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COMPACT REGENTS REVIEW 2010-2011 MATTER Pure matter = substances, which are represented by (s), (l) or (g) Substances = elements (identical atoms) or compounds (fixed combinations of different elements) Compounds can be chemically decomposed, Elements cannot. Solution (aq) = homogeneous mixture = uniformly distributed substances in varying composition Filtration = method of separating heterogeneous mixtures Distillation = method of separating homogeneous mixtures using boiling point difference Chemical Change = atoms are rearranged = combustion or rusting Physical Change = the substance does not change, only the physical form of the substance ENERGY Potential Energy = energy of phase changes Highest Kinetic Energy = highest temperature Phase Change = no temperature change: q = m Hf (freezing / melting) or q = m Hv (boiling) Temperature Change: q = m x c x T (for water, c = 4.18 J/goC) Exothermic Changes: condensation (g l), freezing (l g), deposition (gs) Endothermic Changes: boiling (lg), melting (ls), sublimation (sg) Heating Curve plateaus = phase changes: PE increases, KE is constant Heating Curve slopes = temperature increases = KE increases ATOMIC STRUCTURE Subatomic Particles = protons, neutrons and electrons Orbital = 3D region outside of nucleus where electron is found 90% of the time Wave-Mechanical Model = most modern, the theory of electrons in orbitals Mass = p + n (Carbon-14 has a mass of 14, with 6 protons and 8 neutrons) Net Charge = p – e (An atom of Carbon-14 has a net charge of 0, 8 protons and 8 electrons) Nuclear Charge = p (Carbon -14 has a nuclear charge of +8) Isotopes of an Element = same # of protons, different # of neutrons Bright line spectra = spectral lines = light Light is produced when an electron transitions from higher to lower energy state Ground State Electron Configuration = found on Periodic Table: Mg 2 – 8 – 2 Excited State E.C. = an electron moved to a higher level: Mg 2 – 8 – 1 – 1 Average atomic mass = [(mass isotope #1) x (%) + (mass #2) x (%) + …] / 100% First subatomic particle discovered = electron Gold Foil Experiment conclusions: atom is mostly empty space with a massive (+) nucleus NUCLEAR CHEMISTRY Alpha particle 42He = most massive, positive, least energetic Beta particle 0-1e = negative Gamma ray 00y = massless, neutral, most energetic Transmutation = Nuclear Change Natural Transmutation = Decay = Table N = 1 reactant: 19779Au 0-1e + 19780Hg Artificial Transmutation = 2 reactants: 147N +10n 146C + 11p Radioisotope = unstable nucleus Atomic # 84 and above = only radioactive isotopes 1 ½ ¼ 1/8 = 3 half live events Half-Life Formula: # of decay events = time / half-life Medical isotopes = short half lives = 131I (thyroid) and 60Co (cancers) Dating Isotopes = long half-lives = 238U (rocks) and 14C (organic remains) Fusion = 21H + 21H 42He + energy = two smaller nuclei are fused together Fission = “division” = large nucleus is split into two smaller nuclei = 23592U + 10n 1 COMPACT REGENTS REVIEW 2010-2011 Mass Defect = the mass that seemed to be “lost” was converted into energy (fission and fusion) BONDING BARF = Break (bonds) Absorb (energy) , Release (energy) Form (bonds) Metallic Bonding (all metals) = valence electrons are mobile Covalent Bonding (all non-metals) = valence electrons are shared Polar Covalent = unequally shared (two DIFFERENT non-metals) Non-Polar Covalent = equally shared (two of the SAME non-metals) Ionic Bonding (metal + nonmetal) = valence electrons are transferred Most Polar Bond = biggest Electronegativity Difference (H – F) Most Ionic Bond = biggest Electronegativity Difference (Fr F) Metallic substances: high MP and BP, malleable, very conductive due to mobile electrons Molecular substances (covalent bonds): low MP, brittle solids, non-conductors Ionic substances: high MP, brittle, good conductors as (l) or (aq); non-conductors as (s) Oh, SNAP! Symmetrical Non-Polar, Asymmetrical Polar (for molecule polarity) Order of increasing intermolecular forces: (g) < (l) < (s) Order of increasing intermolecular forces: nonpolar