2SO4 -------> HOH + Na2SO4

Can you see that the two cations have switched places?

(ORGANIC) COMBUSTIONTO COMBUST A CARBON-BASED COMPOUND

(USUALLY HYDROCARBON) WITH O2 TO FORM CO2 AND H2O

CXHX + O2 ---------> H2O + CO2

EXAMPLE:

C2H6 + O2 ---------> H2O + CO2

CAN YOU SEE THE HYDROCARBON REACTING WITH OXYGEN AND MAKING CARBON DIOXIDE AND WATER?

From now on… We will refer to CRAPO(N) as Classes of

reactions

And Synthesis, Decomposition, Single displacement, Double displacement, and combustion as equation types

ACTIVITY SERIES!!!!!

Do reactions occur every time chemicals are put together?

Of course not…if they did we would change every time we came in contact with another chemical

Help me!!I’m melting

When a single element is reacting with a compound

The reaction can only occur if the single element is more active than the anion or cation in the compound that it is replacing

Bottom line: the most active elements will be in the bond.

Example

NaOH + Pb -----------> ?

Na is more active than Pb

Will Pb replace Na?

NO!!!!!!!!

Remember the most active elements will be in the bond

Example

K + Cu(OH)2 ----------->?

K is more active than Cu

Will THIS reaction occur?

You Bet!!!!

K + Cu(OH)2 -----------> KOH + Cu

Now we balance it and add the states of matter:

VOILA!!!

2K(s)+ Cu(OH)2(aq) ---------> 2KOH(aq) + Cu(s)

Do I need to memorize the activity series?

NO: Cation activities (mostly metals) are determined experimentally, so you will have a chart, and anion activity series is mostly determined by electronegativity, and this is mainly with the Halides (Halogens) only.

Activity series for metals

LiKBaSrCaNaMgAlMnZnFeCdCoNiSnPbHCuAgHgAu

The metals on top Are more active Than the onesBelow it

Activity series for nonmetals

Simple: Since halides are involved in most replacement type reactions, just remember that the halide higher up on the periodic table will replace the one below it, or in other words the higher, the more active

SOLUBILITY

Have you noticed, in some reactions, that solids form when you mix 2 aqueous chemicals? How is this possible?

Easy: Sometimes chemicals form in a reaction that don’t dissolve in water…they are insoluble-solid

Solubility Definitions

Soluble: Will or is dissolved in a solvent (usually water)

Insoluble: Will not or isn’t dissolve in a solvent

Precipitate: A solid formed from the mixing of two aqueous liquids

More Definitions

Solute: A substance which is dissolved in a solvent

Solvent: A substance which dissolves another substance

Saturation: The formation of more soluble product than a solution can hold at a particular temperature and pressure

How do I know what makes a precipitate?

Compounds containing the following are generally soluble in water

1) Alkali metal ions, and ammonium ions2) Acetate ions3) Nitrate ions4) Halide ions except with: Ag+, Hg2+, and Pb2+

5) Sulfate ions, except with: Sr2+, Ba2+, Pb2+

More Solubility RulesCOMPOUNDS WITH THE FOLLOWING ARE GENERALLY INSOLUBLE IN WATER

6) Carbonate ions (Unless any are paired with those in rule one, which makes these soluble)

7) CrO42- Chromate ions (Unless any are paired with those in rule one,

which makes these soluble)8) Phosphate ions (Unless any are paired with those in rule one,

which makes these soluble)9) sulfide ion (Unless any are paired with those in rule one, which

makes these soluble, as does CaS, SrS, BaS)10) Hydroxide ions (Unless any are paired with those in rule one,

which makes these soluble, as does Ca(OH)2, Sr(OH)2, and Ba(OH)2 here)

PRACTICE-Write the products and predict the precipitate

AgNO3 + NaOH ----->

NH4OH + Na2CrO4------->

ANSWERS

AgNO3 + NaOH -----> AgOH + NaNO3

NH4OH + Na2CrO4-----> (NH4)2CrO4 + NaOH

Blue indicates the insoluble precipitate

CONGRATULATIONS

YOU ARE NOW EXPERTS IN CHEMICAL EQUATIONS!!!

You can use this information for Evil…

Release the “CO2” to start the “global Warming”

Or For Good…. Green is Groovey Baby…Yeah!!!!