chapter 8 reactions in aqueous solution
DESCRIPTION
Chapter 8 Reactions in Aqueous Solution. Will a reaction Occur?. Driving Forces in a Chemical Reaction Formation of a solid Formation of water Formation of a gas Transfer of electrons. Types of Reactions. Double Replacement Reactions 1. Precipitation Reactions - PowerPoint PPT PresentationTRANSCRIPT
Chapter 8
Reactions in Aqueous Solution
Will a reaction Occur?
Driving Forces in a Chemical ReactionFormation of a solidFormation of waterFormation of a gasTransfer of electrons
Types of Reactions Double Replacement Reactions
1. Precipitation Reactions
2. Acid and Base Reactions
Red-ox Reactions 3. Single Replacement Reactions
4. Synthesis Reactions
5. Decomposition Reactions
6. Combustion Reactions
Double Replacement Reactions
1 – Precipitation Reactions
2 – Acid and Base Reactions
Double Replacement Reactions – Reactions involving two compounds in which two elements switch places
General Form:
AB + CD → AD + CB
Double Replacement
Solid Formation: Precipitation Reactions
(#1) Precipitation Reaction – a reaction that produces a precipitate
K2CrO4 (aq) + Ba(NO3)2 (aq) →
BaCrO4 (s) + 2 KNO3 (aq)
In order to know what will form, you need to know what is in solution!
Solid Formation
In solution, most compounds break down into their ions Ba(NO3)2 (aq) → Ba2+
(aq) + 2 NO3
1- (aq)
Strong Electrolyte – completely dissociates into ions in solution (dissolving.mov)
The reaction is best demonstrated by:
2 K1+ (aq) + CrO42-
(aq) + Ba2+(aq) + 2 (NO3)1- (aq) → BaCrO4 (s) + 2 K1+ (aq) + 2 NO3
1- (aq)
Solid Formation - Solubility Rules
Soluble solid – a solid that dissolves in water Insoluble solid – a solid that does not dissolve
in water Slightly soluble solid – a small amount of the
solid dissolves in water
Solid Formation - Solubility Rules
Soluble –NO3
- salts
Na+, K+, NH4+ salts
Cl-, Br-, I- salts, but not when with Ag+, Hg2
2+, and Pb2+
SO42- salts, but not when with Ba2+ , Pb2+,
and Ca2+
Solid Formation - Solubility Rules
InsolubleS2-
CO32-
PO43-
OH-, but not when with Na+, K+, Ca2+
Visualizing Solubility
Describing reactions in Aqueous Solutions
Molecular Equation – Represents all molecules involved in a reaction
Complete Ionic Equation – represents all of the ions in the reacting solution
Net Ionic Equation – shows only the ions directly involved in the reaction, spectator ions are not included
Spectator Ions – ions that are listed in the complete ionic equation, but not in the net ionic equation. They are not involved in the reaction.
Describing reactions in Aqueous Solutions
Molecular Equation Pb(NO3)2 (aq) + Na2SO4 (aq) → PbSO4 (s) + 2NaNO3 (aq)
Net Ionic Equation Pb2+ (aq) + SO4
2-(aq) → PbSO4 (s)
Complete Ionic Equation Pb2+ (aq) + 2(NO3)- (aq) + 2Na1+ (aq) + SO4
2-(aq) → PbSO4 (s) + 2Na+ (aq) + 2NO3
- (aq)
Describing reactions in Aqueous Solutions
Write the balanced molecular, ionic, and net ionic equations: Aqueous sodium chloride is added to aqueous silver
nitrate to form solid silver chloride plus sodium nitrate
Formation of Water: (#2) Acids & Bases
Acid – “acidus” or sour – a substance that produces H+ ions (protons) when it is dissolved in waterStrong acid – completely dissociates in waterHCl(aq) → H1+ (aq) + Cl1- (aq)
Base – “alkalis” slippery in feel and sour in taste – a substance that produces hydroxide (OH) ions in solutionStrong base – completely dissociates in waterNaOH(aq) → Na1+ (aq) + OH1- (aq)
Formation of Water: (#2) Acids & Bases
Formation of Water: Acids & Bases
When acids and bases react, they neutralize each other
Neutralization – When a strong acid and strong base react to form water and an aqueous salt
Acids & Bases
Write the molecular, Complete ionic, and net ionic equation for the reaction of nitric acid and potassium hydroxide
Arrhenius ModelAcids – anything that produces H1+Bases – anything that produces OH1-Strong – Completely dissociates
Bronsted-LowreyAcids – Proton DonorBases – Proton AcceptorWeak – Slightly Soluble, slight dissociation
Acids & Bases
Acid + Base → Conjugate Acid + Conjugate Base
H2SO4 + NaOH → H2O + Na2SO4
To find the conjugate acid – follow the hydrogen
To find the conjugate base - follow the anion from the acid
Acids & Bases
Concentration – How much material is dissolved in your solution Concentrated – much material is dissolved Dilute – little material is dissolved
Molarity – Unit of Concentration in Chemistry The number of MOLES of material per LITER of
solution Unit = M M = moles / L Example: 8M HCl = an 8 Molar solution of
Hydrochloric Acid, 8 moles of HCl are dissolved in every liter of the solution
Acids & Bases
Titration – measuring the exact amount of an acid that reacts with an exact amount of a base. If you know the concentration of one of the solutions,
it can be used to calculate the concentration of the other
Equivalence point – the point of neutralization, the amount of acid and base are equal in solution
Standard Solutions – solutions of known concentration
Acids & Bases
Acids & Bases
Burette – the tool used to dispense an exact amount of a standard solution in a titration
Indicators – substances that change from clear to a color at a specific pH
Acids & Bases
Titration Curve – graphing pH of solution versus volume of base added
M1V1 = M2V2
Used in Acid/Base Used in Dilution
Example Problem: A 100.0mL solution of 0.5M HCl(aq) is titrated with 0.10M
NaOH. What volume of NaOH do you need to reach equivalence?
