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 G 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 the act of passing electrical current through H2O so that Electrolysis 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 G 0 K 1 product favored and G 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 G 0 1 Couple the nonspontaneous rxn to a 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 G 0 DEMO Corroded silver heat up to release the O2 Ag2O s 2Ag s 1 2O2 g For G that calculated at different temperatures estimations can be made for H and S H1000K H25 C and the same goes for S only if the substances are in the same phase s l or g If the phase changed then H and S 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 Ca2 Sr2 Ba2 etc Water Ionization KW H3O OH or KW H OH ClO3 CIO4 Li Na K Rb Cs 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 H or S at which this rxn becomes spontaneous means to make G 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 T 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 Br nsted 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 H S Product Favored Always Low T yes High T no High T yes Low T no Never