CHE 132 Aleks Notes PDF

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Notes on ALEKS objectives...

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Objective 1 Calculating entropy change (ΔS) using the Clausius definition - ΔS = Q/T - Q = enthalpy/heat in J or kJ - T = temperature in K Calculating absolute entropy (S) using the Boltzmann Hypothesis - S = KB ln(W) - KB = Boltzmann constant = 1.38065 x 10^-23 J/K - W = microstates (possible # of sites), no unit - S - units are J/K Calculating entropy change (ΔS) using the Boltzmann Hypothesis - ΔS = K Bln(W/W0 ) - KB = Boltzmann constant = 1.38065 x 10^-23 J/K - W = final # of microstates - W0 = initial # of microstates - S - units are J/K - Two molecules involved - If there are X sites for first molecule to bond to, there are then X-1 sites for the second molecule to bond to → therefore, there were X initial microsites and X(X-1) final microsites - Rotational kinetic energy - Think of how many ways energy can be split between the two molecules Predicting spontaneous change - Changes are spontaneous when the entropy of the universe (system + surroundings) increases - ΔSuniverse = ΔS + ΔSsurroundings - Note: ΔS = Q/T - S of both sys and surr increase → S of uni increase → spontaneous - S of both sys and surr decrease → S of uni decreases → nonspontaneous - One increases while other decreases → S of uni = ? → cannot determine spontaneity Predicting reaction entropy - Entropy increases when - Gases form from liquids/solids’ - Solutions/mixtures of gases are formed from pure substances - Moles of gases increase - So, entropy decreases when - Gaseous reactants produce liquids/solids - Pure substances form/precipitate from a solution - Moles of gases decrease Predicting how entropy changes with temperature and volume - T and V both increase OR one increases while the other stays constant→ S increases - T and V both decrease OR one decreases while the other stays constant → S decreases - One increases while other decreases → can’t tell how S changes

Predicting how entropy changes with mixing and separation under ideal conditions (constant temp and vol) - Entropy increases when pure substances are mixed - Entropy decreases when pure substances are formed/precipitate or separated/filtered from solution - Under nonideal conditions there is not enough info to determine change in entropy Writing standard formation reactions - Reactants are each separate element of the product in its standard form/state - Only 1 mole of product is formed, so reactants might have fraction coefficients Objective 2 No reaction goes 100% to completion - Equilibrium - rate of forward reaction is the same as the rate of the reverse reaction, amounts of reactants and products don’t change - The reactions haven’t stopped, they just cancel each other out - When reactants are added, forward reaction starts → products are produced, starting reverse reaction → goes back and forth until equilibrium General properties of equilibrium constants - Size of K tells whether reactants or products dominate at equilibrium - Large K (>10) → products - Small K ( 1 when dG is neg, E is pos - K < 1 when dG is pos, E is neg - Hint: look to K first Describing transition metals - Rare earth elements - lanthanides, Sc, Y, La - Transuranics - anything after U (uranium), radioactive and artificial - Noble metals - 8 metals in d block resistant to oxidation by acids, diagonal from Ru to Au - Coinage metals - used to make coins, Cu, Ag, Au Density of transition metal - Density increases as you go down a group - Density is highest around the middle of a transition series Typical metal ligands - Halogen anions - Molecular anions containing electronegative atoms (O, N, S, P) w/ lone pairs - OH-, NO2-, CO3 (2-), SCN- Small molecules containing electronegative atoms (O, N, S, P) w/ lone pairs - H2O, NH3, PH3 - Bidentate ligands - can form 2 coordinate covalent bonds per molecule, one bond per site - en, glyCoordination number - en forms 2 bonds - gly forms 2 bonds - EDTA forms 6 bonds Faraday constant - converting between C and mols - F = 96485 C/mol

Electrolytic cell - Reduction at cathode, oxidation at anode (same as galvanic cell) - Electrolysis of molten salt - liquid instead of aqueous ions/solid - Liquids normally would be gases Finding atomic radius from fcc or bcc lattice constant - Lattice constant (a) = width of a cell, side length - FCC - diagonal length is 4r - 4r = c in pythagorean theorem (c^2 = a^2 + a^2) - (4r)^2 = 2 a^2 - BCC - corner to corner length is 4r - 4r = c in pythagorean theorem (c^2 = a^2 + b^2 → c^2 = a^2 + 2a^2) - (4r)^2 = 3a^2 Calculating mass of electrolysis product from the applied current - Calculate moles of e- from current - Use mole ratio of e- to product to find moles of product products - Multiply by molar mass to get mass Objective 13 Naming complex ions with one type of ligand - (prefix + ligand)... (root w/ charge) - Ex: Cr(H2O)4Cl2 = tetraaquadichlorochromium(III) - OH (-) is hydroxo - CO3 (2-) is carbonato - Water = aqua - NH3 = ammine - CO = carbonyl - CN- = cyano Naming complex anions with one type of ligand - Change name of metal from -ium to -ate or adding -ate at the end - Fe = ferrate - Cu = cuprate - Mo = molybdate - Au =aurate Naming complex ions - Complex ligands - en - ethylenediamine - gly - glycinato - EDTA - ethylenediaminetetraacetate - Name of ligand already contains prefix → use Greek and put ligand name in parentheses - 2 bis, 3 tris, 4 tetrakis - Watch the charge of the entire complex and whether to use ium or ate

Naming coordination compounds - Names like ionic compounds Crystal field theory energy level diagram - Crystal field splitting - energy gap (delta) - P = energy required to pair up electrons in orbital - D > P - pair electrons before moving to higher level (low spin b/c less unpaired electrons) normal - D < P - put electron in each orbital before pairing (high spin b/c more unpaired electrons) - High or low spin - Stronger electric field = higher D = low spin - Weak field ligands = F, Cl, Br, H2O (high spin) - Strong field ligands = NH3, en, CN (low spin) - 4 ligands in tetrahedral → D < P, high spin Color and magnetic properties - E = hc / l - E = energy per photon in J - h = 6.6261 x 10^-34 Js - C = 2.99 x 10^8 m/s - L = wavelength in meters - Color of substance is opposite the color it absorbs

Drawing crystal field energy diagram - Find coordination number and ligand symmetry (molecular geometry) - CN = 6, octahedral CN = 4, tetrahedral CN = 4, square planar...