Chemistry Review (snc2dg)

Chemistry Separating Mixtures  Gravity: pour mixture into the funnel, which has cellulose filter paper o Mechanical mixtures with large particles are best suited o Long procedure, and does not remove dissolved materials o FILTRATE: items that passed through o RESIDUE: things that are caught by the filter  Vacuum: water aspirator creates low pressure necessary to draw mixture through filter paper, Bückner funnel, and into the sidearm flask  Distillation: heated solution, gases produced are condensed to form a liquid condensate o Boiling chips used to allow bubbles to form (surface of nucleation) o Condenser has cold water running up the outer tube o Gas produced is condensed by cold water, drips out on the other side o FRACTIONAL DISTILLATION: separate into distinct, multiple parts  Centrifugation: capsules with mixtures are spun inside the centrifuge, usually separates the suspension into a solid and a liquid o DECANT: pouring so that only a solid is left o PRECIPITATE: the solid that results o SUPERNATANT: the clear liquid that results from centrifugation  Separation funnel: a mixture of polar + non-polar substances; the stopcock is turned so that the bottom layer of the mixture will drip down, and closed when that layer nearly drains o Imprecise  Flocculation/coagulation: to separate a suspension of very fine particles, ALUM (aluminum potassium sulphate) and LIME (calcium hydroxide) react in the suspension to form a solid of FLOC (aluminum hydroxide); the fine suspended particles sink with the floc o Often used in water treatment  Chromatography: to break a mixture into its components (often pigments), a small sample is placed at the bottom of chromatography paper, and the rolled chromatography paper is then placed in water; highly soluble parts are carried high by the water, while less soluble parts appear lower o Used to compare composition

Diagrams  Lewis Dot diagrams for ions: o [Na+] indicates +1 charge, one electron lost o [ O -2] (8 dots around O) indicates full valence shell and -2 charge; superscript -2 and the square brackets are necessary to indicate that the element is charged

Ionic Bonds  OXIDATION NUMBER: no. of e- gained or lost by an atom in the formation of a chemical bond. o Positively charged ions: cations o Negatively charged ions: anions  Metal + non-metal elements transfer electrons to achieve a stable octet; the electrostatic attraction keeps them together  Names: o First word is the metal’s name (e.g. magnesium) o Second word is the –ide form of the non-metal’s name (e.g. bromide)  Ionic compound properties o Crystalline, brittle o Non-conductors of electricity o High melting points when solids  Variable valence metals o Multiple possible charges o Stock system  In parentheses after metal name, roman numerals indicate charge of metal (e.g. iron (II) oxide indicates that the iron has a charge of +2) o “ic-ous” system  Only for metals with 2 possible valences  –ic indicates the higher valence  –ous indicates the lower valence  Latin: cupr– (copper), ferr– (iron), plumb– (lead), stann– (tin), aur– (gold)  (e.g. ferric oxide indicates that iron has a +3 charge)

Covalent Bonds  Non-metal + non-metal share electrons to form a covalent bond (a molecular compound)  Names: o Prefixes indicate number of each element (e.g. dinitrogen tetroxide indicates 2 nitrogen atoms and 4 oxygen atoms)  Mono 1  Hexa 6  Di 2  Hepta 7  Tri 3  Octa 8  Tetra 4  Nona 9  Penta 5  Deca 10 o Mono is omitted for the first element if it has a subscript of 1 o Usually the atom with the greater bonding capacity is written first  Four valence electrons: bonding capacity = 4  Five valence: bonding capacity = 3  ...  Seven valence: bonding capacity = 1 o Second atom changes name to –ide o Exceptions:  Water (H2O)  Ammonia (NH3)

Polyatomic Ions  Important ones to know: o OH-1 hydroxide ion o SO4-2 sulphate ion +1 -2 o NH4 ammonium ion o SO3 sulphite ion + -1 (ammonia NH3 neutral plus H ) o CH3COO acetate ion o CO3-2 carbonate ion o Cr2O7-2 dichromate ion -1 -2 o HCO3 hydrogen carbonate ion o CrO4 chromate ion -1 (a.k.a. bicarbonate ion) o MnO4 permanganate ion -1 -1 o NO3 nitrate ion o CN cyanide ion (extremely soluble)  Negative polyatomics usually take place of non-metal in ionic bond

Acids/Bases  Acids = higher concentration of H+ ions  Characteristics:

 Bases = higher concentration of OH- ions

Acids Properties: − Sour taste − Water-soluble − Reacts with metals (to produce H2 gas) − Reacts with carbonates (to produce CO2 gas) − H+ ions are released in solution Examples: − HCl (toilet bowl cleaner – removes rust and scale [CaCO3 + MgCO3], pH control for pools, stomach acids) − H2SO4 (car batteries, industrial uses) − H3PO4 (coke, pepsi as flavouring) − CH3COOH (vinegar – food flavor, scale remover) − Citric acid (citrus fruits, flavouring)  pH = −log[H + ]  Strong acids o HNO3 nitric o H2SO4 sulphuric o HCl hydrochloric

Bases Properties: − Bitter taste − Water-soluble − Does not react with metals − Reacts with fats to break them down (produces soapy substance when in contact with skin or fats, can cause blindness if splashed in eye) − OH- ions are released in solution Examples: − Drain cleaner – NaOH − Baking soda − Cleaners – windex, etc − Soaps, medicine treatment for stomach − Hair dye − Bleach  [H + ] = 10−pH o o o

HClO3 HClO4 (HBr

chloric perchloric hydrobromic)

 Producing acids o Non-metal is burned in oxygen, product reacted with water  Carbon burned in oxygen to form carbon dioxide  Carbon dioxide gas dissolved in water makes carbonic acid o Two steps: 1) burn; 2) take the product and place it in water  Producing bases o Metals that displace H from H2O directly produce bases  Sodium(s) + Water → Sodium hydroxide(aq) + Hydrogen↑ o Metals below that line are burned, then reacted with water to form bases ∆

   

 Magnesium(s) + Oxygen → Magnesium oxide(s)  Magnesium oxide(s) + Water → Magnesium hydroxide(aq) Acids ionize Bases dissociate Neutralization o Acid(aq) + Base(aq) → Water(l) + a salt(aq) Indicators Indicator

Colour in Acid

Colour in Base

Colour in Neutral

red litmus paper blue litmus paper neutral litmus paper phenolphthalein bromthymol blue universal indicator purple cabbage juice

red red red clear yellow lighter orange/red red

blue blue blue fuchsia lighter blue (diluted) purple green

red blue purple clear lighter blue (diluted) diluted: lighter purple