Chemical Reactions

Types of Reactions

Synthesis reactions Decomposition reactions Single displacement

reactions Double displacement

reactions

CO……. Types of Reactions

Combustion reactions decomposition reactions precipitation reactions neutralization reactionso acido base

oxidation-reduction reaction

You need to be able to identify each type.

1. Synthesis

Example C + O2

OO C + O O C

H2 +1/2O2 H2O

General: A + B AB

Ex. Synthesis Reaction

EXPLOSIVE ??

????

Practice• Predict the

products.

Na(s) + Cl2(g)

Mg(s) + F2(g)

Al(s) + F2(g)

NaCl(s)

MgF2(s)

AlF3(s)

• Now, balance them. ?

SOLUTION

Na(s) + Cl2(g)

Mg(s) + F2(g)

Al(s) + F2(g)

NaCl(s)

MgF2(s)

AlF3(s)

22

2 3 2

2. Decomposition

Example: NaCl

General: AB A + B

Cl Na Cl + Na1/2 2

Ex. Decomposition Reaction

3. Single DisplacementExample: Zn + CuCl2

ZnClCl Cu +

General: AB + C AC + B

ClCl Zn Cu+

Zn was oxidized

Went from neutral (0) to (+II )

Cu was reduced

Went from (+II) to Neutral (0)

Ex. Single Replacement Reaction

Single Replacement Reactions

• Write and balance the following single replacement reaction equation:

• Zn(s) + HCl(aq) ZnCl2 + H2(g)

2

• NaCl(s) + F2(g) NaF(s) + Cl2(g)

• Al(s)+ Cu(NO3)2(aq)

2 2

Cu(s)+ Al(NO3)3(aq)3 232

4. Double displacement

Example: MgO + CaS

General: AB + CD AD + CB

SOMg Ca

+O S

Mg Ca+

Double Replacement Reactions

• Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together

• Example: AgNO3(aq) + NaCl(s) AgCl(s) + NaNO3(aq)

• Another example:K2SO4(aq) + Ba(NO3)2(aq) KNO3(aq) + BaSO4(s)

2

Practice

• Predict the products. 1. HCl(aq) + AgNO3(aq)

2. CaCl2(aq) + Na3PO4(aq)

3. Pb(NO3)2(aq) + BaCl2(aq)

4. FeCl3(aq) + NaOH(aq)

5. H2SO4(aq) + NaOH(aq)

6. KOH(aq) + CuSO4(aq)

5. Combustion Reactionsa. Combustion reactions

hydrocarbon reacts with oxygen gas.

• This is also called burning!!!

In order to burn something you need the 3 things in the “fire triangle”:

1)Fuel (hydrocarbon)2) Oxygen 3) Something to ignite the

reaction (spark)

Combustion ReactionsIn general:

CxHy + O2 CO2 + H2O + heat

Products are ALWAYS carbon dioxide and water.

(although incomplete burning does cause some by-products like carbon monoxide)

Combustion is used to heat homes and run automobiles (octane, as in gasoline, is C8H18)

CombustionExample

C5H12 + O2 CO2 + H2O

H.W:.

Write the products and balance the following combustion reaction: C10H22 + O2 ?????

5 68

Precipitation Reactions

The process of separating a substance from a solution as a solid.

AgNO3 + NaCl ---> AgCl + NaNO3

precipitate

Neutralization Reactions

• acid• base• salt

Household acids and Bases

Neutralization Reactions

• AcidAny of a large class of sour-tasting

substances whose aqueous solutions are capable of turning blue litmus indicators red, of reacting with and dissolving certain metals to form salts, and of reacting with bases or alkalis to form salts.

Substance that donates H+ ions to solution

Neutralization Reactions

• Base

Any of a large class of compounds, including the hydroxides and oxides of metals, having a bitter taste, a slippery solution, the ability to turn litmus blue, and the ability to react with acids to form salts.

Substance that donates a OH-1 ion to solution

Neutralization Reactions

• salt The term salt is also applied to substances

produced by the reaction of an acid with a base, known as a neutralization reaction.

Salts are characterized by ionic bonds, relatively high melting points, electrical conductivity when melted or when in solution, and a crystalline structure when in the solid state.

Neutralization Reactions

acid + base ---> “salt” + water

Neutralization Reactions

acid + base ---> “salt” + water

HCl + NaOH ---> NaCl + H2O

Neutralization Reactions

acid + base ---> “salt” + water

H2SO4 + 2KOH ---> K2SO4 + 2H2O

Strong vs. Weak Acids and Bases

strong - completely ionizedweak - partially ionized

Oxidation-Reduction Reaction

Oxidation - loss of electrons Reduction - gain of electronsRedox reactionoxidizing agent - substance that causes

oxidationreducing agent - substance that cause

reduction

Decomposition Reactions

Separation into constituents by chemical reaction.

Homogenous EquilibriumHomogenous Equilibrium

Consider colorless frozen N2O4. At room temperature, it decomposes to brown NO2:

N2O4(g) 2NO2(g).

At some time, the color stops changing and we have a mixture of N2O4 and NO2.

Chemical equilibrium is the point at which the concentrations of all species are constant.

The Equilibrium ConstantThe Equilibrium Constant

For a general reaction in the gas phaseaA + bB ═ cC+ dD

the equilibrium constant expression is

Keq = pcC pdD

paA pbB

where Keq is the equilibrium constant.

The Equilibrium ConstantThe Equilibrium Constant

For a general reaction aA +Bb ═ cC + dD

the equilibrium constant expression for everything in solution is

Keq= [C]c[D]d

[A]a[B]b

where Keq is the equilibrium constant.

Homogenous EquilibriumHomogenous EquilibriumAt equilibrium, as much N2O4 reacts to

form NO2 as NO2 reacts to re-form N2O4:

The double arrow implies the process is dynamic.

ConsiderForward reaction: A B Rate = kf [A]

Reverse reaction: B A Rate = kr [B]

At equilibrium kf [A] = kr [B].

The End