Water Water is perhaps the most important compound on our planet Water has several very important properties Surface tension* Adhesion/Cohesion* Freezing/Boiling* *All three are caused by hydrogen bonds Water is an excellent solvent!
Transcript
Slide 1
Water ZWater is perhaps the most important compound on our
planet ZWater has several very important properties ZSurface
tension* ZAdhesion/Cohesion* ZFreezing/Boiling* *All three are
caused by hydrogen bonds ZWater is an excellent solvent!
Slide 2
Hydrogen bonds ZAttractions between a hydrogen on one water
molecule and an oxygen on another water molecule Ocean water is a
solution in which many different substances are dissolved.
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Solutions ZSolutions form when one substance dissolves into
another ZMost solutions are water (aqueous) solutions ZAll
solutions have two parts The colored crystals are the solute, and
the clear liquid is the solvent.
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Parts of solutions ZSolvent: The dissolving medium (water is
the most common solvent). Usually more than 50% of the solution
ZSolute: The substance which actually dissolves (e.g. salt, sugar,
etc.). Usually less than 50% of the solution ZElectrolytes - form
ions in solution ZEx.: NaCl(aq); HCl(aq) ZNonelectrolytes - NO ions
in solution ZEx.: C 12 H 22 O 11 (aq)
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Electrolytes vs. Nonelectrolytes ZSubstances which produce
charged particles (ions) in solution are known as electrolytes.
ZNaCl (s) + H 2 O(l) --> Na + (aq) + Cl - (aq) ZCaCl 2 (s) + H 2
O(l) --> Ca +2 (aq) + 2Cl - (aq) ZNotice the mole ratio (# of
particles in solution) ZSubstances which produce uncharged
particles (molecules) in solution are known as nonelectrolytes. ZC
12 H 22 O 11 (s) + H 2 O(l) --> C 12 H 22 O 11 (aq) ZCompare the
# of particles in solution to an electrolyte.
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The Solution Process When an ionic solid, such as sodium
chloride, dissolves in water, the water molecules hydrate the
ions.
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The Effect of Particle Polarity on Solubility ZWater is a polar
molecule ZPolar molecules and ions can be effectively hydrated by
the water molecules ZSolutes which are nonpolar are generally not
effectively hydrated by water but can be effectively dissolved by
nonpolar solvents. ZExamples ZVitamins ZWater Soluble - C and all
the B vitamins ZFat Soluble - A, D, E, K
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Polarity and Solubility Oil spills can be contained to some
extent by using trawlers and a boom apparatus because oil and
water, having different polarities, are relatively insoluble in
each other.
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Types of solutions ZUnsaturated: contain less than the maximum
amount of solute ZSaturated: contain the maximum amount of solute
ZSupersaturated: contain more than the maximum amount of
soluteSupersaturated In a saturated solution, the dissolved solute
is in dynamic equilibrium with the undissolved solute.
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Solubility Rules ZThere are some general rules for the
solubility of ionic compounds (SALTS) in water. ZSoluble - the salt
is readily soluble in water ZInsoluble - the salt dissolves to such
a tiny extent that it is not possible to detect it with the naked
eye
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Solubility Rules
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ZSoluble it if contains: ZLi +, Na +, K +, NH 4 +, NO 3 -, C 2
H 3 O 2 - ZCl -, Br -, I - ZSO 4 2- ZInsoluble if it contains: ZAg
+, Pb 2+, Hg 2 2+ ZBa 2+, Pb 2+, Ca 2+, Sr 2+ ZOH -, CO 3 2-, S 2-,
PO 4 3-
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Identifying Precipitates in Reactions Where a Solid Forms ZAgNO
3 (aq) + KCl(aq) --> white solid ZKNO 3 (aq) + BaCl 2 (aq)
--> NR ZNa 2 SO 4 (aq) + Pb(NO 3 ) 2 (aq) --> white solid
ZKOH(aq) + Fe(NO 3 ) 3 (aq) --> white solid
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Writing DR equations ZAgNO 3 (aq) + AlCl 3 (aq) --> ZK 2 SO
4 (aq) + BaCl 2 (aq) --> ZNa 2 SO 4 (aq) + Pb(NO 3 ) 2 -->
ZKOH(aq) + Fe(NO 3 ) 3 (aq) -->
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Factors Affecting Solubility ZSolubility can be increased by
ZAGITATION ZSURFACE AREA OF SOLUTE ZBlock vs. powder ZTEMPERATURE
ZIncrease temperature for solid solutes (generally) ZDecrease
temperature for gaseous solutes ZPRESSURE (affects gaseous
solutes)
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Factors Affecting Solubility Temperature Effects Experience
tells us that carbonated beverages go flat as they get warm.
