Thanksgiving Gifts from Photosynthesis ORNature’s Chemistry at It’s Best

Thanksgiving Gifts from Photosynthesis

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Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

1. identify various types of chemical reactions

2. identify the processes and driving forces behind different types of reactions

3. Write equations for different types of reactions

Learning Goals – I will be able to…

Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

Formation of a SolidPrecipitation, a Double Displacement Reaction

(covered in 8.1)

• General equation: AB + CD AD + CB

• Precipitation reaction

• Double displacement/replacement reaction

Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

Formation of Water: Acids and Bases (not in notes):A different type of double replacement reaction

A strong acid is one in which virtually every molecule dissociates (ionizes) in water to an H+ ion and an anion.

Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

A strong base is a metal hydroxide that is completely soluble in water, giving separate OH ions and cations.

Formation of Water: Acids and Bases (not in notes)

– Most common NaOH, KOH

Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

Formation of Water: Acid-Base Reaction, a Double Replacement Reaction

(not in notes) • The products of the reaction of a strong acid and a

strong base are water and a salt. • Net ionic equation

H+(aq) + OH−(aq) H2O(l)

• Reaction of H+ and OH− is calledan acid-base reaction.

H+ acidic ion

OH− basic ion• The other anion/cation pair forms a

Salt (Ionic compound)

* NOTICE THAT IF THE PROPER

AMOUNTS OF ACID AND BASE ARE

MIXED THE PH OF THE SOLUTION WILL BECOME

NEUTRAL. *

Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

• Acids and bases are both ionic compounds strong acids/bases are strong electrolytes.

• Acids produce H+ ions in water.• Bases produce OH- ions in water.• Water is a very stable compound strong

tendency for reaction to happen.

Acid + Base Water + Salt

HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq)

Net Ionic Equation: H+(aq) + OH−(aq) H2O(l)

Formation of Water: Acid-Base Reaction, a Double Replacement Reaction

(notes summary)

Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

Transfer of Electrons -- Reactions of Metals with Nonmetals (Oxidation-Reduction)

Reactions between metals and nonmetals involve a transfer of electrons from the metal to the nonmetal.

Oxidation–reduction reaction (redox)

Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

Transfer of Electrons:Oxidation-Reduction Reactions

• A metal and a nonmetal combine to form an ionic compound. Ex.:

2Na(s) + Cl2(g) 2NaCl(s)

• Electron transfer:– sodium is “oxidized” loses one electron– chlorine is “reduced” gains one electron

Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

Single Replacement – One Ion Replaced

• Driving force:

– Transfer of electrons

General equation: A + BC B + AC

Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

Single Replacement Reaction – One Ion Replaced (another example)• Driving forces:

– Transfer of electrons– Formation of a Gas

Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

Involve oxygen & produce a flame (energy released rapidly)

CH4(g) + 2O2(g) CO2(g) + 2H2O(g)

• Combustion Reactions

Types of Oxidation-Reduction Reactions (Redox)

A compound forms from simpler materials

C(s) + O2(g) CO2(g)

• Synthesis (Combination) Reactions

A compound is broken down into simpler substances

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

• Decomposition Reactions

• Single Replacement (seen before) – new ion forms

Section 8.2

Other Reactions in Aqueous Solutions

Sections 8.2-8.3

Ways to Classify Reactions (notes summary)

• Precipitation – a solid forms• Double Replacement (Displacement) – two ions

exchanged/replacedEx.: acid-base, precipitation

• Single Replacement – one ion replaced• Combustion – energy is released, flame; oxygen is

a reactant• Synthesis – reactants combine to form product(s)• Decomposition – reactant breaks down into

products

* Refer to reaction sheet to see examples. *

*REDOX REACTIONS*