experiment 8 power point presentation
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yASolution is a mixture of substances thathas a uniform composition; also known asHomogeneous mixtures.
yA Solution is made up of two components:y Solute- The substance dissolved in a solution;
and,
y Solvent- The substance that dissolves a solutein a reaction.
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y Solubility is the amount of substance thatdissolves in a given quantity of solvent at agiven temperature to form a saturatedsolution.
y Determines whether or not a solute willdissolve in a solvent, and to what extent it
will dissolve
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y Saturated- a solution in which undissolved anddissolved solutes are in equilibrium.
y
Supersaturated- are solutions with comparativelyhigher amount of solute than an equivalent saturatedsolution; solutions that contain greater amount ofsolute than what is needed to form a saturatedsolution.
y Unsaturated- a solution with lesser amt. of solutethan what is needed to form a saturated solution.
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y Nature of Solute and Solventy Polar solutes tend to dissolve in Polar solvents;
y Non-polar solutes are more likely to dissolve in
non-polar solvents.y The stronger the attractions between solvents
and solutes are, the greater solubility.
Note: opposite charges attract while molecules/ atoms withthe same charges are bound to repel each other
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y Experiment 8 procedure 1.1
y Place 2ml each of distilled water, ethanol, toluene in3 separate test tubes. Add to each solvent 0.5g NaCl.
Stir and shake each mixture and let stand. Repeatusing 0.5g naphthalene instead of NaCl. Recordresults as soluble, slightly soluble, or insoluble forsolid structures.
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Compound + NaCl Solubility
Water (H2O) Soluble
Ethanol (CH3CH2OH) Moderately/Slightly soluble
Toluene (C7H8) Insoluble
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y NaCl is Soluble in water because it dissociates in wateras Na+ and Cl- .y NaCl+ H2O Na+ + Cl- + H+ + OH-
y In this case, OH- ions bond with Na+ ions; while Cl- ions arecaptured by H+ ions. This manifests ion-dipole forces.
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y NaCl is SLIGHTLY soluble in Ethanol (ethyl alcohol)C2H5OH, because the structure of ethanol is slightlynon-polar at one end and polar at the other. The polar
group is the (-OH) that serves as ethanol's property asa solvent for polar substances such as salts. It does thisby using O- ions (of the (-OH)) to attract some of theNa+ ions, and its H+ to attract some of the Cl- ions.Because not all of the sodium chloride molecules arepulled apart, only a portion of NaCl moleculesdissolve. This is why sodium chloride is considered toslightly soluble in ethanol.
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yNaCl did not dissolve in toluene (C7H8),because toluene has no way of
dissociating NaCl molecules and bindingwith them this is because Toluene is astrong, non-polar molecule whereas NaClis a strongly Ionic and Polar compound,
so the action is repelling.
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Compound + Naphthalene (C10H8)
Water Insoluble
Ethyl Alcohol/ Ethanol Insoluble
Toluene Soluble
Molecular Diagram of Naphthalene,C10H8, a non-polar molecule
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y Basically, the results shown by using Naphthalene inreplacement of sodium chloride, show that non-polarmolecules are soluble in another non-polar molecules
as welly The Stability of the 2 carbon rings and strong Carbon-
Carbon Bond Linkages reasons out why Naphthalenecannot be dissociated using polar solvents such as
water and ethanol; the bonds created are too strong forwater and ethanol to come in between, but toluene, onthe other hand, does not break the bonds, instead,joins the 2-carbon rings.