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Concentrated vs. Dilute Solutions
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Measurement of solution concentration Percent of solution m-m
m-v v-v Moles of solute per volume of solution Molarity (M) = mol
solute/liters soln M = mol/V
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Examples 1.Determine the molarity of a solution made by
dissolving 1.5 mol NaCl in enough water to make 0.45 liters.
2.Determine the molarity of a solution made by dissolving 12.5
grams of sodium hydroxide in 555 mL solution. 3.How many grams of
KCl are needed to make 2.5 liters of a 0.50 M solution? 4.Explain
how to make 0.500 L of 3.5 M NaOH.
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Molarity Practice 1.What is the molarity of 4.5 L solution
containing 14.3 moles of sodium chloride? 2.How many liters of a
0.25 M KOH solution can be made using 1.55 moles of solute? 3.How
many moles of Mg(NO 3 ) 2 are needed prepare 10.0 L of a 2.00 M
solution? 4.What is the molarity of a solution made by dissolving
13.7 g AlCl 3 in water to make 275 mL solution? 5.How many grams of
KMnO 4 are required to prepare 600.0 mL of 0.25 M KMnO 4 ? 6.What
volume of 0.075 M Ca(NO 3 ) 2 can be prepared with 10.4 g of the
solute?
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Dilutions When you add solvent to dilute a solution you do NOT
change the amount of moles of solute Remember, M = mol/V Moles
before(1) = Moles after(2) M 1 V 1 = M 2 V 2 Very useful in the lab
Frozen orange juice concentrate is diluted with water prior to
drinking.
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Dilution Examples 1.How much 12.0 M HCl is needed to prepare
250.0 mL of 2.5 M HCl? 2.If 130.5 mL of 2.00 M NaOH is diluted to
1.00 L, what is the molarity of the new solution? 3.How many moles
of NaOH are in the solution described above? 4.How would you
prepare 67.5 mL of 0.25 M K 2 CrO 4 using 6.0 M K 2 CrO 4 ?
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Solution Stoichiometry Balanced equations can be used to
predict the outcomes of reactions occurring in solution EX. 50.0 mL
of 1.5 M HCl reacts completely with 100.0 mL of 0.075 M NaOH. How
much NaCl can be formed?
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Solution Stoichiometry Barium chloride solution reacts with
sodium sulfate solution. What mass of barium chloride do you need
to prepare 10.0 mL of 0.05 M BaCl 2 ? What is the stoichiometric
equivalent (in grams) of sodium sulfate? How much precipitate can
be formed when mixing these two solutions?
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A water-antifreeze mixture has a higher boiling point and lower
freezing point than pure water.
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Colligative Properties Dissolved particles effect certain
properties of solutions These properties are affected by the AMOUNT
of solute particles 1.Concentration 2.Electrolytic nature of
solute
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Particle Effects Close-ups of the surface of a liquid solvent
before and after solute has been added.
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Colligative Properties 1. Freezing Point Depression 2.Boiling
Point Elevation 3.Osmotic Pressure - Osmotic pressure is the amount
of pressure needed to prevent the solution in the tube from rising
as a result of the process of osmosis.
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Osmosis and the effects of Osmotic Pressure Osmosis in Plants
The dissolved substances in tree sap create a more concentrated
solution than the surrounding ground water. Osmosis in Blood Cells
Reverse Osmosis Dialysis Hypertonic Hypotonic Isotonic