Types of Reactions

5 Types of Chemical Reactions

Synthesis (Combination) reaction

Decomposition reaction

ASingle-replacement reaction

BDouble-replacement reaction

Combustion reaction (of a hydrocarbon)

A + B AB

AB A + B

A + BC AC + B

AB + CD AD + CB

CxHy + O2 CO2 + H2O + energy

Ause activity series to predictB use solubility chart to predict

Synthesis Reactions

General Formula: A + B AB

A is an elementB is an elementAB is a compound

Always write the correct formula for the compound based on the charges of the ions BEFORE balancing!

(identifying characteristic: only ONE product!)

Hints!! Don’t forget the formulas for diatomic elements, aka the “7-ups”

Synthesis ReactionExample: Sodium + chlorine

Na(s) + Cl2(g)

Na1+ Cl1-

1. Write the formulas for the reactant elements, including states of matter

2. Write the correct formula for the product compound based on the charge of the ions (remember that ionic compounds are solid at room temperature unless they are dissolved in water).

NaCl

Na(s) + Cl2(g) NaCl (s)

3. Balance the equation

22

Synthesis Reaction

Direct combination reaction (Synthesis)

General form: A + B AB

element element compound

Na+Cl -

Na

ClNa

Cl

Na+ Cl -

2 Na + Cl2 2 NaCl

Try this one!

Potassium + oxygen

The answer is…..

4 K(s) + O2 (g) 2 K2O (s)

K1+ O2-

K O

1 2

K2O

Write the ions

CrissCross the charges

Reduce if needed, ignore “1”

Decomposition Reactions

General formula: AB A + BIdentifying characteristic: only ONE reactant!

AB is a compoundA is an elementB is an element

Decomposition Reaction

Ex: decomposition of water

1. Write the formula of the reactant compound

H2O(l)

2. Write the formulas of the element products

H2(g) + O2(g)

3. Balance the equation

2 2

Decomposition Reaction

O O

O

HH

HH

H

H

H

HO

Decomposition reaction

2 H2O(l) 2 H2 (g) O2 (g)

General form: AB A B

+

+

+compound two or more elements

or compounds

Try this one!

The decomposition of iron(III) oxide(HINT: the roman numeral tells you the charge of the iron!)

2 Fe2O3(s) 4 Fe(s) + 3 O2(g)

Combustion Reactions

CxHy + O2 CO2 + H2O + energyA hydrocarbon*

•A hydrocarbon is a molecule that consists of carbonand hydrogen

Identifying characteristic:hydrocarbon and oxygen

Tips on Balancing Combustion Reactions

1. Do an Atom Inventory

2. 1st, balance the carbons

3. 2nd, balance the hydrogens

4. 3rd, balance the oxygens

5. If the oxygens don’t balance with a whole number, balance with a ½ number, THEN multiply all coefficients by 2.

Combustion of a Hydrocarbon

Many homes get heat from propane (C3H8) heaters. Write a balanced chemical equation for the completecombustion of propane gas.

C3H8(g) + O2(g) CO2(g) + H2O(g) + energy

C

H

O

3 18 2

2 3

1st Balance Carbons

3

/

/

3

7

2nd Balance hydrogens

/

4

8

3rd Balance oxygens

/ 10

5

/10

Do an Atom Inventory

Combustion of Methane Gas

Davis, Metcalfe, Williams, Castka, Modern Chemistry, 1999, page 245

One methane molecule

Two oxygen molecules

One carbondioxide molecule

Two water molecules

CH4 2 O2CO2 2H2O

1 carbon+

4 hydrogen4 oxygen

1 carbon+

2 oxygen

2 oxygen

+ 4 hydrogen

+ ++ energy

+

Heat and flame

Try this one!

Write the complete combustion equation for butane gas(formula for butane is C4H10). Butane is the gas found in lighters.

The answer is…….

