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					Reactions in Aqueous Solution
Chapter 4

A solution is a homogenous mixture of 2 or more substances

The solute is(are) the substance(s) present in the smaller amount(s) The solvent is the substance present in the larger amount
Solution Soft drink (l) Air (g) Soft Solder (s) Solvent H2O N2 Pb Solute Sugar, CO2 O2, Ar, CH4 Sn

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.

nonelectrolyte

weak electrolyte

strong electrolyte

Conduct electricity in solution? Cations (+) and Anions (-)

Strong Electrolyte – 100% dissociation NaCl (s)
H2O

Na+ (aq) + Cl- (aq)

Weak Electrolyte – not completely dissociated

CH3COOH

CH3COO- (aq) + H+ (aq)

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

d-

d+

H2O

Nonelectrolyte does not conduct electricity? No cations (+) and anions (-) in solution C6H12O6 (s)
H2O

C6H12O6 (aq)
Nonelectrolyte (NH2)2CO
CH3OH C2H5OH

Strong Electrolyte Weak Electrolyte HCl
HNO3 HClO4

CH3COOH
HF HNO2

NaOH Ionic Compounds

H2O

C12H22O11

Precipitation Reactions
Precipitate – insoluble solid that separates from solution
precipitate

Pb(NO3)2 (aq) + 2NaI (aq)

PbI2 (s) + 2NaNO3 (aq)

molecular equation Pb2+ + 2NO3- + 2Na+ + 2IPbI2 (s) + 2Na+ + 2NO3-

ionic equation Pb2+ + 2IPbI2 (s)

PbI2

net ionic equation Na+ and NO3- are spectator ions

Writing Net Ionic Equations
1. Write the balanced molecular equation. 2. Write the ionic equation showing the strong electrolytes 3. Determine precipitate from solubility rules 4. Cancel the spectator ions on both sides of the ionic equation Write the net ionic equation for the reaction of silver nitrate with sodium chloride.

AgNO3 (aq) + NaCl (aq)
Ag+ + NO3- + Na+ + Cl-

AgCl (s) + NaNO3 (aq)
AgCl (s) + Na+ + NO3-

Ag+ + Cl-

AgCl (s)

Solubility Rules for Common Ionic Compounds In water at 250C
Soluble Compounds
Compounds containing alkali metal ions and NH4+
NO3-, HCO3-, ClO3-

Exceptions

Cl-, Br-, ISO4
2-

Halides of Ag+, Hg22+, Pb2+ Sulfates of Ag+, Ca2+, Sr2+, Ba2+, Hg2+, Pb2+

Insoluble Compounds
CO32-, PO43-, CrO42-, S2-

Exceptions
Compounds containing alkali metal ions and NH4+

OH-

Compounds containing alkali metal ions and Ba2+

Acids
Have a sour taste. Vinegar owes its taste to acetic acid. Citrus fruits contain citric acid. React with certain metals to produce hydrogen gas. React with carbonates and bicarbonates to produce carbon dioxide gas

Bases
Have a bitter taste.
Feel slippery. Many soaps contain bases.

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

Arrhenius base is a substance that produces OH- in water

A Brønsted acid is a proton donor A Brønsted base is a proton acceptor

base

acid

acid

base

A Brønsted acid must contain at least one ionizable proton!

Monoprotic acids
HCl
HNO3

H+ + ClH+ + NO3-

Strong electrolyte, strong acid
Strong electrolyte, strong acid

CH3COOH

H+ + CH3COO-

Weak electrolyte, weak acid

Diprotic acids
H2SO4 HSO4H+ + HSO4H+ + SO42Strong electrolyte, strong acid Weak electrolyte, weak acid

Triprotic acids
H3PO4 H2PO4HPO42H+ + H2PO4H+ + HPO42H+ + PO43Weak electrolyte, weak acid Weak electrolyte, weak acid Weak electrolyte, weak acid

Neutralization Reaction
acid + base salt + water

HCl (aq) + NaOH (aq) H+ + Cl- + Na+ + OHH+ + OH-

NaCl (aq) + H2O Na+ + Cl- + H2O
H2O

Oxidation-Reduction Reactions
(electron transfer reactions) 2Mg (s) + O2 (g) 2MgO (s)

2Mg O2 + 4e-

2Mg2+ + 4e- Oxidation half-reaction (lose e-) 2O22Mg + O2 + 4e2Mg + O2

Reduction half-reaction (gain e-) 2Mg2+ + 2O2- + 4e2MgO

Zn (s) + CuSO4 (aq)
Zn Zn2+ + 2e- Zn is oxidized

ZnSO4 (aq) + Cu (s)
Zn is the reducing agent

Cu2+ + 2e-

Cu Cu2+ is reduced Cu2+ is the oxidizing agent

Copper wire reacts with silver nitrate to form silver metal. What is the oxidizing agent in the reaction?

Cu (s) + 2AgNO3 (aq)
Cu Ag+ + 1eCu2+ + 2e-

Cu(NO3)2 (aq) + 2Ag (s)
Ag+ is the oxidizing agent

Ag Ag+ is reduced


				
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