Chemistry 152 Notes


As I develop my study guide for general chemistry, I will place general items of interest on this page. These are excerpts from the general chemistry study guide that I am currently writing. Please be warned that converting the formatted text to HTML format results in the loss of symbols (such as delta signs) and super and subscripting. Therefore, this material may be hard to follow in places. Also, I have purged the example problems in this version to conserve on space.


Chapters 11 and 12

Chapters 13-15

Chapters 16 and 18

Chapter 19

Main Group Elements

     -    Periodic Trends

     Increase Going from Left to Right

          -    Nuclear charge
          -    Ionization energy
          -    Electronegativity
          -    Nonmetallic character

     Decrease Going from Left to Right

          -    Metallic character
          -    Atomic radius

     Increase Going Down a Column

          -    Metallic character
          -    Atomic radius

     -    Bonding

          -    Metals tend to form ionic compounds with
               nonmetals

          -    Nonmetals tend to form covalent
               compounds with other nonmetals

     Metals

          -    Typically solids
          -    "Shine"
          -    Malleable
          -    Good conductors (heat, electricity)
          -    Low ionization energy
          -    Low electronegativity
          -    Form cations easily
          -    Hydrides are ionic
          -    Oxides are ionic and basic

     Nonmetals

          -    All physical states represented
          -    Lack luster
          -    Brittle
          -    Poor conductors
          -    High ionization energies
          -    High electronegativity
          -    Form anions
          -    Hydrides are covalent
          -    Oxides are covalent and acidic

     -    Second Row Elements

          -    Only the s and p orbitals are available for
               bonding

          -    Allows for sigma and pi bonding (review
               this)

          -    All are relatively small and somewhat highly
               electronegative

          -    All form a maximum of 4 bonds

     -    Group 3A Elements

          -    Primary oxidation state is +3 (ns2np1)

          -    Going down a column ... metallic character
               increases

          -    Larger elements also have the possibility for
               a +1 state

     Boron

          -    Obtained from Borax, Na2B4O710H2O

          -    Pure boron has high MP and relatively inert

          -    Used in making high strength composites
               (addition of boron fibers)

     Boron Compounds - Covalent Bonding

     -    Halides (BCl3, BF3)

          -    B is sp2 hybridized
          -    Behaves as Lewis acids, the B has an empty
               p orbital

     -    Hydrides

          -    Normally called boranes
          -    Very volatile
          -    Very good reducing agents
          -    H transfers as hydride
          -    B is sp3 hybridized
          -    Geometries are roughly tetrahedral
          -    Simplest compound BH3 is actually a dimer
               B2H6
          -    Forms a 3-center, 2-electron bond ... the
               bridging bonds have been shown to be
               longer

     -    Group 4 Elements

          -    Metallic character increases going down the
               column

          -    Most common oxidation state is +4 (ns2np2)

          -    As size increases the possibility for +2
               increases .... +4 forms covalent bonds and
               +2 forms ionic bonds

     Carbon

          -    One of the most versatile elements
          -    May use sp3, sp2, or sp hybridizations
          -    Allows for sigma and pi bonding
          -    Three forms known:

               -    Diamond (sp3 network)
               -    Graphite (sp2 network)
               -    Fullerenes, spherical network, C60 or
                    larger

     Carbon Compounds

          -    Will only look at general classes

               -    Oxides
               -    Carbonates
               -    Cyanides
               -    Carbides

          -    Will look at the larger groupings when we
               take up organic chemistry in chapter 23

     -    Carbon Oxides (CO and CO2)

          -    Preparation

               CO
                    2 C + O2    2 CO

               CO2
                    2 CaCO3   CaO + CO2
               Fermentation
                    C6H12O6   2CH3CH2OH + 2 CO2

     Carbon Monoxide

          -    Used to prepare methanol
          -    Colorless, odorless, very toxic
          -    Hemoglobin binds very tightly with CO
               (more so than with oxygen)
          -    Low concentrations may cause symptoms

     Carbon Dioxide

          -    Colorless, odorless, nontoxic
          -    Used to fight fires, carbonation, refrigerant

     Carbonates

          -    NaCO310H2O, washing soda, basicity of the
               carbonate ion makes it a good choice for
               cleaning purposes

          -    NaCO3, soda ash, glass making

          -    NaHCO3, baking soda, reacts with acidic
               soda to produce CO2, causes dough to rise

     Cyanides

          -    Referred to as a pseudohalogen because the
               ion reacts like a halogen

          -    A primary use is in the recovery of metals
               (Ag and Au) from ores

          -    Lewis base, will react with acids to form
               HCN which is extremely toxic

     Carbides

          -    Carbon has a negative oxidation state in
               these cases

          -    CaC is used in the production of acetylene
               and is prepared by heating CaO with C

          -    SiC is also referred to as carborundum,
               second in hardness to diamond and has a
               diamond-like structure

          -    Excellent industrial abrasive

     Silicon

          -    Compounds containing this element make
               up about 990% of the earth's crust

          -    Most common form, SiO2 (quartz, sand)

          -    Pure silicon has a diamond-like structure
               and in ultra-pure formed used as a
               semiconductor (less than 1 ppb of
               impurities)

     Silicates

          -    Basic building blocks, SiO44-, and Si2O76-

          -    ZrSiO4 (Zircon) is a good example

          -    In nature the more highly bridged species are
               present (Si2O64-)

          -    Beryl (Be2Al2Si6O18) ... if Cr3+ is present the
               gem is green (emerald)

     Germanium, Tin, Lead

          -    Relatively low natural abundances

          -    Extracted from ore:
               -    SnO2, cassiterite
               -    PbS, galena

