Chapter5-2slides - 1 1 CHEM 1A03: Intro. Chemistry I Water...

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Unformatted text preview: 1 1 CHEM 1A03: Intro. Chemistry I Water & Aqueous Chemistry Ch.5: Reactions in Aqueous Solutions 2 Water: A Vital Natural Resource! Signifcance oF Water: Energy, Health & Environment No single measure would do more to reduce disease and save lives in the developing world than bringing safe water & adequate sanitation to all. UN Secretary-General Kofi Annan, 2003 International Year of Freshwater Water is probably the only natural resource to touch all aspects of human civilization from agricultural and industrial development to the cultural & religious values embedded in society. Koichiro Matsuura, Director-General, UNESCO 2 3 70% Earth surface is water 2% fresh water ( 0.6% accessible) Launch of Phoenix Mars Lander on Aug. 4, 2007 The River of Life: Water! Some Water Facts Earth Mars H 2 O Follow the water Search for water & life on Northern Plains of Mars 4 > 60% of total body mass & 90% human plasma is water (5 L) Born into Water: Sacs of Water Some Water Facts 1.1% Organic molecules ( e.g, Glucose) 0.9% Inorganic ions ( e.g., Na + ) 8% Protein ( e.g., Human Serum Albumin) 90% Water Content Plasma Composition Blood fractionation after centrifugation 3 5 Water: An Enigmatic Medium! Bulk Properties Essential to Life Unique Macroscopic Properties: 1. Unusually high boiling point (b.p.) of liquid water at STP bp = 100 o C at 1 atm (Sea level) T,P-dependent 2. Density of ice (0.92 g/mL) < liquid water (1 g/mL) at 0 o C Ice expands with freezing: Lower packing density 3 . High speciFc heat capacity of water (74 J/mol . K at STP) Absorbs thermal heat for storage/distribution/release 4. Water dissolves a variety of solutes as a solvent Strong solvation properties for most polar molecules/ions 41 Anomalies of Water: http://www.lsbu.ac.uk/water/anmlies.html 6 Water on the Brain?: Concept Check Which intermolecular force accounts for water s unusual high b.p.? (a) Ion-dipole (b) Dipole-dipole (c) H-bonding (d) Van der Waals (e) none of the above 4 7 Understanding Molecular Behavior! Molecular Properties of Water... Fig. 5-1, pg 143 8 Chemistry of Water Chemical Bonding & Geometry of H 2 O Two single covalent bonds + 2 n.b. lone e- pairs Distorted tetrahedral with bent molecular geometry H H O 104.5 o Covalent O-H bond Non-bonding e- lone pair 5 9 Polar covalent molecule: Large bond dipole moments ( ) = x d where , is fraction of charge and d is bond length, 1 Debye (D) = 3.34 x 10-30 C . m Chemistry of Water Inherent Polarity of H 2 O H 2 O electrostatic potential map High e- density Low e- density O H H ! + ! + !" Molecular Dipole Water 1.85 D 10 10 Strong intermolecular forces: H-bonding Covalent O-H: 492 kJ/mol VS H-bond O- -H: 23 kJ/mol They add collectively!...
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This note was uploaded on 06/18/2008 for the course CHEM 1a03 taught by Professor Landry during the Spring '08 term at McMaster University.

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Chapter5-2slides - 1 1 CHEM 1A03: Intro. Chemistry I Water...

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