Chemistry Study Guide for Exam 3
Chemistry Study Guide for Exam 3 CHEM 1230-022
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This 15 page Study Guide was uploaded by Erika Scholl on Friday April 15, 2016. The Study Guide belongs to CHEM 1230-022 at University of Toledo taught by Terry Bigiono in Spring 2016. Since its upload, it has received 77 views. For similar materials see General Chemistry 1 in Chemistry at University of Toledo.
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Date Created: 04/15/16
General Chemistry Midterm Exam 2 Study Guide Conversions Ex) 355 km 10^3m 10^3s = 355 m S 1 km ms ms Empirical Formula is the smallest ratio of elements. Ex) C2 H3 O2 is empirical C4 H6 O4 is not empirical. 2 can be divided out of them all. Molecular formula is a multiple of the empirical formula. Ex) Limiting reactant NH3 + O2 NO + H2O NO is the limiting reactant. Percent Yield Actual yield * 100% Theoretical Yield What is the percent yield of H2O if 138g is produced from 16g of H2 and excess O2? 2H2 + 02 = 2H2O # g H2O = 16g H2 * 1 mol H2 * 2 mol H2O * 18.02g H20 = 143g H2O 2.02g H2 2 mol H2 1 mol H2O % yield = actual * 100% = 138g H2O *100% = 96.7% theoretical 143g H2O Formulas Grams given * 1 mol * 6.022x10^23 molecules = ?molecules Molar mass 1 mol Of element(s) XMass given * 1 mol of X * Ymoles given in formula * Grams of Y = Grams of Y Molar mass of X X moles given in formula 1 mol of Y Molarity = Moles of solute M = n n = v * M v = n Volume of solute (L) v M Molarity = mol M = mol L L Electrolytes are compounds that ionize and conduct electricity Strong acids and bases are strong electrolytes Weak electrolytes are: HF HCN C2H4O2 Soluble Elements and compounds Li Na K Rb Cs NH4+ NO3 ClO4 C2H3O2 SO4^2 except Sr^2+ , Ba2+ , Hg2^2+ , Pb^2+ Cl Br except Ag+ , Hg2^2+ , Pb^2+ I Oxidation: loss of one or more electrons Reduction: gain of one or more electrons Redox: electrons are transferred H2 S O4 2(+1) + ? + 4(2) = 0 net charge +1 ? 2 S = +6 (charges) Redox: hydrocarbon + 02(g) CO2(g) + H2O(l) Titration Net Ionic Equation Formulas for Wavelength, Energy, and Frequency: Wave length = Frequency = V Energy = E Planks constant = h h = 6.626x10^ 34 J*S Speed of light = c c = 3.00x10^8 m/s m = mass = c/v V=c/ E = h*V = h*c/ = h*c/E E=mc^2 Atomic Size of Elements Quantum Numbers Zeff = nuclear charge Zactual = number of inner electrons Zeff = Zactual – electron shielding Ex) Cl 17 protons – 10 electrons = +7 Cation is always smaller than the atom from which it was formed Anion is always larger Ionization energy = Ei1, Ei2, Ei3…… Ei2 is higher than Ei1… Lowest Ei values: group 1A (Alkali metals) Highest Ei values: group 8A (Nobel gasses) Ei values decrease going down within the groups. Covalent bond = sharing electrons and directional Ionic bonds= anions and cations and all directions Polar covalent = unequal sharing of electrons Resonance structures are multiple Lewis Structures for the same compound. Ex) Formal Charge = [# of valence e] – 1/2[# of bonding e] – [# of nonbonding e] Molecules are not flat, they have 3d shapes: for example H2O Elements and electron pairs are charge clouds, they want to repel each other and get as far away from each other as possible. Valence bond theory: quantum mechanical model that introduces the idea of combining orbitals to male chemical bonds. Sigma Bond: (σ bonds) are the strongest type of covalent chemical bond. They are formed by headon overlapping between atomic orbitals. Pi bond: (π bonds) are covalent chemical bonds where two lobes of one involved atomic orbital overlap two lobes of the other involved atomic orbital. Ch. 9. System: part of the universe we are studying. Surroundings: rest of the universe. Boundary: surface dividing the system and surroundings. Open systems: can exchange energy and matter. Closed system: matter only can exchange. Isolated system: no exchange. Open = glass of water. Closed = bottle water. Isolated = thermos. Internal energy depends on: chemical composition size of system temperature and pressure physical state Work: motion opposing a force w = F*d = m*g*change of heat (h) Heat: form of energy transferred as a result of a temperature difference between the system and the surroundings. Energy: capacity to do work. Work done on a system: positive = endothermic. Work done by a system: negative = exothermic. A state function is a property of something (like the change of energy), that only depends on the current state, not how it got there. Heat and work are NOT state functions! KE = 1/2mv^2 Kinetic energy = ½ mass * volume^2 Work = pressure * change in velocity W= P*change in velocity 1 law of thermodynamics Change in energy = q + w q = heat transferred Enthalpy(h) = energy + pressure*volume H= energy – work q = change in energy + pressure* change in pressure q = deltaE + pressure*deltaP Enthalpy is a state function! heat is heat leaving the system = exothermic +heat flows into the system = endothermic Thermodynamic state = 1 atm, 25 degrees C unless specified, 1M concentration is the most stable. Heat Capacity = (C) q = C*deltaT deltaT = q/C C = q/deltaT Extensive quantities: depend on extent and size of system (volume, C, mass, internal energy) Intensive quantities: does not depend on size and extent (temperature, pressure, density) Specific heat capacity: amount of heat needed to raise temperature of 1g substance by 1 degree C Molar heat capacity(cm): amount of heat needed to raise temperature of 1mol by 1 degree C. Heat of reaction values depend on: Molar quantities Physical state Pressure Temperature AA + BB = 2AB PE = bond energy DeltaE = Ep Er product reaction Hess’s law: deltaH does not depend on the path taken to synthetize a material. Bond Dissociation energy(D) = enthalpy change for bond breaking down. Spontaneous process proceeds on its own while a nonspontaneous process requires a continuous external influence to drive it. Entropy(S) has an absolute scale.
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