Chemical Reactions

Chapter 11

How to Make a Cake

1. Add flour and eggs and milk, put in the oven for 20 minutes at 450oF and you will have yourself a cake.

2. Flour(s) + eggs(s) + milk(l) → cake(s)

1. Word Equation: uses names of the

reactants and products.

Ex: aluminum plus copper (II) chloride yields

aluminum chloride and copper

REPLACE THE PLUS WITH A (+) AND THE YIELD WITH AN ()

ALUMINUM + COPPER (II) CHLORIDE ALUMINUM CHLORIDE + COPPER

2. Skeleton Equation: uses chemical

symbols with no relative amounts.

Ex: Al(s) + CuCl2(aq) → AlCl3(aq) + Cu(s)

NOTE!!!!!!!

• Make sure compounds are written properly.

• Remember to put up the charges and use criss-cross method if needed.

• *** Remember the diatomic molecules.

3. Phases:

s - solid phase

l - liquid phase

g - gaseous phase

aq – aqueous phase

(exists in a water solution)

EX: NaCl(aq) = solid NaCl dissolved in H2O

4. Balanced Formula Equation: shows the relative amounts of the atoms on each side of the equation.

EX: 2Al(s) + 3CuCl2(aq)→ 2AlCl3(aq) + 3Cu(s)

LAW OF CONSERVATION OF MATTER

• To balance equations use ONLY coefficients.

• NEVER, NEVER change a subscript

NOTE!!!!!!!

Balancing Reactions

Types of Reactions

1. Combination (Synthesis)

2. Decomposition

3. Single Replacement

4. Double Replacement

5. Combustion

1. Combination (Synthesis):

Ex: A + B → AB

Ex: 2H2 + O2 → 2H2O

2.Decomposition:

Ex: AB → A + B

Ex: 2H2O → 2H2 + O2

(electrolysis)

3.Single Replacement:

Ex: A + BC → C + BA

Ex: Zn + Cu(NO3)2 → ?

Like replaces likeUSE ACTIVITY SERIES

Is Zn higher than Cu on the list?

Activity Series of MetalsUse for single replacement Reactions

LiKBaSrCaNa

Mg AlMn

Zn Zn + Cu(NO3)2 → Zn(NO3)2 + Cu Fe

CdCoNiSnPbHCuAgHgAu

Decreasing A

ctivity

4.Double Replacement:

Ex: AB + CD → AD + CB

Ex: HCl + NaOH → H(OH) + NaCl

5.Combustion:

Ex: hydrocarbon + O2 → CO2 + H2O

Ex: CH4 + 2O2 → CO2 + 2H2O

This is an example of complete combustion.

• These beakers contain 0.1 M solutions of silver nitrate, AgNO3, and iron (III) chloride, FeCl3.

Since we can not see solid particles in these beakers we conclude that silver nitrate and iron (III) chloride are soluble in water.

• Let's check the conductivity of these solutions to be sure these salts form ions when they dissolve in water.

AgNO3 FeCl3

Ionic Equations

To test for ions we will dip the two wires into a solution. If ions are present, the solution will conduct electricity and the bulb will light.

The wires that complete the electrical circuit to

the light bulb have been dipped into a

solution of FeCl3.

Does FeCl3 form ions when it dissolves in

water?YES NO

The wires that complete the electrical circuit to

the light bulb have been dipped into a

solution of FeCl3.

Right, when FeCl3 dissolves in water it forms Fe+3 and Cl-1 ions.

Next let's test silver nitrate.

The wires that complete the electrical circuit to

the light bulb have been dipped into a

solution of AgNO3.

Does AgNO3 form ions when it dissolves in

water?YES NO

The wires that complete the electrical circuit to the light bulb have been dipped into a solution of AgNO3.

Right, when AgNO3 dissolves in water it forms Ag+1 and NO3 -1 ions.

• The conductivity experiments established that silver nitrate and iron (III) chloride form ions in aqueous solution.

• The ions conduct electricity so the bulb lights.

Let's mix the solution of AgNO3 with the solution of FeCl3.

   

 

Mixing yields a white precipitate and a brown solution.

What precipitated?

This is a double replacement rxn

Either AgCl or Fe(NO3)3 formed the ppt

See Table 11.3 on page 344

Fe(NO3)3

-Nitrate salts are soluble

(dissolve and therefore don’t form precipitates)

AgCl-THIS IS THE PPT

We now know the phases:

AgNO3(aq) + FeCl3(aq)→ AgCl(s) + Fe(NO3 )3(aq)

Let's look at the ions formed in the solutions. Not every ion formed is directly involved in the reaction.

We mixed a solution that contained Fe+3 and Cl-1 ions with one that contained Ag+1 and NO3- ions.

AgNO3(aq) + FeCl3(aq)→ AgCl(s) + Fe(NO3 )3(aq)

The Ag+1 and Cl-1 ions reacted to form the ppt, AgCl

Are Fe3+ & NO-3 directly

Involved in the formation

of AgCl?

Net Ionic Equations• Shows what happens to the ions that take

part in chemical reactions.

• Shows dissolved ionic compounds as their free ions.

AgNO3(aq) + FeCl3(aq)→ AgCl(s) + Fe(NO3 )3(aq)

1st BALANCE THE EQUATION:

3AgNO3(aq)+FeCl3(aq)→ 3AgCl(s)+Fe(NO3 )3(aq)

3AgNO3(aq)+FeCl3(aq)→ 3AgCl(s)+Fe(NO3 )3(aq)

2nd WRITE THE IONIC EQUATION:

Only for aqueous solutions3Ag+ +3NO3

- + Fe+3 +3Cl-→3AgCl(s)+Fe+3+3NO3-

3rd CANCEL OUT THE SPECTATOR IONS:

• Ions that undergo no chemical change & aren’t directly involved during a chemical reaction.

• Appear on both sides of the chemical reaction.

3Ag+ +3NO3- + Fe+3 +3Cl-→3AgCl(s)+Fe+3+3NO3

-

Cancel out all spectator ions

4th WRITE THE NET IONIC EQUATION:

Rewrite equation leaving out spectator ions.3Ag+ +3NO3

- + Fe+3 +3Cl-→3AgCl(s)+Fe+3+3NO3-

3Ag+(aq) + 3Cl-(aq)

→ 3AgCl(s)

Reduce coefficients

Ag+(aq) + Cl-(aq)

→ AgCl(s)

So, Fe+3 & NO3-1 weren’t directly involved in

the formation of AgCl.

EX: Cl2(g) + NaBr(aq) → Br2(l) + NaCl(aq)

1st: write ionic eq

Cl2(g) + Na+ + Br - → Br2(l) + Na+ + Cl –

2nd: cancel out spectator ions

Cl2(g) + Na+ + Br - → Br2(l) + Na+ + Cl –

3rd: write net ionic eq

Cl2(g) + Br - → Br2(l) + Cl –

4th: balance final net ionic eq

Cl2(g) + 2Br - → Br2(l) + 2Cl –

Practice on Your Own

Do question #32 a

On page 344