1 / 44

Mixtures

Mixtures. Mixtures are physical (NOT chemical) combinations Many mixtures have NO chemical reaction potential Sugar or Salt dissolved in water Solder, a mixture of Tin and Lead Unlimited number of potential combinations Some mixtures have chemical reaction potential

konane
Download Presentation

Mixtures

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mixtures • Mixtures are physical (NOT chemical) combinations • Many mixtures have NO chemical reaction potential • Sugar or Salt dissolved in water • Solder, a mixture of Tin and Lead • Unlimited number of potential combinations • Some mixtures have chemical reaction potential • Rocket Propellants (e.g. zinc + sulfur) • Mixture of oxidizer and combustible material • Gunpowder (Charcoal + Sulfur + Potassium Nitrate) • Stable for hundreds of years until ignited • Thermite (iron oxide + aluminum powder) • Reacts yielding liquid iron to weld railroad track • Hydrogen and Oxygen, gasoline and air • Requires an initiator (e.g. heat from spark or flame) • Other mixtures are inherently unstable • Metallic Sodium and water react violently • Liquid rocket propellants burn when mixed • Acids and Bases neutralize each other

  2. Compounds • Inorganic compounds, “entangled elements” • Chemical reaction creates bonding + heat energy • Constituents are no longer mechanically separable • Creation of a new material unlike the constituents • Gaseous hydrogen and oxygen burn to form liquid water • Metallic sodium and chlorine gas combine to form table salt • Law of Definite Proportions • Atoms usually combine in small integer multiples • Inorganic common ratios are 1 to 5 • NaCl, CaCl2, Al2O3, H2SO4, PCl5

  3. Molecules, Ions, Chemical Bonds • Ionic Bonds • Complete charge separation • Electrons relocated from donor to acceptor atoms • Unlike atoms involved (e.g. Sodium Chloride) • Opposite sides of periodic table • Dissolve in water to form charged ions • Ionic crystals formed when no solvent • Electrostatic “binding energy” holds crystal together • No distinct partnering • All Na and Cl ions are equivalent in solution or solid crystal • Neutral charge balance, but joined pairs of ions

  4. Molecules, Ions, Chemical Bonds • Ionic Bonds • “Cation” is positively charged ion • Attracted to “Cathode” which is negative pole • Typically a metal with 1-3 missing electrons • Na1+, Ca2+, Fe3+ • “Anion” is negatively charged ion • Attracted to “Anode” which is a positive pole • Typically a halogen or oxide with 1-2 extra electrons • F1-, Br1-, O2- … • Polyatomic Anions also very common • These are very stable molecular species • NO31-, SO42-, PO43-

  5. NaCl dissolving in waterEach ion “solvated” by water molecules, attracted to oppositely charged ends of water moleculesEqual numbers of Na+ & Cl- ions in solution

  6. Molecules, Ions, Chemical Bonds • Covalent Bond • Shared electrons between atoms • Pair of electrons involved, one from each atom • Same kind of atoms often linked to each other • Carbon-carbon electron sharing very common • Diatomic elements: O2, H2, N2, F2 … not He, Ne, Xe • “Octet Rule” describes stable configurations • Total of 8 electrons around atom most stable • Exception is Hydrogen = 2 for complete “s” shell • Can achieve an octet via sharing • My one + your one = two to share • Carbon is ideal candidate for sharing • 4 electrons to share with 4 other elements

  7. Molecules, Ions, Chemical Bonds • Why not diatomic He, Ne, Ar, Kr … ? • These already have a full octet • No need to share for 8 outer shell electrons • Full outer shell means INERT • No chemical reactions if no electrons to transfer • NO compounds form with He, Ne, etc. • Can ionize (remove electrons) with high voltage • Electrons fall back with emission of light • Low pressure Neon (pink) used in signs • Argon (blue) used in high power lasers • Xenon (white) for camera’s electronic flash