2 C4H10 + 13 O2 8 CO2 + 10 H2O + energy

3. Balance O: C4H10 + O2 4 CO2 + 5 H2O + energy

1. Balance C: C4H10 + O2 CO2 + H2O + energy

2. Balance H: C4H10 + O2 4 CO2 + H2O + energy

4

5

(hint: need to use a ½)

6.5

4. Double all coefficients:

C4H10 + O2 CO2 + H2O + energy132 8 10

Single Replacement Reactions

General Formula: A + BC B + AC

Need to use an Activity Series to determine if a reaction will occur

Identifying characteristic: reactantsare an ELEMENT and a COMPOUND

A is an elementBC is a compoundA and B switch places to form: B (an element) and AC (a compound)

Single Replacement Reactions

Single-replacement reaction

Mg + CuSO4 MgSO4 + Cu

General form: A + BC AC + B

How do you know if Mg switches places with the Cu or the SO4?

If the element A forms a cation, it replaces the cation in the compound BC

If the element A forms an anion, it replaces the anion in the compound BC

Help, I need a review!!

What is a cation and an anion?

A cation is a “+” charged ion An anion is a “-” charged ion

Ionic Compounds are ALWAYSwritten cation then anion!!

Ex: MgCl2 Mg2+ Cl1-

Activity Series: Will a reaction occur ?

Element ReactivityLiRbKBaCaNaMgAlMnZnCrFeNiSnPbH2

CuHgAgPtAu

Halogen Reactivity

F2

Cl2Br2

I2

Al

Cu

Foiled again!Aluminum beats Copper!

Al (the element) is higher on the chart than Cu (in the compound)

Al is STRONGER so overtakes/replaces Cu in the compound andKicks Cu out by itself! Al

Cu

Al(s) + CuSO4 (aq)The cation list

The anion list

Aluminum vs copper II sulfate

Al (s) + CuSO4 (aq)

Al is higher on the chart than Cu, so it kicks Cu out of the compound.

Cu

Al then makes a compound with SO4

Al3+ SO42-3 2

Al (SO4)

+ Al2(SO4)3(aq)(s)

Now, balance the equation.

2 3 3

Your turn!

Will a reaction occur? Yes or No If “Yes”, write a complete balanced equation

NaNO3(aq) + Ag(s) ??

F2(g) + NaI(aq) ??

LiRbKBaCaNaMgAlMnZnCrFeNiSnPbH2

CuHgAgPtAu

F2

Cl2Br2

I2

Element Reactivity

Halogens

The Answers…

NaNO3(aq) + Ag(s) NR (abbrev for no reaction)

F2(g) + 2 NaI(aq) 2 NaF(aq) + I2(g)

Why? Because Ag (the element) is NOT higher on the chart than Na

Why? Because F2 IS higher on the chart than I2

Since F2 becomes the F- anion, it replaces the anion in NaI

Potassium reacts with Water

P O W !

*

2 HOH

* Often times it helps to think of water as HOH

Double Replacement Reactions

AB + CD CB + AD

Watch how the cations switch places!

A reaction ONLY occurs if at least ONE of the products is a solid (or H2O).A solubility chart is needed to determine if the products are solids or remain dissolved (aqueous).

Identifying characteristic:Both reactants are ionic compounds

1. Will Al(NO3)3

dissolve in water2. Will barium

phosphatedissolve in water?

3. Will PbI2 dissolve in water?

1. Yes2. No 3. No

Double Replacement ReactionsWill a reaction occur?

K2CO3(aq) + BaCl2(aq)

1. Determine the two products based on the charge of the ions

BaCO3 + KCl

2. Using the solubility chart, determine if each product is a. Aqueous (which means it is soluble in water)b. Solid (which means it is insoluble in water)

(s) (aq)

3. If one of the products is a solid, the reaction occurs, so BALANCE it

2

4. If BOTH products are aqueous, then NO REACTION occurs.Cross out products and write “NR”

Double Replacement Reaction

Double Replacement Practice

NaNO3(aq) + KCl (aq)

H2CO3(aq) + NH4(OH)(aq)

AgNO3(aq) + KCl(aq)

NaCl (aq) + KNO 3(aq)

(NH4)2CO3(aq) + 2 HOH(l)

NR

Formation of a solid AgCl

AgNO3(aq) + KCl(aq) KNO3 (aq) + AgCl(s)