molecules < polar molecules Order of increasing intermolecular forces: low melting/boiling pt < high melting/boiling pt PERIODIC TABLE Electronegativity = attraction for a pair of bonded electrons Ionization Energy = energy needed to remove a specific electron Metals: to the left of the staircase, including Al and Po. All solid except for Hg Metalloids: on the staircase: B, Si, Ge, As, Sb, Te, At: fair conductors but brittle Non-Metals: to the right: solids, liquids (Br2) and gases (H2, N2, O2, F2, Cl2 + noble gases) BrINClHOF: the seven diatomic elements All elements want to have Noble Gas Configurations: Mg (2-8-2) becomes Mg2+ (2-8) Neon! Metal atoms LOSE ELECTRONS to form smaller, positive ions Non Metal atoms GAIN ELECTRONS to form larger, negative ions Down a Group, elements get larger (more shells) and more metallic = lower IE and EN Across a Period, elements get smaller and less metallic = higher IE and EN Most metallic element = Fr = loses electrons most readily Leas metallic element = F = gains electrons most readily Allotropes = different forms of same elements with different structures and different properties Elements in same group = same # of valence electrons = similar chemical and physical properties Elements in same period = same # of occupied energy levels GAS LAWS Standard temperature = 273 K (0 oC) Standard pressure = 1 atm or 101.3 kPa Table H Normal Boiling Point = temperature where substance curve intersects dotted line (1 atm) Ideal gas molecules= no attractive forces = negligible volumes = large intermolecular distances Most Ideal Molecules = H2 and He Ideal conditions (think Summer) = high temperature, low pressure (except for Boranian, in summer school) As Pressure increase, Volume decreases (inverse relationship) P x V = constant As Temperature increases, Volume increases (direct relationship) V/T = constant Combined Gas Law: P1V1/T1 = P2V2 / T2 temperature is in Kelvin Equal Gas Volumes, Equal #’s of (moles of) gas molecules…at the same T and P 2 COMPACT REGENTS REVIEW 2010-2011 FORMULAS, EQUATIONS & MOLES A BALANCED EQUATION demonstrates the Law of Conservation of Mass: 2 H2 + O2 --> 2 H2O (NO ATOMS ARE CREATED OR DESTROYED) REACTIONS: SYNTHESIS: C + O2 --> CO2 DECOMPOSITION: CO2 --> C + O2 SINGLE REPLACEMENT: Element + Compound --> Element + Compound DOUBLE REPLACEMENT: Compound + Compound --> Compound + Compound WRITING FORMULAS FROM NAMES: Iron (II) Oxide --> Fe+2 O-2 --> Fe2O2 --> FeO Iron (III) Oxide --> Fe+3 O-2 --> Fe2O3 MOLECULAR formulas (C6H12) reduce to simplest whole-number EMPIRICAL formulas (CH2) mole formula: moles = mass / gram-formula mass Atomic Mass: The mass of ONE MOLE of an element (Carbon 12.011 grams / mol) Percent Composition formula: % = (mass of part / mass of whole) x 100% SOLUTIONS Characteristics: homogeneous mixtures; do not scatter light; do not settle on standing; cannot be separated by filtration; can have color In NaCl (aq) Solute: NaCl Solvent: H2O Gaseous solutes are more soluble at LOW TEMPERATURES and HIGH PRESSURES Solid & Liquid solutes are more soluble at HIGH TEMPERATURES. PRESSURE has no effect. Water is a POLAR MOLECULE: the hydrogens are (+) the oxygen is (-) Polar solvents (H2O) dissolve polar solutes (NH3) and ionic solutes (NaCl) Non-Polar solvents dissolve Non-Polar solutes Molarity Formula: Molarity = moles of solute / L of solution ppm Formula: ppm = (mass of solute / mass of solution) x 1,000,000 TABLE F is used to determine which IONIC SOLUTES are soluble in water TABLE G is used to determine if aqueous solutions are saturated, unsaturated or supersaturated KINETICS & EQUILIBRIUM The more effective collisions, the faster the reaction rate. The greater the surface area / concentration / temperature / pressure, the more effective collisions. IONIC reactants (NaCl + AgNO3) react faster than MOLECULAR ones (CH3OH +CH3COOH) Heat of Reaction (∆H) = potential energy of products - potential energy of reactants = the amount of energy absorbed (+) or released (-) in a reaction TABLE I gives the ∆H for a specific number of moles of product: H2 (g) + I2 (g) --> 2 HI (g) +53 