lecture6 - Mon. Sept. 15, 2003 Todays Lecture Types of...

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Mon. Sept. 15, 2003 Today’s Lecture Types of Chemical Reactions and Solution Stoichiometry • 4.1 Water • 4.2 Aqueous Solutions • 4.3 Solution Compositions • 4.4 -4.9 Chemical Reactions
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Water , the common solvent: – molecular formula: H 2 O – molecular structure: – covalent bond: sharing of pair of electrons O H H Covalent bonds
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– sharing of electrons in each pair is not equal since oxygen is more electronegative (attracts electrons) than hydrogen. • electrons are attracted more towards oxygen • H becomes slightly +ve (+ δ ) and O gains a slight -ve charge (-2 δ ) • water is said to be “polar” – polar solvents such as H 2 O dissolve ionic solids by forming a shell around the ion: • this process is called hydration H O 2 δ - δ + δ + 105 ° H
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04_41 + + + + + + - - - - - - + + + + + - - - - - - O H H δ + δ + - O H H δ + δ + - + - - + Cation Anion Fig. 4.2
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– when ionic solids (salts) are dissolved in polar solvents such as H 2 O, they dissociate into anions and cations: H 2 O (NH 4 ) 2 SO 4(s) 2NH 4 + (aq) + SO 4 2- (aq) • this is true for most ionic compounds – water can also dissolve non-ionic compounds: • as long as they are polar • for example, ethanol – rule of thumb: “likes dissolves likes”
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• The nature of aqueous solution: – solute (compound) dissolves in a solvent • forms a solution – for aqueous solutions of ionic compound, the amount of dissolved ion is related to its electrical conductivity – classification of solutes in solutions: • strong electrolytes: conduct electricity efficiently • weak electrolytes: conduct only a small current • non-electrolytes: no current flow
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This note was uploaded on 01/16/2010 for the course CHEM CHEM 121 taught by Professor Peggy during the Spring '09 term at Simon Fraser.

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lecture6 - Mon. Sept. 15, 2003 Todays Lecture Types of...

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