  8. Non-Metal Compounds • Many combinations involve Oxygen • CO2, NO2, SO2, etc. • Naming conventions • Non-oxygen element named first • If multiple atoms, use multiplier wording • Di, tri, tetra, penta, … (mono usually not used) • Oxygen next, with multiplier wording • Mono, di, tri, tetra, …. • A few examples • Carbon dioxide = CO2 • Carbon Monoxide = CO • Dinitrogen pentoxide = N2O5

  9. Nomenclature of multiple additions • Mono (one to add, “monogamous”, “monopole”) • Carbon Monoxide, is CO (C≡O) • Di (two to add, think “dipole”, “diode”) • Carbon Dioxide, is CO2 (O=C=O) • Tri (three to add, “trimester”, “triangle”, “tritium”) • Nitrogen Tri-Iodide, is NI3 • Tetra (4 to add, think “tetrahedron”) • Carbon Tetrachloride, is CCl4 • Penta (5 to add, think “pentagon”, “pentameter”) • Phosphorus Pentachloride, is PCl5 • Hexa (6 to add, “hexagon”, “hexagonal”) • Uranium Hexaflouride, is UF6

  10. Single Element Ions • Cations, positively (+) charged elements • From “cathode”, the negative battery pole • Positive (+) ions attracted to (-) cathode • Mostly metals which lost ≥1 electrons • Na+, Ca2+, Fe3+, etc. • Anions, negatively (-) charged elements • From “Anode”, the positive battery pole • Negative (-) ions attracted to (+) Anodes • Mostly non-metals which gained ≥1 electron • Cl-, Br-, O2-, etc.

  11. Why the terms “Cation”, “Anion” ?Cations (+) attracted to Cathode (-)Anions (-) attracted to Anode (+)

  12. What’s a Cathode …From the Greek work kathodos… “way down”Electrode where chemical reduction occurs, gain electrons.Cathodes emit electrons (diodes, CRT)

  13. Why is the electron negative ? • Benjamin Franklin responsible ! • Published kite in a storm experiment in 1780 • Nobody really knew what electricity was • A dangerous experiment, people killed repeating it • He applied terms “positive” and “negative” • “Electrical Fluid” was term used at the time • (+) and (-) Used for batteries, electrolysis • Unfortunately “positive” is backwards • Assumption of flow (+) to (-) was wrong • … but we kept the polarity definitions • Electrons go the other way, are therefore (-) • See wikipedia on Benjamin Franklin

  14. Element Ionic charges • Alkali metals (1st column) have single (+) charge • Na+, K+ , Li+ • Usually do NOT write the number for single charge • Alkalai Earth metals (2nd col.) have charge (+2) • Ca 2+ , Mg 2+ • Transition metals often have multiple valences • Iron can lose 2 or 3 electrons, Fe2+ or Fe3+ • Similar situation with Mn, Cr, Sn, etc. • Old Latin names indicated degree of valence • “-ic” at end was/is highest valence state (mostly) • But not always the same valence numerical value • Ferric is +3, Stannic is +4 • “-ous” at end was/is lowest valence state (mostly) • Not always the same numerical value

  15. Formation of Compounds • Binary Compounds • Cation + Anion  neutral molecule • Simple ratios = “law of multiple proportions” • Atom quantities must yield charge balance • 2 Fe3+ + 3 O2- Fe2O3 • H2SO4 2H++SO42- • Molecules must be “real” materials • Use multiplier to clear fractions (e.g. ½ O2)

  16. Naming Compounds • Binary Inorganic compounds • Compound name starts with an element name • Same names & symbols on periodic chart • Sodium (Na), Iron (Fe), Cadmium (Cd) • Cation element (+), then Anion (-) name • Chlorine, oxygen, sulfur • Anion (-) in binary compound ends in –ide • Sodium Chloride • Iron Oxide, • Cadmium Sulfide

  17. Binary Halogen Acids • For halogen acids, “hydro” is prefix used • Hydrochloric Acid = HCl • Avoids confusion with Chloric Acid = HClO3 • Binary Halogen Acids include • Hydrofluoric Acid = Hydrogen Fluoride = HF • Hydrochloric Acid = Hydrogen Chloride = HCl • Hydrobromic Acid = Hydrogen Bromide = HBr • Hydroiodic Acid = Hydrogen Iodide = HI

