Chemical Reactions&

Chemical Equations

Chemical Reactions

A process involving a substance or substances changing into a new substance or substances

Chemical Change

Chemical ReactionsEvidence of a chemical reaction

Chemical ReactionsEvidence of a chemical reaction

1) A permanent color change2) A gas is produced3) Energy is exchanged4) A precipitate is produced

Chemical EquationsA statement using chemical formulas to describe the identities and relative amounts of reactants and products involved in the chemical reaction

Reactant(s) Product(s)

MgCO3 MgO + CO2

MgCO3 CO2 + MgO

MgCO3 (s) MgO (s) + CO2(g)

Phases of Components(s) = solid(l) = liquid(g) = gas(aq) = aqueous

Physical Change Vs.

Chemical Change

Physical Change Chemical Change

Physical Change Chemical ChangePhase ChangesDissolvingMixingBreakingSeparatingFiltering

Rearrange AtomsNew Substances form

Did a chemical change occur?

1. Permanent Color Change Occurs

2. Precipitate Formed

3. Gas is Released

4. Energy is Exchanged – Temperature

Chemical Reaction Demonstration1. Permanent Color Change

CuSO4 (Aq) + Zn (s) ZnSO4 (Aq) + Cu (s)

Blue Gray Clear Black The Zn and Cu are Switching, this is known as a single replacement Reaction.

2. Gas is ProducedHCl (l) + Zn (s) ZnCl (Aq) + H2 (g)

3. Energy is ExchangedMg (s) + O2 (g) MgO (s)

Rapid Oxidation

4. Precipitate is FormedPb(NO3)2 (Aq) + K2CrO4 (Aq) KNO3 (Aq) + PbCrO4 (s)

Clear Bright Yellow

Practice Exercise #11. Define Chemical Reaction2. How do we know a chemical reaction has

taken place?3. What is a Chemical Equation and Why do

we use them?4. What are the initial constituents of a

chemical reaction? What are the end products called?

5. What do the following symbols stand for?s l g aq

Types of Chemical Equations

Synthesis

• Putting things together• Also known as Direct Combination.

2 Na + Cl2 = 2 NaCl

4 Al + 3 O2 = 2 Al2O3

Decomposition

• Breaking things down/Taking apart• AKA Analysis

2 KClO3 = 2 KCl + 3 O2

3 MnO2 = Mn3O4 + O2

Single Replacement

• Replacing one element in a compound with another element.

2 Al + 6 HCl = 2 AlCl3 + 3 H2

2 NaBr + Cl2 = 2 NaCl + Br2

Double Replacement

• Switching one element from a compound with another element from a different compound.

2 AgNO3 + MgCl2 = 2 AgCl + Mg(NO3)2

HCl + NaOH = NaCl + H2O

Others

• Combustion– Rapid Oxidation– XXXX + O2 CO2 + H2O

• Oxidation– Add Oxygen (Combustion)

• Reduction• Acid – Base Neutralization • Etc……

HW

• Due Monday

• Read & outline page 249-255

Exothermic Reactions

• Release or give off heat.• Heat is a byproduct of the reaction.• Temperature increases as the bonds

between products are formed.• Examples

– Combustion, Respiration, Oxidation

Endothermic Reactions

• Take in or absorb Heat from the surroundings.• Temperature decreases as the reaction

progresses.• Heat is used to break bonds of reactants.

– Decomposition or Analysis Reactions

Oxidation

• Removing Electrons

Reduction

• Adding Electrons

Rate of Reaction• Reactions occur at different speeds.• The time it takes for reactants to become

products.

Catalysts

• They speed up reactions without being affected themselves.– They stay the same– Enzymes in living organisms.

• Lowers activation energy– The amount of energy needed to start a reaction.

Speeding Up Reactions

• Temperature, Energy, Pressure, Surface Area, Concentration, Collisions, Catalyst.

Measuring Rates of Reactions

• Measure Reactants• Measure Products

BalancingChemical Equations

Reactant(s) Product(s)

MgCO3 (s) MgO (s) + CO2(g)

Phases of Components(s) = (l) = (g) = (aq) =

1 MgCO3 (s) 1 MgO (s) + 1 CO2(g)

1 MgCO3 (s) 1 MgO (s) + 1 CO2(g)Reactants Products

1 MgCO3 (s) 1 MgO (s) + 1 CO2(g)

5 atoms 5 atoms

H2 + O2 H2O

2 H2 + 1 O2 2 H2O

H2 + H2 + O2 H2O + H2O

2 H2 + 1 O2 2 H2OH2 + H2 + O2 H2O + H2O

Ca + Cl2 CaCl2

Na + Cl2 NaCl

Fe2O3 Fe + O2

AgNO3 + NaCl NaNO3 + AgCl

FeS2 + O2 Fe2O3 + SO2

4 FeS2 + 11 O2 2 Fe2O3 + 8

SO2

NH4OH + Ni(NO3)2 NH4NO3 + Ni(OH)2

 

NH4OH + Ni(NO3)2 NH4NO3 + Ni(OH)2

 

Na2CO3 + Fe(NO3)3 Fe2(CO3)3 + NaNO3

Na2CO3 + Fe(NO3)3 Fe2(CO3)3 + NaNO3

3 Na2CO3 + 2 Fe(NO3)3 Fe2(CO3)3 + 6 NaNO3

Balanced!!!

H3PO4 + Ca(OH)2 Ca3(PO4)2 + H2O

 NH4OH + H3PO4 (NH4)3PO4 + H2O

 

Al(OH)3 + H2SO4 Al2(SO4)3 + H2O

 

C6H6 + O2 CO2 + H2O