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5 Oct. 2010. Objective: SWBAT describe properties of an aqueous solution, and write an equation for a precipitation reaction. Do now: What is an electrolyte? Describe why it exhibits the properties of an electrolyte. Agenda. Do now Aqueous solutions notes

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5 oct 2010
5 Oct. 2010
  • Objective: SWBAT describe properties of an aqueous solution, and write an equation for a precipitation reaction.
  • Do now: What is an electrolyte? Describe why it exhibits the properties of an electrolyte.
agenda
Agenda
  • Do now
  • Aqueous solutions notes
  • Precipitation Reaction practice problems

Homework: p. 160 #1-6, 8-14 evens (JR)

p. 161 #15, 18-24 evens (TTL)

introduction
Introduction
  • Most chemical reactions and virtually all biological processes take place in water!
  • Three categories of reactions in aqueous solutions:
    • Precipitation reactions
    • Acid-Base reactions
    • Redox reactions
slide5

solvent: the part of a solution doing the dissolving, present in larger amount

  • solute: a substance being dissolved, present in a smaller amount
  • solution: homogeneous mixture of two or more substances

SOLUTE

SOLUTION

SOLUTION

SOLVENT

examples
Examples
  • KCl in water?
  • Carbon dioxide in water?
  • Alcohol in water?
  • Now: only solutions in which the solvent is water, and the solute is a liquid or a solid.
properties of an aqueous solution
Properties of an Aqueous Solution
  • Are either electrolytes or nonelectrolytes
  • Electrolyte: a substance that, when dissolved in water, results in a solution that can conduct electricity.
      • ex: NaCl dissolved in water: solid NaCl dissociates into Na+ and Cl- ions
  • Nonelectrolyte: does not conduct electricity when dissolved in water.
      • ex: pure water
strong vs weak electrolytes
Strong vs. Weak Electrolytes
  • Strong: Solute is 100% dissociated in water
    • http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf
    • Why is water good at hydrating ions?
slide9

Acids and bases are electrolytes:

  • Some are strong:
  • Some are weak and ionize incompletely:
  • Double arrow indicates a reversible reaction: reaction can occur in both directions
reversible reaction
Reversible Reaction
  • Molecules ionize and then recombine
  • Until ionization is occurring as fast as recombination: chemical equilibrium
precipitation reactions
Precipitation Reactions
  • formation of an insoluble product (precipitate) which separates from the solution.
  • This is also an example of a double displacement reaction
solubility
Solubility
  • How do you predict whether a precipitate will form?
  • Depends on the solubility of the solute
    • p. 125-126
  • Examples:
    • FeCO3
    • KCl
    • AgCl
practice determining solubility
Practice Determining Solubility
  • Ag2SO4
  • CaCO3
  • Na3PO4
  • CuS
  • Ca(OH)2
  • Zn(NO3)2
writing equations
Writing Equations
  • We don’t always write the entire chemical equation as if each species existed as a complete molecule
    • This doesn’t really reflect what’s actually happening!
molecular equations
Molecular Equations
  • Written as though all species existed as molecules or whole units.
  • Doesn’t always reflect reality.
  • What’s actually happening?
    • Dissolved ionic compounds dissociate into ions!!
ionic equation
Ionic Equation
  • Shows dissolved species as free ions.
  • Notice that there are ions that show up on both sides of the equation.
    • Spectator ions
    • They can be eliminated.
net ionic equation
Net Ionic Equation
  • To give this net ionic equation showing species that actually take place in the reaction:
example 1
Example 1
  • Solutions of barium chloride and sodium sulfate react to produce a white solid of barium sulfate and a solution of sodium chloride.
example 2
Example 2
  • A potassium phosphate solution is mixed with a calcium nitrate solution. Write a net ionic equation.
example 3
Example 3
  • Solutions of aluminum nitrate and sodium hydroxide are mixed. Write the net ionic equation for the reaction.
7 oct 2010
7 Oct. 2010
  • Objective: SWBAT define and describe acids and bases as Arrhenius or Bronsted, and as strong or weak.
  • Do now: Soluble or insoluble? (try first without using your chart!)
    • Ca3(PO4)2
    • Mn(OH)2
    • AgClO3
    • K2S
agenda1
Agenda
  • Homework check (ELS)
  • Acids and Bases: Definitions, strong and weak
  • Neutralization Reactions

Homework: p. 161 #26, 27, 28, 29, 30, 32, 34 (JMS)

