PHA 611 LEC Summary of 2nd Shifting Lectures PDF

Note: This summary of lectures is based on the graded recitation. CHEMICAL KINETICS (10%) Rate law expresses the rate of a particular reaction. CHEMICAL EQUILIBRIUM At chemical equilibrium, rate forward = rate backward (or reverse). Law of Mass Action states that the equilibrium constant...

Note: This summary of lectures is based on the graded recitation. CHEMICAL KINETICS (10%) Rate law expresses the rate of a particular reaction. CHEMICAL EQUILIBRIUM At chemical equilibrium, rate forward = rate backward (or reverse). Law of Mass Action states that the equilibrium constant (Kc) depends on both reactant and product equilibrium concentrations as well as the coefficients of the concentrations. All constants are temperature-dependent. Kc is not affected by (1) initial reactant and product concentrations, (2) changes in pressure (for gas molecules), and (3) addition of a catalyst. Forward reaction favors the formation of product concentrations. Backward / reverse reaction favors the formation of reactant concentrations. Kp constant is the equilibrium constant for gas species since they rely on pressure instead of molarity concentrations. ○ Higher pressure = Lower volume: Shift to lesser no. of gas moles ○ Lower pressure = Higher volume: Shift to greater no. of gas moles Homogeneous equilibrium is when reactant and product species have the same phase or state of matter. Otherwise, it is a heterogeneous equilibrium (different phases). Formulas for getting Kc: ○ Kc = [product conc.] / [reactant conc.] ○ Kc = Rate forward / Rate backward To get the Kc value of multiple equilibria: Kc = Kc’ x Kc’’ x Kc’’’... Kc is not equal to Qc because the reaction quotient (Qc) is dependent on the initial concentrations of the species, while the equilibrium constant (Kc) is dependent on the equilibrium concentrations of the species. IONIC EQUILIBRIA Arrhenius theory (aka Water theory) explains that acids liberate H+ or H3O+ ions, while bases liberate OH- ions in aqueous solutions. Bronsted and Lowry theory is a PROTONIC concept. It explains that acids are proton donors while bases are proton acceptors. Lewis theory is an ELECTRONIC concept. It explains that acids are electron acceptors while bases are electron donors. Lewis theory also explains the concept of electrophiles and nucleophiles, which is based on the amount of electrons they have. ○ Electrophiles are “electron loving” since they are a poor species (of electrons). Acids are electrophiles. ○ Nucleophiles are rich species (of electrons). Bases are nucleophiles. Lewis Acids are usually metals, or ions that are positively charged (cations). Lewis Bases are usually nonmetals, or ions that are negatively charged (anions).  Strong electrolytes are strong conductors of heat and electricity. They completely dissociate in water (100%) and are in irreversible reaction. Examples of these are strong acids (SA), strong bases (SB), and salts. Weak electrolytes are partially ionized in water and are in reversible reaction (equilibrium). Examples of these are weak acids (WA) and weak bases (WB). Non-electrolytes usually consist of organic compounds (e.g. hydrocarbons) and carbohydrates (e.g. glucose). Conjugates are ionized species. To get the conjugate of an acid or a base: ○ Conjugate Acid (CA) - Add 1 H+ ion to the substance ○ Conjugate Base (CB) - Remove 1 H+ ion to the substance. In organic compounds, we can determine their acidity strength based on EDGs and EWGs of organic compounds. ○ Electron-donating groups (EDG) - lowers acid strength. Examples include -CH3, -NO2, -CN, and -COOH. They ○ Electron-withdrawing groups (EWG) - increases acid strength. Examples include -OH, -NH2, and alkyl groups. ○ Ex. Which of the following is the strong acid? Lactic acid (C3H6O3) Benzoic acid (C6H5COOH) Trichloroacetic acid (CCl3COOH) Acetic acid (CH3COOH) pH and pOH formulas: pH = -log[H+] and pOH = -log[OH-] are only applicable for strong acids and bases, respectively, based on Arrhenius theory. The higher the Ka, the lower the pKa. The formula for pH and pOH for both strong and weak acids is: ○ pH = -log√KaCa ○ pOH = -log√KbCb The formula for percent ionization is: ○ % ionization = (√KaCa / Ca) x 100% Salts containing small, highly-charged cations produce acidic salts after dissociation. Salts of Weak Acids and Weak Bases ○ Ka = Kb; Neutral Salt ○ Ka > Kb; Acidic Salt ○ Ka < Kb; Basic Salt ACID-BASE AND SOLUBILITY EQUILIBRIA Buffer solutions resist changes in PH (changing the pH by only 1 unit). Buffer capacity is the strength of resistance in pH changes. Solubility product constant (Ksp) is not equal to equilibrium constant (Kc). Complex ions, or coordination compounds, are ions with a central metal cation bonded to one or more molecules or ions called ligands. ○ Coordination number refers to the total number of atoms, ions, or molecules bonded to the atom in question. ○ Ligands are ions or neutral molecules that bond to a central metal atom Formation constant (Kf), or stability constant, is directly proportional to the stability of the complex ion.