  18. Formula Writing • Cation first (usually a metal or hydrogen) • Hydrogen, H (valence +1) • Calcium, Ca (valence +2) • Aluminum, Al (valence +3) • Anion follows (often a halogen, or gas) • Sulfur  Sulfide (valence -2) • Chlorine  Chloride (valence -1) • Oxygen  Oxide (valence -2) • Add the two element names, formula is in atomic ratios • Hydrogen Sulfide, H2S ratio follows valence, 2:1 • Calcium Chloride, CaCl2 ratio follows valence, 1:2 • Aluminum Oxide, Al2O3 ratio follows valence, 2:3

  19. Formula Writing • Atomic ratios are simple numbers (1, 2, 3 …5) • Find a common denominator number for electrons • Multiply cation valence times anion valence • Aluminum (+3) * Oxygen (-2) = 6 total electrons involved • Divide each valence into the common denominator • 6/3 for aluminum = 2, • 6/2 for oxygen =3 • These values are the ratios of the elements • Al2O3

  20. Multi-Atom (poly atomic) molecules • Many Anion combinations involve Oxygen • Nitrite, NO21- Nitrate, NO31- • Sulfite, SO32- Sulfate, SO42- • Carbonate, CO32- BiCarbonate, HCO31- • Chlorate, ClO31- • Phosphate, PO43- …. And a lot more !

  21. Polyatomic Oxygen Anions • Oxygen forms group around other elements • 2, 3, 4 oxygen clusters surrounding another atom • Stable configuration due to electron sharing • Sharing fills outer electron (valence) shell • “Octet Rule”, 8 is “magic number” for full shells • Shells of 8 creates exceptionally stable configuration • Anion Groups exist with extra electrons • Gather as many as needed for full shells • “owning” or “sharing” electrons is equivalent • Sharing is as good as ownership ! • Excess electrons give ion a negative charge

  22. Polyatomic ions, +1 chargeTetrahedral ammonium: N has 5 electrons, H has 1, total = 9Total deployed is 8, so one “went missing”, charge is +1Hydronium is proton (+1) attached to water, O=6 elect, H=1, total =9 Total deployed is 8, so one “went missing”, ionic charge is +1

  23. Hydronium Ion

  24. Polyatomic Anions, -1 chargeFor NO31-, N has 5 electrons, O has 6, total is 18+5=23Total deployed = 24, so 1 extra electron = -1 chargeFor NO2-1, N has 5 electrons, O has 6, total is 12+5=17Total deployed = 18, so 1 extra electron = -1 charge

  25. Polyatomic Anions, -2 chargeFor SO42-, S has 6 electrons, O has 6, total is 5*6=30Total deployed = 32, so 2 extra electron = -2 chargeFor SO32-, S has 6 electrons, O has 6, total is 4*6 =24Total deployed = 26, so 2 extra electrons = -2 charge

  26. Preferred valence often the maximum • Nitrite would rather be Nitrate • NO2- adds 1 oxygen, N goes (+3)  (+5) • All valence electrons consumed at (+5) • Makes it useful as a preservative in sausage • Nitrite consumes oxygen before the meat does • Sulfite would rather be Sulfate • SO3- adds 1 oxygen, S goes (+4)  (+6) • All valence electrons consumed at (+6) • Also a preservative, used in wine • Sulfite consumes oxygen before the wine does • Prevents wine into vinegar (until sulfite runs out)

  27. Polyatomic Anions, CarbonateFor CO32-, C has 4 electrons, O has 6, total is 4+18=22Total deployed = 24, so 2 extra electron = -2 chargeFor HCO31-, C=4, 3O=18, H=1 so total =23Total deployed = 24, so 1 extra electron = -1 charge

  28. Polyatomic Anions, PhosphateFor PO43-, P has 5 electrons, O has 6, total is 5+24=29Total deployed = 32, so 3 extra electron = -3 chargeFor HPO42-, P=5 electrons, O=6, H=1, total is 5+24+1 =30Total deployed = 32, so 2 extra electrons = -2 charge