          Uses:

          -    Ge: semiconductor, same general structure
               as diamond
          -    Pb: electrodes, paints, pipes
          -    Sn: bronze (Sn, Cu); pewter (Sn, Pb, Cu);
               solder (Sn, Pb)

     -    Group 5 Elements

          -    N, P, As, Sb, Bi
          -    Show the expected trends going down a
               column
          -    Maximum oxidation state +5, min -3
               (ns2np3)
          -    N, P include all possible oxidation states
          -    Middle elements ... +5
          -    Lower elements .... +3

     Nitrogen

          -    Colorless and odorless at room temperature
          -    Makes up about 78% of the atmosphere (by
               volume)
          -    Uses: inert atmosphere, refrigerant,
               precursor for fertilizers
          -    Decreased reactivity is due to the strong N-N triple bond
          -    reactions usually involve high temperatures
               and high pressures

                         N2 + 3 H2    2 NH3

     Nitrogen Compounds

          -    Ammonia, NH3
               -    Precursor for fertilizers
               -    Weak base
               -    sp3 hybridized N
               -    BP -33, may be used as a solvent
               -    Yields ammonium salts upon reaction
                    with acids

                         HCl + NH3     NH4Cl

          -    Hydrazine, N2H4

               -    Prepared by reacting ammonia with
                    hypochlorite ion

               -    This is why you don't want to mix
                    bleach and ammonia
               -    Colorless poisonous liquid that can be
                    used as rocket fuel

          -    Nitrogen Oxides

               -    N2O, NO, NO2

               -    N2O: laughing gas, used to dispense
                    whipped cream

               -    NO: prepared by oxidizing ammonia
                    with oxygen on an industrial scale

               -    Precursor for the prep of nitric acid;
                    also known to protect the heart from
                    low oxygen levels by widening the
                    blood vessels

          -    Nitrogen Acids

               -    Nitrous, HNO2, and nitric, HNO3

               -    Nitrous acid is used in organic
                    reactions, Sandmeyer

               -    Nitric acid is used in the production of
                    fertilizers such as NH4NO3; it's also
                    classified as a strong acid and oxidizer

               -    Will dissolve most metals (including
                    gold)

     Phosphorous

          -    This is the most abundant of the group 5
               elements in the earth's crust ... mostly found
               in phosphate rock, Ca3(PO4)2

          -    Sixth most abundant element in the body
               (bones, tooth enamel)

          -    Preparation: heat phosphate rock, carbon,
               silica at 1500C

          -    P is one of the top industrial chemicals ...
               fertilizers, food additives, acid prep,
               detergents

          -    Two forms: white (toxic, tetrahedral, bursts
               into flames when exposed to air, reactive);
               red, (more stable, less reactive, not as toxic)
     Phosphorous Compounds

     -    Phosphine, PH3

          -    Colorless, poisonous gas, poor proton
               acceptor (not as basic as ammonia), easily
               oxidized

          -    Industrial uses: preparation of phosphoric
               acids, ligands for catalysts

     -    Phosphorous Halides

          -    Prepared by reacting halogens with
               phosphorous

          -    These compounds are used as reagents to
               form other halogenated species

          -    Will react readily with water to hydrolyze to
               phosphoric acid (even moisture in the air
               will react)

     -    Phosphorous Oxides

          -    React with water to form acids
          -    Look at structures of H3PO3, and  H3PO4 and
               show that one is diprotic and the other is
               triprotic

     -    Group 6A Elements

          -    O, S, Se, Te, Po
          -    Exhibit the same trend going down a column
               (O,S nonmetal; Se, Te semiconductor; Po
               metal)
          -    The outer shell is 2 electrons shy of an octet
               ... -2 is a common state.  As
               electronegativity decreases higher other
               states are possible (+4,+6)

          Sulfur

          -    Sixteenth most abundant element in the
               earth's crust

          -    Commonly present as sulfide or sulfate
               (PbS, galena; HgS, cinnabar; CaSO4,
               gypsum)

          -    Sulfur may be recovered from oil gas by
               reacting H2S with SO2 to yield S and water
          -    elemental sulfur forms S-S bonds to form 8-membered rings, rhombic sulfur

          -    Heating this causes smaller chains to form
               (melts)

          -    Cooling the mixture causes a rubbery solid
               to form, plastic sulfur .... actually a polymer

     -    Sulfur Compounds 

     H2S

          -    Colorless gas that smells like rotten eggs, is
               actually very toxic

          -    Can be detected by smell at very low
               concentrations ... overwhelms ability to
               smell quickly

          -    May be prepared by reacting FeS with acid
               or by hydrolysis of thioacetamide

          -    This is how you prepared in lab ... [H2S] was
               kept very low in this manner

     Sulfur Oxides

          -    SO2, SO3 
          -    Typical acidic properties expected for oxides
               of nonmetals
          -    Used to prepare H2SO4 which is one of the
               most important industrial chemicals
          -    Strong, oxidizing acid
          -    Uses: fertilizers, refining, paints, explosives,
               batteries, rubber

     -    Group 7A - Halogens

          -    Common oxidation state .. -1 (ns2np5)
          -    May exist in positive states when forming
               halic acids (+1,+3,+5,+7)
          -    Example: chloric acid, perchloric acid ...
               HClO3, HClO4 (+5,+7)
          -    These are all strong oxidizers
          -    Only the chlorinated analogs have been
               isolated in pure form
          -    Chlorate salts are also strong oxidizers and
               should be handled with care
          -    Uses: weed killers, rocket fuels,, bleach,
               water purification
          -    Examples: NaOCl, NH4OCl4 

Chapter 22

Chapter 23