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Reactions in Aqueous Solution. Chapter 4. Copyright © The McGraw-Hill Companies, Inc.  Permission required for reproduction or display. Solution. Solvent. Solute. A solution is a homogenous mixture of 2 or more substances.

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reactions in aqueous solution

Reactions in Aqueous Solution

Chapter 4

Copyright © The McGraw-Hill Companies, Inc.  Permission required for reproduction or display.

slide2

Solution

Solvent

Solute

A solution is a homogenous mixture of 2 or more substances

The solute is(are) the substance(s) present in the smaller amount(s) and is dissolved in the solvent

The solvent is the substance present in the larger amount and dissolves the solute

H2O

Soft drink (l)

Sugar, CO2

Air (g)

N2

O2, Ar, CH4

Pb

Sn

Soft Solder (s)

4.1

slide3

nonelectrolyte

weak electrolyte

strong electrolyte

An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity.

A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity.

4.1

slide4

H2O

NaCl (s)Na+ (aq) + Cl- (aq)

CH3COOHCH3COO- (aq) + H+ (aq)

Conduct electricity in solution?

Cations (+) and Anions (-)

Strong Electrolyte – 100% dissociation

Weak Electrolyte – not completely dissociated

4.1

slide5

A reversible reaction. The reaction can occur in both directions.

Ionization of acetic acid

CH3COOHCH3COO- (aq) + H+ (aq)

Acetic acid is a weak electrolyte because its ionization in water is incomplete.

4.1

slide6

d-

d+

H2O

Hydration is the process in which an ion is surrounded by water molecules arranged in a specific manner.

4.1

slide7

H2O

C6H12O6 (s) C6H12O6 (aq)

Nonelectrolyte does not conduct electricity?

No cations (+) and anions (-) in solution

4.1

precipitation reactions

precipitate

Pb(NO3)2(aq) + 2NaI (aq) PbI2(s) + 2NaNO3(aq)

Pb2+ + 2NO3- + 2Na+ + 2I- PbI2 (s) + 2Na+ + 2NO3-

Pb2+ + 2I- PbI2 (s)

PbI2

Precipitation Reactions

Precipitate – insoluble solid that separates from solution

molecular equation

ionic equation

net ionic equation

Na+ and NO3- are spectator ions

4.2

slide10

Solubility is the maximum amount of solute that will dissolve in a given quantity of solvent at a specific temperature.

4.2

writing net ionic equations

Write the net ionic equation for the reaction of silver

nitrate with sodium chloride.

Writing Net Ionic Equations
  • Write the balanced molecular equation.
  • Write the ionic equation showing the strong electrolytes completely dissociated into cations and anions.
  • Cancel the spectator ions on both sides of the ionic equation
  • Check that charges and number of atoms are balanced in the net ionic equation

4.2

practice problem
Practice Problem
  • Write the net ionic equation for the following reaction:
  • MgCl2(aq) + Na2S(aq)2 NaCl(aq) + MgS(s)
acids

2HCl (aq) + Mg (s) MgCl2 (aq) + H2 (g)

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

Acids

Have a sour taste. Vinegar owes its taste to acetic acid. Citrus

fruits contain citric acid.

Cause color changes in plant dyes.

React with certain metals to produce hydrogen gas.

React with carbonates and bicarbonates to produce carbon

dioxide gas

Aqueous acid solutions conduct electricity.

4.3

slide14

Bases

Have a bitter taste.

Feel slippery. Many soaps contain bases.

Cause color changes in plant dyes.

Aqueous base solutions conduct electricity.

4.3

slide15

Arrhenius acid is a substance that produces H+ (H3O+) in water

Arrhenius base is a substance that produces OH- in water

4.3

slide17

A Brønsted acid must contain at least one

ionizable proton!

A Brønsted acid is a proton donor

A Brønsted base is a proton acceptor

base

acid

acid

base

4.3

slide18

HCl H+ + Cl-

HNO3 H+ + NO3-

CH3COOH H+ + CH3COO-

H2SO4 H+ + HSO4-

HSO4- H+ + SO42-

H3PO4 H+ + H2PO4-

H2PO4- H+ + HPO42-

HPO42- H+ + PO43-

Monoprotic acids

Strong electrolyte, strong acid

Strong electrolyte, strong acid

Weak electrolyte, weak acid

Diprotic acids

Strong electrolyte, strong acid

Weak electrolyte, weak acid

Triprotic acids

Weak electrolyte, weak acid

Weak electrolyte, weak acid

Weak electrolyte, weak acid

4.3

slide19

HI (aq) H+ (aq) + I- (aq)

CH3COO- (aq) + H+ (aq) CH3COOH (aq)

H2PO4- (aq) H+ (aq) + HPO42- (aq)

H2PO4- (aq) + H+ (aq) H3PO4 (aq)

Identify each of the following species as a Brønsted acid, base, or both. (a) HI, (b) CH3COO-, (c) H2PO4-

4.3

neutralization reaction

acid + base salt + water

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

H+ + Cl- + Na+ + OH- Na+ + Cl- + H2O

H+ + OH- H2O

Neutralization Reaction

4.3

oxidation number
Oxidation number

The charge the atom would have in a molecule (or an

ionic compound) if electrons were completely transferred.

  • Free elements (uncombined state) and have an oxidation number of zero.

Na, Be, K, Pb, H2, O2, P4 = 0

  • In monatomic ions, the oxidation number is equal to the charge on the ion.

Li+, Li = +1; Fe3+, Fe = +3; O2-, O = -2

  • The oxidation number of oxygen isusually–2. In H2O2 and O22- it is –1.

