Lecture_6 - Today's Lecture Types of Chemical Reactions and...

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1 Types of Chemical Reactions and Solution Stoichiometry Today’s Lecture 4.1 Water, the Common Solvent 4.2 The Nature of Aqueous Solutions 4.3 The Composition of Solutions 4.4 Types of Chemical Reactions 1 4.5 Precipitation Reactions 4.6 Describing Reactions in Solution 4.7 Selective Precipitation 4.8 Stoichiometry of Precipitation Reactions (review on your own) Water, the Common Solvent ± why are aqueous solutions (solutions in which water is the dissolving medium) important? ± water is inexpensive and is abl et o dissolve a vast number of substances ± in aqueous solution, many substances are dissociated into ions, which can participate in chemical reactions ± aqueous solutions are found everywhere, from seawater 2 to living systems ± what happens when a substance dissolves in water?
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2 Water, the Common Solvent (cont’d) H O H ± an individual H 2 O molecule has a bent geometry ± the O-H bonds are covalent bonds ± electrons in each O-H bond are attracted more towards the oxygen atom 104.5 ± however, the pair of electrons in each of the O-H bonds of water are not equally shared between the two atoms (we’ll talk about why this is later) 3 ± hence, the O atom gains a slight excess of -ve charge (-2 δ ) and the H atoms become slightly +ve (+ δ ) ± note that δ denotes a partial charge ( less than one unit of charge ) Water, the Common Solvent (cont’d) ± because of this unequal charge distribution, water is said to be a polar molecule 4 ± Figure 4.2 shows a schematic diagram of polar water molecules interacting with the ions of a salt (a process called hydration), which assists in the dissolving process
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3 Water, the Common Solvent (cont’d) ± when an ionic compound dissolves in water, the ions are dispersed and are assumed to move around independently
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This note was uploaded on 06/27/2009 for the course CHEM CHEM 121 taught by Professor Peggy during the Spring '09 term at Simon Fraser.

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Lecture_6 - Today's Lecture Types of Chemical Reactions and...

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