Chapter 4 chemical reactions
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Chapter 4 Chemical Reactions. HW #3 Due by Monday, 5/5/2014 HW #4 due by Friday, 5/9/2014 Quiz #2: Monday, 5/12/2014 Exam #2: Wednesday, 5/14/2014. End-of-Chapter Homework: pp 167 - 177. 5, 6, 9-11 14-18 19 (a,d,g,h) 28 29 31 32 333841 43

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Chapter 4 Chemical Reactions

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Chapter 4 chemical reactions

Chapter 4Chemical Reactions

HW #3 Due by Monday, 5/5/2014

HW #4 due by Friday, 5/9/2014

Quiz #2: Monday, 5/12/2014

Exam #2: Wednesday, 5/14/2014


End of chapter homework pp 167 177

End-of-Chapter Homework: pp 167 - 177

5, 6, 9-11 14-18 19(a,d,g,h) 28

29 31 32 333841 43

47 51 5557 59 61 65b 67

69 71 737981 8389 100


I solubility

I. Solubility

- Many Ionic compounds dissolve in water yielding ions.

-These soluble ionic compounds conduct electricity due to the ions. Are called electrolytes.

- Driving force is water being attracted to the ions, forming weak bonds, & releasing energy.

1) Nonelectrolyte (does not conduct electricity in water):

a) Molecular & Soluble - when dissolves, yields no ions - CH3OH

b) Ionic & Insoluble like AgCl or PbI2

2) Strong Electrolyte (Ionic, Soluble, Conducts well in water)

NH4Cl(s) -----) NH4+(aq) + Cl-(aq)

3) Weak Electrolyte (few % ionization in water; Weak Conductor)

NH3 + H2O ------) NH4+ + OH- (~ 1% ionized)

HC2H3O2 --------) H+ + C2H3O2- (~ 1 % ionized)


Chapter 4 chemical reactions

Svante Arrhenius

NaI in H2O – Soluble & Ionic; Many Ions

H2O – Molecular & No Ions

Nonelectrolyte – No Current

Electrolyte – Much Current


I solubility continued

I. Solubility Continued

  • Know general solubility rules : These allow you to predict both the solubility & products of many Reactions (Rxns).

    #1 Grp 1, NH4+, C2H3O2- &NO3- compds are soluble (except H).

    #2 Cl- Br- I-compds are solubleexcept : Ag+ Pb2+ Hg22+

    #3 SO4-2solubleexcept : Ca2+ Sr2+ Ba2+ Ag+ Pb2+ Hg22+

    #4 OH-compds are insolubleexcept#1 & Ca2+ Sr 2+ Ba 2+

    #5 Most CO3-2 (carbonates), PO4-3 (phosphates), & S-2 (sulfides) are insoluble except for #1, (rule 1).


Ii writing reactions ways to write example 1

II. Writing Reactions - Ways to write; Example 1

[Note: Ag ion is always Ag+1 does not need (I); Solvent is H2O]

silver nitrate + sodium chloride --------) silver chloride + sodium nitrate

1) Molecular Equation (ME):Write all as if not ionized

AgNO3(aq) + NaCl(aq) --------) AgCl(s) + NaNO3(aq)

2) Complete Ionic Equation (CIE):Write soluble,

ionic compounds as ions; should use subscripts like (aq)

Ag+ + NO3- + Na+ + Cl- ----) AgCl(s) + Na+ + NO3-

3) Net Ionic Equation (NIE):Eliminate Spectator Ions

Ag+(aq) + Cl-(aq) -----) AgCl(s)


Iii reaction types a precipitation reactions

III. Reaction Types A. Precipitation Reactions

- Formation of an insoluble compound (precipitate, ppt) is a driving force in a chemical reaction.

- Can predict a product from the solubility rules.

Method:Write soluble ionic reactants as ions. Check solubility rules & see if insoluble product forms from ions.

Example: Predict product when mix K2SO4(aq) & BaCl2(aq) Write CIE & NIE.

2K+ + SO42- + Ba2+ + 2Cl- ---) BaSO4(s) + 2K+ + 2Cl-(CIE)

Ba2+(aq) + SO42-(aq) -----) BaSO4(s)(NIE)


Iii reaction types b acid base rxns

III. Reaction Types B. Acid-Base Rxns

1. Definitions(Note: Proton = H+)

Arrhenius:Acid =substance which releases H+ in water.

Base =substance which releases OH- in water.