4.4

slide22

Oxidation numbers of all the elements in HCO3- ?

  • The oxidation number of hydrogen is +1except when it is bonded to metals in binary compounds. In these cases, its oxidation number is –1.
  • Group IA metals are +1, IIA metals are +2 and fluorine is always –1.

6. The sum of the oxidation numbers of all the atoms in a molecule or ion is equal to the charge on the molecule or ion.

7. Oxidation numbers do not have to be integers. Oxidation number of oxygen in the superoxide ion, O2-, is -½.

HCO3-

4.4

practice problems
Practice Problems
  • Find the oxidation number for Nitrogen in the following compounds:
  • HNO3
  • Ca3N2
  • Mg(NO2)2
oxidation reduction reactions

2Mg 2Mg2+ + 4e-

O2 + 4e- 2O2-

2Mg + O2 + 4e- 2Mg2+ + 2O2- + 4e-

2Mg + O2 2MgO

Oxidation-Reduction Reactions

(electron transfer reactions)

Oxidation half-reaction (lose e-)

Reduction half-reaction (gain e-)

4.4

slide28

Steps for Determining Oxidation and Reduction

  • Assign oxidation numbers to each atom in the reaction.
  • Determine if an atom gains or loses electrons by comparing the oxidation number in the reactants to the oxidation number in the products.
  • If an atom loses electrons, then it is Oxidized OiL
  • If an atom gains electrons then it is Reduced RiG
  • Write each of the half-reactions.
slide29

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

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

Cu2+ + 2e- Cu

Copper wire reacts with silver nitrate to form silver metal.

What is the oxidizing agent in the reaction?

Zn Zn2+ + 2e-

Zn is the reducing agent

Zn is oxidized

Cu2+is reduced

Cu2+ is the oxidizing agent

4.4

types of oxidation reduction reactions

A + B C

2Al + 3Br2 2AlBr3

C A + B

2KClO3 2KCl + 3O2

Types of Oxidation-Reduction Reactions

Combination Reaction

+3

-1

0

0

Decomposition Reaction

+1

+5

-2

+1

-1

0

4.4

types of oxidation reduction reactions31

A + O2 B

S + O2 SO2

2Mg + O2 2MgO

Types of Oxidation-Reduction Reactions

Combustion Reaction

+4

-2

0

0

+2

-2

0

0

4.4

types of oxidation reduction reactions32

A + BC AC + B

Sr + 2H2O Sr(OH)2 + H2

TiCl4 + 2Mg Ti + 2MgCl2

Cl2 + 2KBr 2KCl + Br2

Types of Oxidation-Reduction Reactions

Displacement Reaction

+1

+2

0

0

Hydrogen Displacement

+4

0

0

+2

Metal Displacement

-1

0

0

-1

Halogen Displacement

4.4

slide33

M + BC AC + B

Ca + 2H2O Ca(OH)2 + H2

Pb + 2H2O Pb(OH)2 + H2

The Activity Series for Metals

Hydrogen Displacement Reaction

M is metal

BC is acid or H2O

B is H2

4.4

slide34

Cl2 + 2KBr 2KCl + Br2

I2 + 2KBr 2KI + Br2

The Activity Series for Halogens

F2 > Cl2 > Br2 > I2

Halogen Displacement Reaction

-1

0

0

-1

4.4

types of oxidation reduction reactions35

Cl2 + 2OH- ClO- + Cl- + H2O

Chlorine Chemistry

Types of Oxidation-Reduction Reactions

Disproportionation Reaction

Element is simultaneously oxidized and reduced.

+1

-1

0

4.4

slide36

NH3+H2O NH4OH

Classify the following reactions.

Zn + 2HCl ZnCl2 + H2

Ca + F2 CaF2

CaCl2 + Na2CO32NaCl + CaCO3

4.4

slide37

What mass of KI is required to make 500. mL of

a 2.80 M KI solution?

moles of solute

M = molarity =

liters of solution

Solution Stoichiometry

The concentration of a solution is the amount of solute present in a given quantity of solvent or solution.

4.5

practice problems38
Practice Problems
  • What mass of MgCl2 would you need to make 250.0 ml of a 6.50 M solution?
  • How much water would be needed to make a 2.0M solution given 96.0 g of NaCl?
  • How many grams of FeO are needed to make 500.00 ml of a 1.6M solution?
slide40

Moles of solute

before dilution (1)

Moles of solute

after dilution (2)

=

Dilution

Add Solvent

=

M2 V2

M1V1

Dilution is the procedure for preparing a less concentrated solution from a more concentrated solution.

4.5

slide41

How would you prepare 60.0 mL of 0.200 M

HNO3 from a stock solution of 4.00 M HNO3?

4.5

practice problem42
Practice Problem
  • How would make 250.0 ml of 2.00M HCl from a 12.0M stock solution?
slide43

Titrations

In a titration a solution of accurately known concentration is added gradually added to another solution of unknown concentration until the chemical reaction between the two solutions is complete.

Equivalence point – the point at which the reaction is complete

Indicator – substance that changes color at (or near) the

equivalence point

Slowly add base

to unknown acid

UNTIL

the indicator

changes color

4.7

slide44

WRITE THE CHEMICAL EQUATION!

What volume of a 1.420 M NaOH solution is

Required to titrate 25.00 mL of a 4.50 M H2SO4

solution?

H2SO4 + 2NaOH 2H2O + Na2SO4

4.7

practice problem45
Practice Problem
  • What volume of 2.0 M Mg(OH)2 is needed to titrate 20.0 ml of 1.0M H3PO4?