experiment 8 power point presentation

8/3/2019 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

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