Examples: HCl(aq) -----) H+(aq) + Cl-(aq)

NaOH(aq) -----) Na+(aq) + OH-(aq)

Bronsted-Lowry:Acid = Proton Donor

Base = Proton Acceptor

Example:(air is the solvent)

NH3(g) + HCl(g) -----) NH4Cl(s)


Iii reaction types b acid base rxns1

III. Reaction Types B. Acid-Base Rxns

2. PropertiesNote: salt = any ionic compound

Acids: - Sour taste

- Turn Indicator dyes a specific color:

Phenolphthalein colorless; Litmus red

- React with bases to yield salt + H2O

Bases:- Bitter Taste, Feel Slippery

- Turn Indicator dyes a specific color:

Phenolphthalein red; Litmus blue

- React with acids to yield salt + H2O

- Strong Acids/Bases ionize 100% in water

- Weak Acids/Bases ionize < < 100% in water


Iii reaction types b acid base rxns2

III. Reaction Types B. Acid-Base Rxns

3. Examples (Know these strong & weak acids & bases)

Strong Acids:HCl HBr HI HNO3 H2SO4 HClO4

Strong Bases: NaOH KOH Ba(OH)2 (but not too sol.)

Example in water: HCl(aq) -----) H+ + Cl-100% to the right

Weak Acids: HF HC2H3O2 HCN H2CO3

Weak Bases:NH3[= NH4OH (in water)]NaHCO3

Examples in water: NH4OH NH4+ + OH-~1% to the right

HC2H3O2H+ + C2H3O2-~1% to the right


Iii reaction types b acid base rxns3

III. Reaction Types B. Acid-Base Rxns

4. Acid-Base or Neutralization Reactions

- Acids react with bases to give: salt(ionic compd) + H2O

- Driving force is to produce stable H2O& sometimes a gas.

- Examples:NaOH + HF -----) NaF + H2O

2KOH + H2SO4 ---) K2SO4 + 2H2O

  • Some Neutralization Rxns produce a gas:(memorize these six)

    H+ + HCO3- -----) CO2(g) + H2O

    2H+ + CO32------)CO2(g)+ H2O

    2H+ + SO32- -----) SO2(g) + H2O

    2H+ + S2- -----) H2S(g)

    H+ + CN- -----) HCN(g)

    NH4+ + OH------) NH3(g)+ H2O


Iii reaction types b acid base rxns4

III. Reaction Types B. Acid-Base Rxns

5. Write three rxn formats (ME, CIE & NIE) for reaction of potassium hydroxide with hydrochloric acid:

ME:KOH + HCl -----) KCl + H2O

CIE:K+ + OH- + H+ + Cl- -----) K+ + Cl- + H2O

NIE:H+(aq) + OH-(aq) -----) H2O(l)

Note: 1) The above net ionic equation is common for many acid-base reactions. The production of stable H2O is a driving force for the reaction.

2) H+ in water is better represented by H3O+

3) H3O+is a polyatomic ion = hydronium ion


Iii reaction types b acid base rxns5

III. Reaction Types B. Acid-Base Rxns

5. ME, CEI and NIE

- Write the ME, CIE & NIE for: HCl + NaHCO3(in water)

ME: HCl + NaHCO3 -----) NaCl + H2O + CO2

CIE: H+ + Cl- + Na+ + HCO3- ---) Na+ + Cl- + H2O + CO2

NIE: H+(aq) + HCO3-(aq) -----) H2O(l) + CO2(g)

6. Titration - Process of adding known (amount & concentration) of Base (or Acid) in a burette to an unknown concentration of Acid (or Base). End point is determined with an indicator or a pH meter. Can now determine the amount of the unknown (quantitative analysis).


Iii reaction types b acid base rxns6

III. Reaction Types B. Acid-Base Rxns

Known M & Volume

(Standard Solution)

+ indicator

After titn can calculate moles & M.


Iii reaction types c predicting products review

III. Reaction Types C. Predicting products - Review

  • Predicting products:write a) strong acids & b) solubleionic reactants as ions; look to see if the ions can form:

    (1) aprecipitate(solubility rules)

    (2) agas(six gas equations)

    (3) anonionized molecule like H2O or HC2H3O2

  • Write NIE (in water) for: 1) BaI2 + AgNO3 & 2) HCl + NaCN

    1) Ba+2 + I- + Ag+ + NO3- -----) AgI(s) + Ba+2 + NO3-

    Ag+(aq)+ I-(aq) -----) AgI(s)(Balanced NIE)

    2) H+ + Cl- + Na+ + CN- -----) HCN(g) + Na+ + Cl-

    H+(aq) + CN-(aq) -----) HCN(g)(Balanced NIE)


Iii reaction types d redox rxns

III. Reaction Types D. Redox Rxns

1. Definitions & Introduction:

- Oxidation Reduction Reaction (Redox Rxn) is one in which electrons are transferred.