  29. Formula Writing • Polyatomic ions behave like other anions • Cl-1, NO3-1, SO4-2 • Use parenthesis around the polyatomic ion • Avoids confusion what multiple is involved • Ca(NO3)2 … not CaNO32

  30. Multiple Valence Cations • Some elements have multiple valences • Lose up to all electrons in outer shell • Old Latin names indicate valence • Fe++, Fe(II), or Ferrous versus Fe+++, Fe(III), or Ferric • Sn++, Sn(II), or Stannous versus Sn++++, Sn(IV) or Stannic • Mn++, Mn(II), or Managnous vs Mn++++, Mn(IV), or Manganic • Cr++, Cr(II), or Chromous versus Cr+++, Cr(III), or Chromic • Latin Names not precise • No valence numbers, only words • Numeric values inconsistent

  31. Oxides of Chlorine • Chlorine an unusual case, (+) or (-) valence • As halogen it exhibits (-1) charge • Due to gaining one electron to fill octet • Valence is -1 in HCl, Hydrochloric Acid • NaCl, CaCl2, AlCl3, etc. • Another possibility is to lose electrons • Relatively unstable and reactive compounds • 7electrons in outer shell, 5 more loosely held • Valence is +1 in HClO Hypochlorous acid • Valence is +3 in HClO2 Chlorous acid • Valence is +5 in HClO3 Chloric acid • Valence is +7 in HClO4 Perchloric acid

  32. More on Latin Names • xxx-”ic” acid yields xxx-”ate” anion • Nitric acid HNO3 yields nitrate ion, NO3- • Sulfuric acid H2SO4 yields sulfate ion, SO42- • Chloric acid HClO3 yields Chlorate ion, ClO3- • Originally the highest valence state observed • xxx-”ous” acid yields xxx-”ite” anion • Nitrous acid HNO2 yields nitrite ion, NO2- • Sulfurous acid H2SO3 yields sulfite ion, SO32- • Chlorous acid HClO2 yields chlorite ion, ClO2- • Originally the lowest valence state observed

  33. More on Latin Names • What to do after finding MORE valence states than handled by ”ous” and ”ic” suffixes? • Fix is more words to modify existing descriptors • “hypo” and ‘per” adopted to handle the situation • “Hypo”-xxx means 1 less oxygen (below “ous”) • Chlorous acid is HClO2 • Hypochlorous acid is HClO • Sodium Hypochorite (Chlorox) is NaClO • “Per”-xxx means 1 more oxygen (beyond “ic”) • Chloric acid is HClO3 • Perchloric acid is HClO4`

  34. What if it’s not in the text? • Look for “family” relationships in columns • Sulfur and Selenium have similar properties they are both in periodic chart column 6A • Sulfate is based on sulfur, SO4- - • Selenium analog is “Selenate” SeO4 - - • Tellurium analog would be “Tellurate TeO4- - • Cesium is similar to Sodium, in column 1A • Sodium Chloride is NaCl, • Rubidium analog would be RbCl • Cesium analog would be CsCl

  35. Los Alamos National Laboratory's Periodic Table

  36. Valence Naming Summary • Latin Names: Ferrous, Ferric, Chromic, .. • Good = easy to say and type • Bad = inconsistent, no numbers to rely on • Roman Numerals: Fe(III), Sn(IV) • Good = easy to type • Bad = clumsy to say, antiquated Roman Numbering • Plus and Minus signs : Fe++, SO4 - - • Good = intuitive, fast to hand write, clarity • Bad = inconvenient to type, clumsy for large valence values • Arabic character with sign: Fe2+ • Good = intuitive, clarity, good for large valences • Bad = inconvenient to type • Bottom Line … you will run into ALL of these • Be prepared !

  37. Stopping point for 32A • Now to the nomenclature dry lab • We’ll use OLD manual, $6.50 at bookstore • Inexpensive because we print it in-house • Page 58-69 in Fall 2009 edition • Pages 58-62 is background material • Pages 63-69 are the turn-in sheets • Work with partners, get a good start on each page so you know how to finish after lab. • Use Google, Wikipedia, other great web resources • Don’t copy from others, often a wrong answer source • Due next week

More Related