kJ Producing 2 moles of HI absorbs 53 kJ of heat Catalysts increase reaction rate by lowering activation energy / providing lower energy pathway Catalysts have NO EFFECT on ∆H (heat of reaction) Activation Energy = HUMP of PE diagram - REACTANT line of PE diagram An EXOTHERMIC PE diagram has higher REACTANTS lower PRODUCTS An ENDOTHERMIC PE diagram has lower REACTANTS higher PRODUCTS Equilibrium exists only in CLOSED systems when... CONCENTRATIONS (masses) are CONSTANT RATES of forward and reverse reactions are EQUAL 3 COMPACT REGENTS REVIEW 2010-2011 In SATURATED solutions, the RATES of dissolving and crystallizing are EQUAL LECHATELIER’S PRINCIPLE: a system that loses equilibrium due to stress will shift to re-establish equilibrium STRESSES: change in temperature / change in concentration / change in pressure CATALYSTS speed up both forward and reverse reactions; have NO EFFECT on equilibrium Equilibrium SHIFTS AWAY FROM an increase in concentration or temperature (heat) Equilbrium SHIFTS TOWARDS a decrease in concentration or temperature (heat) When PRESSURE increases, equilibrium SHIFTS TOWARDS the side with fewer gas molecules ACIDS, BASES & SALTS Electrolytes (Acids, Bases and Salts) release ions in water, which then conduct electricity. The higher the concentration (M) of a solution with electrolytes, the more conductive. TABLE K: Common Acids = H with (TABLE E) ion or Group 17 Ion TABLE L: Common Bases = metal hydroxide or NH3 Salts are ionic compounds = metal + nonmetal Acidic solutions have pH < 7 / more hydronium than hydroxide / react with metals to form H2 (g) Basic solutions have pH >7 / more hydroxide than hydronium / react with fat to form soap In a pH of 1, the H3O+ concentration is 10-1 M In a pH of 13, the H3O+ concentration is 10-13 M Compared to a pH of 8, a pH of 2 is (8-2 = 6) 106 times more acidic Compared to a pH of 4, a pH of 6 is (6-4 = 2) 102 times less acidic TABLE M: BROMTHYMOL BLUE is yellow below 6.0 and above 7.6 is blue ARRHENIUS ACIDS release H+ as the only positive ion ARRHENIUS BASES release OH- as the only negative ion ACIDS are PROTON (H+) DONORS, whiles BASES are PROTON ACCEPTORS In NH3 + HCl --> NH4+ + Cl- The acids are HCl & NH4+ / The bases are NH3 & ClNeutralization reaction: Acid + Base ---> Salt + Water HCl + NaOH ---> NaCl + H2O Titration formula: Ma x Va = Mb x Vb (molarity of acid) x (volume of acid) = (molarity of base) x (volume of base) When a solution is neutralized in a titration, moles of OH- equal moles of H3O+ REDOX (or REDUCTION-OXIDATION) The sum of oxidation # in a formula must equal zero NaCl: (+1) + (-1) = 0 Na2S2O3: 2(+1) + 2x + 3(-2) = 0 oxidation # of sulfur = +2 Free elements have an oxidation # of zero A chemical reaction in which oxidation numbers change is REDOX A chemical reaction with a FREE ELEMENT is REDOX In the oxidation half-reaction, oxidation # increases as electrons are lost [OIL] Fe --> Fe+2 + 2e(0) = (+2) + (-2) In the reduction half-reaction, oxidation # is reduced as electrons are gained [RIG] Ag+ + 1e- --> Ag (+1) + (-1) = (0) for OXIDIZING / REDUCING AGENTS: ROA ORA as in “ROW”-a with the “OAR”-a R(OA) the Reduced is the Oxidizing Agent O(RA) the Oxidized is the Reducing Agent TABLE J: If the free metal is higher than the combined metal, the redox is spontaneous 3 Li + Al(NO3)3 --> 3 LiNO3 + Al If the free nonmetal is higher than the combined nonmetal, the redox is spontaneous F2 + 2 I- --> I2 + 2 FVoltaic Cell: spontaneous redox in which chemical reaction produces electricity (-)ANODE: where oxidation takes place...the metal HIGHER on Table J (AN OX) 4 COMPACT REGENTS REVIEW 2010-2011 (+)CATHODE: where reduction takes place...the metal LOWER on Table J (RED CAT) electrons flow from Anode to Cathode through the WIRE The SALT BRIDGE maintains electrical neutrality by permitting ion flow Electrolytic Cell: non-spontaneous redox in which electricity drives a chemical reaction Unlike the Voltaic Cell: (1) no salt bridge (2) requires a battery (3) cathode (-) & anode (+) Like the Voltaic Cell: (1) cathode reduction & anode oxidation (2) electrons flow from An to Cat 5