M 1 V 1 = M 2 V 2
MHClVHCl = MNaOHVNaOH
(100.0mL HCl)(0.50M HCl) = (X mL NaOH)(0.10M NaOH)
X = 500.0mL NaOH
Acids & Bases
pH – measure of acid strength, equal to the molarity of the H+ ions in solution 1-14 scale 1 = strongest acid 14 = strongest base 7 = neutral Logarithmic Scale, a change of 1 pH is different in
concentration by a factor of 10! pOH – measure of base strength, equal to the
molarity of the OH- ions in solution
Acids & Bases
Acids & Bases
Useful pH Equations: pH = -Log[H+] pOH = -Log[OH-] 14 = pH + pOH [H+] = 10(-pH)
[OH-] = 10(-pOH)
[OH-] [H+] = 1 x 10-14
[ ] = symbol of Molarity
Oxidation – Reduction Reactions
3 – Single Replacement Reactions4 – Synthesis5 – Decomposition6 – Combustion Reactions
Oxidation - Reduction
Oxidation/Reduction Reaction – a reaction that involves the transfer of electrons Usually between a metal and nonmetal to form an
ionic compound Involves 2 half reactions
Oxidation – loosing electrons Reduction – gaining electrons Potassium.mov zinc&iodine.mov
Oxidation - Reduction
2 Mg (s)+O2 (g) → 2 MgO (s)
OxidationMg → Mg 2+ + 2e-
ReductionO2 + 4e- → 2O2-
Oxidation - Reduction
Single Replacement Reaction – Single element combines with a compound, replacing one of the members of the compound.
A + BC → AC + B
Oxidation – Reduction: (#3) Single Replacement
Activity / Electromotive Series
Metals Nonmetals lithium fluorine potassium chlorine calcium bromine sodium iodine magnesium aluminum zinc chromium iron nickel tin lead hydrogen copper silver mercury platinum gold
Used to predict if a red-ox reaction will occur
Metals replace metals. Nonmetals replace
nonmetals. The replacing
substance must be more active (higher on the list) than the substance it replaces for a reaction to occur.
Oxidation – Reduction
Predict if a chemical reaction will occur in the following redox reactions:
iron + copper (II) sufate
chlorine + potassium bromide
copper + zinc chloride
Oxidation - Reduction
Oxidation – Reduction: (#4)Synthesis + (#5)Decomposition
Synthesis – Elements combining to make a compound A + B → AB Synthesis.MOV
Decomposition – Compound separating into its constituent elements AB → A + B Decomposition.MOV
Combustion Reactions – any reaction that consumes carbon and oxygen to produce carbon dioxide and water
• General Form: CxHy + O2 → CO2 + H2O
• Example: CH4 + 2O2 → CO2 + 2H2O
Formation of a Gas: Combustion Reactions
Top 4 ReactionsSingle ReplacementDouble DisplacementSynthesisDecomposition
Four Types.movsugar_potassiumchlorate.mov
Other Ways to Classify Reactions
Review – Types of Reactions and Driving Forces
Double Displacement AB + CD → AD + CB Acid Base – Formation of water Multiple - Formation of gas Precipitation - Formation of a solid
Oxidation-Reduction – Driving force for all is transfer of electrons Single Replacement A + BC → AC + B Synthesis A + B → AB Decomposition AB → A + B Combustion CxHy + O2 → CO2 + H2O
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