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Hydrogen Bonding Interaction btwn e - -rich atom connected to H entity & another H attached to e — rich atom Interaction btwn e - -rich atom connected.

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Presentation on theme: "Hydrogen Bonding Interaction btwn e - -rich atom connected to H entity & another H attached to e — rich atom Interaction btwn e - -rich atom connected."— Presentation transcript:

1 Hydrogen Bonding Interaction btwn e - -rich atom connected to H entity & another H attached to e — rich atom Interaction btwn e - -rich atom connected to H entity & another H attached to e — rich atom e - -rich atom = O, F, N e - -rich atom = O, F, N Gives water > density than ice Gives water > density than ice –Ice floats Higher heat capacity Higher heat capacity

2 Hydrogen Bonding Unique properties Unique properties B.p. of H 2 O, HF, and NH 3 much higher B.p. of H 2 O, HF, and NH 3 much higher

3 Boiling Point Bp  temp. at which vapor pressure = external (atmospheric pressure) Bp  temp. at which vapor pressure = external (atmospheric pressure) At higher elevations atmospheric pressure is lower  water boils less than 100 °C At higher elevations atmospheric pressure is lower  water boils less than 100 °C

4 Surface Tension Outer molecules interact with surface, while inner interact with other molecules Outer molecules interact with surface, while inner interact with other molecules It has a “skin” It has a “skin” Skin toughness = surface tension Skin toughness = surface tension E required to break through surface E required to break through surface Smaller surface area reason that water drops spherical Smaller surface area reason that water drops spherical emo emo emo emo

5 Capillary Action When water goes up a small glass tube When water goes up a small glass tube Due to polarity of Si-O bonding with water Due to polarity of Si-O bonding with water Adhesive forces > cohesive forces of water Adhesive forces > cohesive forces of water Creates a chain or bridge Creates a chain or bridge Pulls water up tube Pulls water up tube Limited by balancing gravity with adhesive/cohesive forces Limited by balancing gravity with adhesive/cohesive forces Thus, water has a concave meniscus Thus, water has a concave meniscus

6 Mercury Forms a convex meniscus Forms a convex meniscus Doesn’t “climb” a glass tube Doesn’t “climb” a glass tube Due to cohesive forces > adhesive forces Due to cohesive forces > adhesive forces

7 Viscosity Hydrogen-bonding increases viscosity Hydrogen-bonding increases viscosity But large non-polar liquids like oil have: But large non-polar liquids like oil have: 1) large unwieldy molecules w/greater intermolecular forces 1) large unwieldy molecules w/greater intermolecular forces 2) greater ability to be entangled w/one another 2) greater ability to be entangled w/one another

8 Sublimation Going from solid to gas without going through the liquid state Going from solid to gas without going through the liquid state Enthalpy of sublimation =  H  sublimation Enthalpy of sublimation =  H  sublimation Iodine, dry ice (solid CO 2 ) & ice sublimate Iodine, dry ice (solid CO 2 ) & ice sublimate Frost on grass on a cold morning sublimates Frost on grass on a cold morning sublimates

9 Polymers Huge molecules with repeating monomers (subunits) Huge molecules with repeating monomers (subunits) Thermoplastics (polyethylene): respond to heating Thermoplastics (polyethylene): respond to heating Soften and flow when heated, harden when cooled Soften and flow when heated, harden when cooled Thermosetting plastics (Formica): initially soft, but solid when heated; irreversible Thermosetting plastics (Formica): initially soft, but solid when heated; irreversible

10 Disturbing chemical equilibria Le Chatelier’s Principle Le Chatelier’s Principle Change one component of the rxn, Change one component of the rxn, The rxn will attempt to rectify it The rxn will attempt to rectify it (rectify is not a bad word) (rectify is not a bad word) Think of it this way: Think of it this way: If something is changed, how can it be undone or controlled? If something is changed, how can it be undone or controlled?

11 Temperature variation on equilibrium 2NO 2(g)  N 2 O 4(g) + heat 2NO 2(g)  N 2 O 4(g) + heat Exothermic  heat out Exothermic  heat out Raise the temp to 298 K  will want to get rid of excess heat  will swing to left  producing more NO 2 (endothermic) Raise the temp to 298 K  will want to get rid of excess heat  will swing to left  producing more NO 2 (endothermic) Sooner or later, equilibrium re-established Sooner or later, equilibrium re-established

12 Pressure & volume change on equilibrium If volume decreased (pressure increased)  favors smaller # of molecules If volume decreased (pressure increased)  favors smaller # of molecules If volume increased (pressure decreased)  favors larger # of molecules If volume increased (pressure decreased)  favors larger # of molecules If reversible rxn has = # of molecules on each side, a volume/pressure change will do nothing If reversible rxn has = # of molecules on each side, a volume/pressure change will do nothing


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