Ba(OH)2 DEMO: Added H2O on wood block. Ba(OH)2(s) + NH4SCN(s)  2NH3(g) + 2H2O(l) + Ba(SCN)2(s). This is a spontaneous endothermic reaction. The water on the block froze so the beaker was frozen to the block. This rxn is product-favored (ΔG°<0). Burning methane DEMO: The rxn is product-favored (exothermic), but it’s slow at room temperature, and faster at higher temperature. It’s not spontaneous b/c CH4 is in the presence of O2 at room temperature. However, the spark (i.e., Bunsen Burner) will cause it to burn and it continues to react. Electrolysis  the act of passing electrical current through H2O so that the molecule will decompose to H2 and O2. H2O doesn’t spontaneously decompose, so we have to add something (i.e., electricity) to make the rxn go. It requires a continuous source of energy for the rxn to occur (unlike the Bunsen burner). In the air H2 and O2 react, but it’s occurring at such a slow rate you don’t see it. When freezing energy coming in was not fast enough to compete with the endothermic rxn. Heat of transfer  energy transfers b/c of a difference in T. Standard Formation Enthalpies  enthalpy change for forming 1mol of a compound from its elements in most stable forms at a given T and 1 bar pressure. ΔG°<0, K>1 (product-favored) and ΔG°>0, K<1 (reactant-favored). K° is the equilibrium constant in which each value in the equilibrium constant expression is divided by the standard pressure or standard concentration. Entropy is related to probability. It more likely for energy to be dispersed then localized in an area. Entropy measures how many atoms can be arranged in a certain energy level. The more gas molecules present the bigger entropy will be. DEMO VIDEO: 2NO(g) + O2(g) 2NO2(g). Spontaneous when the two separate gases come into contact with one another. Energy is released into the surroundings (as more E spreads out, entropy increases). The surroundings warm up as temperature increases (exothermic rxn). Rules for if ΔG°>0: 1) Couple the nonspontaneous rxn toa spontaneous one (thermite rxn: Fe2O3(s)2Fe(s) + 3/2O2(g) coupled w/ 2Al(s)+3/2O2(g)Al2O3(s)). Cancel out repeats to get Fe2O3(s)+ 2Al(s)2Fe(s)+Al2O3(s). 2)Change the Temperature to make ΔG°<0 (DEMO: Corroded silver heat up to release the O2 (Ag2O(s)2Ag(s)+1/2O2(g)). For ΔG° that calculated at different temperatures, estimations can be made for ΔH and ΔS (ΔH1000K ≅ΔH25°C and the same goes for ΔS; only if the substances are in the same phase (s), (l), or (g)). If the phase changed then ΔH and ΔS would be different at those temperatures.Strong Acids: HCl, HBr, HI, HNO3, H2SO4, HClO4, and HClO3.Strong Bases: Group IA Hydroxides (LiOH, NaOH, KOH, RbOH, CsOH) and Group IIA Hydroxides (Ca(OH)2, Sr(OH)2, and Ba(OH)2 ONLY)Spectator Ions: Cl-, Br-, I-, NO3-, ClO3-, CIO4-, Li+, Na+, K+, Rb+, Cs+, Ca2+. Sr2+, Ba2+, etc. Water Ionization: KW = [H3O+][OH-] or KW = [H+][OH-] General Formula for Buffers: H+ + A-  HA and HA + OH-  A- + H2O (A- is the base and HA is the acid; H+ is the strong acid)Key word(s): “determine T, ΔH, or ΔS at which this rxn becomes spontaneous” means to make ΔG = 0. When determining the enthalpy change for a substance that has been dissolved in water/solvent always add the mass of water and the mass of the solute together! DO NOT, I repeat, DO NOT change Celsius to Kelvins in q = m x Cs x ΔT (just use Celsius b/c there’s no need to change to Kelvins)3 Types of Lewis Acids: 1) Electron deficient structures (i.e., BF3 +NH3); 2) Metal ions especially w/ high charges (Al3+, Fe3+); 3) Molecules w/ double bonds (non-metal oxides) (CO2 + H2O). Non-metal oxides are acidic and metal oxides are basic.Arrenhius Definition: Acids react w/ H2O to increase H3O+ ions and bases react w/ H2O to increase the OH- ions. Brønsted-Lowry: Acids donate H+, bases accept H+ (amphiprotic substances can act as acids or bases). Lewis Definition: acids are electron pair acceptors, bases are electron pair donors (describes metal complexes and why the metal complexes with water yield acidic solutions when dissolved in water,i.e., the Copper Chloride pink/blue lab). The stronger the acid the weaker its conjugate base is (vice-versa) Sulfuric Acid DEMO: (SO3 dissolves in water and reacts with water creating H2SO4 making acid rain. SO3 has an orbital to accept electrons so it’s Lewis acid and H2O is the Lewis base). Lewis acid/bases allow nonpolar substances to be able to dissolve in polar solns.ΔH ΔS Product-Favored?- + Always- - Low T, yesHigh T, no+ + High T, yesLow T, no+ -