Read p. 135-145 and do practice exercises

a-d on p. 145

properties of acids and bases
Properties of Acids and Bases
  • Arrhenius definition:
    • Acids: ionize in water to produce H+ ions
    • Bases: ionize in water to produce OH- ions
acids
Acids
  • React with metals like Zn, Mg, Fe to produce hydrogen gas

2HCl(aq) + Mg(s)  MgCl2(aq) + H2(g)

  • React with carbonates and bicarbonates to produce CO2(g)

2HCl(aq) + CaCO3(s) CaCl2(aq) + H2O(l) + CO2(g)

HCl(aq) + NaHCO3(s)  NaCl(aq) + H2O(l) + CO2(g)

slide27

Brønsted Definition

    • Acid: proton donor
    • Base: proton acceptor
    • don’t need to be aqueous!
  • HCl(aq)  H+(aq) + Cl-(aq)

proton

slide28
But…
  • HCl(aq)  H+(aq) + Cl-(aq)
  • H+ is very attracted to the negative pole (O atom) in H2O
  • HCl(aq) + H2O(l)  H3O+(aq) + Cl-(aq)
  • H3O+ : hydronium ion
  • Above, a Brønstedacid (HCl) donates a proton to a Brønstedbase (H2O)
types of acids
Types of Acids
  • Monoprotic: each one yields one hydrogen ion upon ionization
    • Ex: HCl, HNO3, CH3COOH,
  • Diprotic: each gives two H+ ions
    • Ex: H2SO4
    • H2SO4(aq)  H+(aq) + HSO4-(aq)
    • HSO4-(aq) > H+(aq) + SO42-(aq)
  • Triprotic: 3 H+
strong vs weak acids
Strong vs. Weak Acids

Strong Acids

Dissociate completely

Weak Acids

Dissociate Incompletely

  • HCl hydrochloric
  • HBrhydrobromic
  • HI hyroiodic
  • HNO3 nitric
  • H2SO4 sulfuric
  • HClO4perchloric
  • HF hydrofluoric
  • HNO2 nitrous
  • H3PO4 phosphoric
  • CH3COOH acetic
br nsted bases
Brønsted Bases
  • H+(aq) + OH-(aq)  H2O(l)
    • Here, the hydroxide ion accepts a proton to form water.
    • OH- is a Brønstedbase.
  • NH3(aq) + H2O(l)  NH4+(aq) + OH-(aq)
br nsted acid or base
Brønsted Acid or Base?
  • HBr
  • NO2-
  • HCO3-
  • SO42-
  • HI
acid base neutralization
Acid-Base Neutralization
  • reaction between an acid and a base
    • produce water and a salt
    • salt: ionic compound (not including H+ or OH- or O2-)
    • acid + base  water + salt
  • Strong acid + Strong base example
    • HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)
    • Write the ionic and net ionic equations!
    • Which are spectator ions?
slide34

Weak acid + Strong base example:

    • HCN(aq) + NaOH(aq)  NaCN(aq) + H2O(l)
      • HCN does not ionize completely
    • HCN(aq) + Na+(aq) + OH-(aq) 

Na+(aq) + CN-(aq) + H2O(l)

    • Write the net ionic equation
acid base reaction gas formation
Acid-Base Reaction: Gas Formation
  • Some salts (with CO32-, SO32-, S2-, HCO3-) react with acids to form gaseous products

Na2CO3(aq) + 2HCl(aq)  2NaCl(aq) + H2CO3(aq)

Then the carbonic acid breaks down:

H2CO3(aq)  H2O(l) + CO2(g)

homework
Homework
  • p. 161 #26, 27, 28, 29, 30, 32, 34 (JMS)
  • Bring your book to class!
13 october 2010
13 October 2010
  • Objective: SWBAT model the transfer of electrons between reactants in redox reactions by correctly writing oxidation and reduction half reactions and overall reactions; determine oxidation numbers.
  • Do now: Write balanced molecular, ionic and net ionic equations for this reaction between a weak acid and a strong base:

H3PO4(aq) + Ba(OH)2(aq)

agenda2
Agenda
  • Do now
  • Read objective, debrief do now, review agenda
  • Homework presentation
  • Notes: Writing redox half reactions and assigning oxidation numbers
  • Practice problems
  • Discussion of types of redox reactions (p. 139-145)

Homework: p. 162 #37, 40, 43, 44, 45, 47, 50, 54, 55 (PD), read p. 139-145

14 october 2010
14 October 2010
  • Objective: SWBAT model the transfer of electrons between reactants in redox reactions by correctly writing oxidation and reduction half reactions and overall reactions; determine oxidation numbers.
  • Do now: Write and label (ox. or red.) the two half-reactions:

Cu(s) + 2AgNO3(aq)  Cu(NO3)2 (aq) + 2Ag(s)

agenda3
Agenda
  • Do now
  • Read objective, debrief do now, review agenda
  • Homework presentation
  • Notes: Writing redox half reactions and assigning oxidation numbers
  • Practice problems
  • Discussion of types of redox reactions (p. 139-145)

Homework: p. 162 #37, 40, 43, 44, 45, 47, 50, 54, 55 (PD), read p. 139-145

oxidation reduction reactions
Oxidation-Reduction Reactions
  • What was being transferred in acid-base reactions?
    • Protons!
  • Redox reactions: electron transfer!
2mg s o 2 g 2mgo s
2Mg(s) + O2(g)  2MgO(s)
  • Mg2+ bonds with O2-
  • What’s happening with electrons?
  • Two steps, 2 half reactions:

2Mg  2Mg2+ + 4e-

O2 + 4e-  2O2-

2Mg + O2 + 4e-  2Mg2+ + 202- + 4e-

2Mg + O2  2Mg2+ + 2O2-

2Mg2+ + 2O2-  2MgO

slide43

Oxidation: Half reaction that refers to the LOSS of electrons

  • Reduction: Half reaction that refers to the GAIN of electrons

2Mg  2Mg2+ + 4e-

O2 + 4e-  2O2-

  • Reducing agent: donates electrons
  • Oxidizing agent: accepts electrons
another example
Another Example
  • Zn(s) + CuSO4(aq)  ZnSO4(aq) + Cu(s)
  • (What type of reaction?)
  • For which elements is the charge different as a reactant and a product?
oxidation numbers
Oxidation Numbers
  • Keeps track of electrons in redox reactions
  • The number of charges the atom would have in a molecule (or ionic compound) if electrons were transferred completely.
assigning oxidation numbers
Assigning Oxidation Numbers
  • Free elements = 0 (ex: H2, Na, K, O2)
  • Monotomic ions = charge of ion (ex: Li+ = +1, Fe3+ = +3)
  • Oxygen = -2 (peroxide O22- = -1)
  • Hydrogen = +1, except with metals in binary compounds (ex: LiH) then = -1
  • Fluorine = -1
  • In a neutral molecule, sum must = 0
  • Not always integers
examples1
Examples
  • Li2O
  • HNO3
  • Cr2O72-
  • PF3
  • SO2
  • MnO4-
4 types of redox reactions
4 Types of Redox Reactions
  • Combination
    • S(s) + O2(g)  SO2(g)
  • Decomposition
    • 2HgO(s)  2Hg(l) + O2(g)
  • Combustion
    • C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(l)
  • Displacement
    • Three types…
three types of displacement
Three types of displacement
  • Hydrogen displacement
    • With alkali metals and some alkaline earth metals and cold water or HCl
    • 2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)
  • Metal displacement (use activity series)
    • TiCl4(g) + 2Mg(l)  Ti(s) + 2MgCl2(l)
  • Halogen displacement
    • F2>Cl2>Br2>I2 (moves down group 17)
    • Cl2(g) + 2KBr(aq)  2KCl(aq) + Br2(l)
classify and write oxidation s
Classify and Write Oxidation #s
  • 2N2O(g)  2N2(g) + O2(g)
  • 6Li(s) + N2(g)  2Li3N(s)
  • Ni(s) + Pb(NO3)2(aq)  Pb(s) + Ni(NO3)2(aq)
  • 2NO2(g) + H2O(l)  HNO2(aq) + HNO3(aq)
  • Fe + H2SO4  FeSO4 + H2
  • S + 3F2  SF6
  • 2CuCl  Cu + CuCl2
  • 2Ag + PtCl2  2AgCl + Pt
homework1
Homework
  • p. 162 #37, 40, 43, 44, 45, 47, 50, 54, 55 (PD)
14 oct 2010
14 Oct. 2010
  • Objective: SWBAT determine, from worked out examples, the process by which to solve molarity, dilution and gravimetric analysis problems.
  • Do now: For the following metal displacement reactions, determine if a reaction will occur. If yes, write the products:

Fe + CuSO4 

Ni + NaCl 

Li + ZnCO3 

Al + CuCl2 

agenda4
Agenda
  • Do now, homework
determining problem solving processes from examples
Determining problem solving processes from examples
  • With a partner, examine the first two examples for calculating molarity.
  • Determine and write out the steps to solve these problems.
  • Repeat for the second two examples (dilutions) and the final two (gravimetric analysis)
  • Then, solve the example problems on the back using your problem solving steps.