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1.4
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Solvent Iodine Crystal
H2O Slightly clear; some particles
didnt dissolveH2O + KI Clear, particles dissolved
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y *from ion- dipole forces of intermolecularforces
y *a polar molecule
y *has an electrical dipole moment
y *universal solvent that dissolve salts, sugar
and some acids, alkalis and gases like oxygenand carbon dioxide
y *is tasteless and odorless
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y * from London dispersion forces (induceddipoles) of intermolecular forces
y * an electrostaticy *diatomic moleculey *soluble in watery *tend to interact viavan der Waals forces
y * 37 known (characterized) isotopes ofiodine, but only one, 127I, is stable.
y *a nonpolar molecule
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y *an ionic compound
y *white salt but can also be a viscous liquidand assumed as water
y *an ionic compoundy *a mild reducing agent
y *increase the solubility of iodine in water
because molecular iodine reacts reversiblywith the negative ion, generating thetriiodide anion I3
in equilibrium, which is
soluble in water
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y *substances with similar intermolecularattractive forces tend to be solute
y *a compound contains a basic anion (that is,the anion of a weak acid), solubility willincrease as the solution becomes more
acidicy *the solubility of slightly soluble salts
containing basic anion increases as H+increases (as pH is lowered)
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y*the smaller the molecules of the solute
are, the smaller is their molecularweight and size, the less difficult todissolve in solvent; smaller particles are
generally less soluble
yH2O= 5.685 x 10(exp 23) molecules
y I2= 3.01 x 10(exp 23) moleculesyKI= 6.02 x 10(exp 23) molecules
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2.1 To 4ml distilled water in a test tube,add benzoic acid crystals until only a few
crystals remain undissolved . record anychange in temperature duringdissolution of the solid as an increase, adecrease or no change.
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y For liquids and solid solutes,increasing the temperature not only
increases the amount of solute that willdissolve but also increases the rate atwhich the solute will dissolve.
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yFor some substances, heat is releasedwhen they dissolve in a given solvent.
The reaction is called exothermic.yFor some substances to dissolve in a
given solvent, heat is absorbed. The
reaction is endothermic.
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Though short of ionization, water
can hydrogen bond to benzoic acid.Thus
C6H5COOH + H2O ---> C6H5COO + H3O
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2.2 Heat the mixture and note any change in the amount of
undissolved solid while heating . Continue heating until all the
solid dissolves. Divide the hot solution into two portions. Cool one
portion in an ice bath. Leave the other in the test tube rack to cool.
Compare the size and shape of the crystals formed.
Table 2.2
amount size shape
Hot temperature Becomes lesser Becomes smaller Becomes circular
Roomtemperature
Greater than thesolution placed in
hot temp.
Bigger than thesolution placed inhot temperature
Irregular but closeto circular shape
Cool temperature Greater than roomtemperature
Bigger than inroom temperature
(froze)
irregular
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When the temperature of a system at equilibrium is increased, the
system reacts as if we added a reactant to an endothermic reactionor a product to an exothermic reaction. The equilibrium shifts in the
direction that consumes the excess reactant(or product), namely
heat.
Endothermic: reactants + heat products (heat absorbing)
Exothermic: reactants products + heat (heat-releasing)
C6H5COOH + H2O ---> C6H5COO + H + OH2
Endothermic: Increasing T results in an increse in KExothermic: Increasing T results in a decrease in K
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y We would like to thank everyone for listening to us, wehope we didnt bore you to death.
y Thanks to ourselves:y
Madelyn Palomares, for procedures 1.2 and 1.3y Allen Jane Manzano, for procedure 1.4
y John Christopher Morillo, for procedure 1.1 and Introduction
y Cris Adams Salgado, for step 2.1
y Sharmaine Sanchez, for step 2.2
And of course, acknowledgements to our ever-beautifulinstructor, Mrs. Melba Patacsil, for giving us time to presentthe subject matter.
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y http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THP-4JMRH9W-G&_user=10&_coverDate=03/31/1999&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=2ac5730ae42413b89de7cea3e4d6e572&searchtype=a
y Theodore Brown, Eugene Le May, Catherine Murphy. Chemistry The Central Science 11th Edition.2009. Pearson Education South Asia PTE. LTD, Philippines.
y
http://answers.yahoo.com/question/index?qid=20100522154504AAmLhQE
y http://wiki.answers.com/Q/Does_salt_dissolve_into_ethanol
y Microsoft Encarta 2009, Copyright Microsoft Incorporation
y http://www.hpwt.de/Chemie/Organike.htm