- Oxidation = Loss of Electrons

- Reduction = Gain of Electrons

2. Examples: (Note: electrons lost & gained must be same)

2Mg + O2 -----) 2MgO

[ 2Mgo ---) 2Mg2+ + 4e- = Oxidation ] Half Rxn

[ O2o + 4e- -----) 2O2- = Reduction ] Half Rxn

3Cu+2 + 2Al -----) 3Cu + 2Al+3

[ 2Alo -----) 2Al+3 + 6e- = Oxidation] Half Rxn

[ 3Cu+2 + 6e- -----) 3Cuo = Reduction] Half Rxn


Iii reaction types d redox rxns1

III. Reaction Types D. Redox Rxns

Note: Oxidizing agent causes oxidation

Reducing agent causes reduction

3. Uses of RedoxRxns:a) Create new chemicals

b) Theoretical Importance (chem 123)

c) Battery – allow the e’stransferred to perform work

4. Oxidation Numbers (ON):

Definition:ON = the charge that an atom or group of atoms would have if they were ionic.

Uses:1)Redox Rxn(ID & what’s been oxid/red & #e-)

2) NomenclatureFeF2 = Iron(II)Fluoride; (II) = ON

3) Used in balancing redox rxns(chem 123)

Rules: Know the following rules [Order gives priority]


Iii reaction types d redox rxns2

III. Reaction Types D. Redox Rxns

5. Rules for Determining ON (Know)

Note: When is a conflict, 1st rule controls result.

a) The sum of ON’s add up to give the charge

b) The ON of a neutral element by itself is 0

c) Group 1, 2, 13 ions are +1, +2 & +3 respectively;

(exception: H is -1 when combined with metal: KH , NaH)

d) F is -1

e) O is -2 (exception: O is -1 when found as a peroxide, O22-)

f) Cl, Br, I are -1 [when together like BrCl, most electronegative = -1]


Iii reaction types d redox rxns3

III. Reaction Types D. Redox Rxns

Examples:Determine the ON of single N in each:

N2 N3-1 Na3N N2O NO NF3 NO2 NO3-1

0-1/3 -3 +1 +2 +3 +4 +5

- Which of the above forms of N can explosively react with organics? Why?

- Determine ON of each atom in FeSO3(Note: SO3-2 ON = -2)

[+2 +4 -2]

  • Which are redox: (ones with change in ON; ∆ON)

    1) Mg + Cl2 -----) MgCl2

    2) CH4 + 2 O2 -----) CO2 + 2 H2O

    3) HCl + NaOH -----) H2O + NaCl


Iii reaction types d redox rxns4

III. Reaction Types D. Redox Rxns

6. Redox Reaction Types

Combination: 2Al + 3F2 -----) 2AlF3

Decomposition: 2HgO -----) 2Hg + O2

Combustion: CH4 + 2O2 -----) CO2 + 2H2O

Single Replacement:2Na + 2HCl -----) 2NaCl + H2

[ Can predict reaction from table 4.6, Pg 153;

The more active metal will replace the cation ]

7. Balancing redox rxns: Can become difficult; so, rules were generated & will cover in Chemistry 123.


Iv quantitative aspects of solutions

IV. Quantitative Aspects of Solutions

A. Molarity, M

- Many reactions take place in solution & we need a

way to measure concentration; Mis common way.

- M = moles of Solute M = m(use as eqn)

L Solution L

solvent = substance present in largest amount solute = substances dissolved in solventsolution = solute + solvent (everything present)

B. Molarity Calculations

1) Calculate the M if 4.5 moles of HCl are dissolved in a total volume of 500 mL (0.500 L)

M = m = 4.5 moles = 9.0 mHCl = 9.0 MHCl L 0.500 L L


Iv quantitative aspects of solutions1

IV. Quantitative Aspects of Solutions

2) Calculate M if 0.020 g of CaCO3 are dissolved in 40 L

a) convert g CaCO3to mols; b) plug into M eqn; M = m/L

0.020 g CaCO3 x 1 mole CaCO3/100. g CaCO3 = 2.0x10-4 mol CaCO3

M = moles = 2.0x10-4 mol CaCO3 = 5.0x10-6M CaCO3

L 40 L

3) How many moles of HCl are present in 2.0 L of 0.30 MHCl? M = moles/Lmoles = M x L

moles= 0.30 m HCl x 2.0 L = 0.60 moles HCl

L

4) How many L of 12 MHCl will provide 2.0 moles of HCl ?

M = m L = m = 2.0 mole HCl = 0.17 L HCl

LM 12 mole/L


Iv quant aspects of solutions c dilution problems

IV. Quant. Aspects of Solutions C. Dilution Problems

- Frequently we are given a concentrated solution & we need to add solvent to get a more dilute solution. This is a dilution problem.

M1 x V1 = M2 x V2 Note: 1) Initial moles = Final moles

2) Works with any conc. or vol. units

3) Use eqn ONLY for dilution problem

Example: How many mL of 12 M HCl are needed to make 100. mL of 3.0 M? M1 x V1 = M2 x V2

V1 = M2 x V2= (3.0 M x 100. mL) = 25 mL

M112 M

- Take 25 mL of 12 M HCl and add enough water to make 100 mL.


Iv quantitative aspects of solutions2

IV. Quantitative Aspects of Solutions

D. Gravimetric Analysis - A type of analysis where one converts the analyte to an insoluble compound which is then isolated, dried & weighed.

Example: A 1960 dime (2.50g) is dissolved in nitric acid. HCl is then added to form insoluble AgCl, which is collected, washed, dried & weighed. Calculate a) the g of Ag & b) w/w % Ag in the dime if 2.98 g of AgCl was obtained.Ag ---) Ag+1 ---) AgCl

a) g Ag in dime:

2.98 g AgCl 1 mol AgCl 1 mol Ag 108 g Ag = 2.25 g Ag

143 g AgCl1 mol AgCl1 mol Ag

b) % Ag in dime:

w/w % Ag = g Ag x 100%= 2.25 g Ag x 100% = 90.0%

g Dime 2.50 g


Iv quantitative aspects of solutions3

IV. Quantitative Aspects of Solutions

E. Volumetric Analysis

- An analysis technique where the M & volumeof a reagent in a burette is used to calculate the mols or M of an unknown.

- NOTE: This is a typical stoichiometric problem except that we calculate mols of reagent from M & Linstead of from grams.

Example: 25.0 mL of HCl is titrated with 45.5 mL of 0.433 MNaOH. Calculate the a) mols of HCl present & b)M of the original HCl.

1 HCl + 1 NaOH -----) 1 NaCl + 1 H2O

a) m 0.433 m NaOH 0.0455 L NaOH 1 m HCl = 0.0197 m HCl

L NaOH 1 m NaOH

b) M = moles HCl = 0.0197 m HCl = 0.788 M HCl

L 0.0250 L


E vol anal example note hc 2 h 3 o 2 ha mw 60 05 g m

E. Vol Anal, Example: Note HC2H3O2 = HA, MW = 60.05 g/m

1) Moles HA (12.1 mL NaOH = 0.0121 L)

0.500 m NaOH x 0.0121 L = 0.00605 m NaOH

L

0.00605m NaOH x 1m HA/1m NaOH = 0.00605 mHA

2) M HA(10.0 mL HA = 0.0100 L HA)

M= m = 0.00605 m HA = 0.605 m/L HA

L 0.0100 L HA

3) w/w % HA = (g HA / g Soln) x 100%

g HA = 0.00605m x 60.05 g/m HA = 0.3633 g HA

w/w% HA = (0.3633g HA /10.3 g soln) x100 = 3.53%


General example

General Example

  • Give the NIE for reaction of Lead (II) Nitrate with hydroiodic acid.

    Pb(NO3)2 + HI ----)

    Pb+2 + NO3- + H+ + I- ----) PbI2(s) + H+ + NO3-

    Pb+2(aq) + 2I-(aq) ----) PbI2(s)

    -? Mols PbI2 from 0.10 m HI. 0.10 m I-1 m PbI2 = 0.050 m PbI2

    2 m I-

    - ? Mols PbI2 from 2.0 L of 0.050 m/L HI?

    0.050 m HI 2.0L 1 m PbI2 = 0.050 m PbI2

    L 2 m HI


Chapter 3 4 review

Chapter 3 & 4 Review

  • Mole

  • % Composition

  • EF & MF

  • Stiochiometry: Reg, LR, Amt. Left, % Yield

  • Predicting Products: Solubility, Gas, H2O & Weak Acids

  • Writing Rxns: ME CIE NIE Phases

  • Electrolytes

  • Acids & Bases

  • RedoxOxidation & Reduction

  • ON

  • MM & Stiochiometry & Titrations; Dilution


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