Chapter 14 15 Equilibrium Acids Bases Homogenous all equilibrium systems are in the same phase ex all in the gas phase Heterogenous 2 or more phases exist in the system o GASES ONLY CHANGE CONCENTRATION o The equilibrium constant ONLY contains gas phase species Concentration constant M Kc products reactants Kc Kc a x Kc b Ex aA bB cC dD Kc C c D d A a B b If you REVERSE the reaction Take the INVERSE of KC 1 Kc If you multiply by an exponent Take Kc to that POWER Kc 2 When Kc is very large it means there are NO REACTANTS so equation goes right When Kc is very small it means the equation goes towards the reactants Pressure Constant Kp Kc RT n when n 0 KC KP Reaction Quotient Qc or Qp not always at equilibrium Qc Kc system at equilibrium Qc Kc system shifts R forward direction too many reactants not enough products Qc Kc system shifts L reverse direction too many products not enough reactants When calculating equilibrium or concentrations ALWAYS compare Qc to Kc to determine whether the reactants or products increase Then set up the ice box and solve LeChatelier s Principle disturbing a system at equilibrium is possible by changing concentration of its components o When system moves left concentration of products decreases and reactants increases o ADDING SOLID DOES NOT CHANGE CONCENTRATION Endothermic heat is a reactant H 0 o temperature shifts right o temperature shifts left Exothermic heat is a product H 0 o temperature shifts left o temperature shifts right Pressure o Pressure shifts to side with less moles o Pressure shifts to side with more moles If mols reactants mols products there will be NO SHIFT Acid Base Conj Acid conj Base aq A aq HA aq H2O l H3O Acid always forms the conjugate base base always forms conjugate acid o Amphroteric acts as either a base or an acid ex H2O Strong acids bases form weak conj acids bases there concentrations are same as ions Weak acids bases form strong conj acids bases use ICE to find concentration Arrhenius Acids H donors Arrhenius Bases OH donors Bronstead Acids H donors Bronstead Bases H acceptors Neutral Solution H OH pH 7 Acidic Solution H 1 0 x 10 7 pH 7 Basic Solution H 1 0 x 10 7 pH 7 pH log H pOH log OH H 10 pH Be careful with sig figs numbers to the left of the decimal are NOT SIGNIFICANT H OH 1 0 x 10 14 therefore pH pOH 14 Set up the equilibrium constant of N2O4 2NO2 What is the equilibrium constant Kc given CH4 045M C2H2 035M and H2 105M Also what happens if you reverse the reaction What if you reverse the reaction and double it 2CH4 C2H2 3H2 If CH4 065M and C2H2 40M calculate H2 given Kc 020M 2CH4 C2H2 3H2 Set up the equilibrium concentration of the following CaCO3 s CaO s CO2 g What is Kp at 200 o C given that K c 44 in the following reaction H2 g I2 g 2HI g What is Kp at 1000K if Kc 3 8x10 3 in the following reaction CH 4 g H2O g CO g 3H2 g If H2 0 10M I2 0 20M HI 0 40M will the mixture shift if Kc 57 0 Calculate the concentrations at equilibrium given Kc 50 at 127 0 C N 2O4 2NO2 What is H2PO4 in the following reaction Calculate the H of a 0 020M proprionic acid CH 3CH2COOH give Ka 1 3x10 5 Calculate H in a 0 050M HF 4 aq solution given Ka 3 5x10 What is the pH of a H 5 0 x 10 4 Then solve for pOH Is the solution basic or acidic Calculate the H OH citrate in orange juice with a pH 2 85 Calculate the pH of a 0 20M NaOCl solution given pKa HClO 7 54 Calculate the pH of a 0 150M H2CO4 solution given Ka1 5 6 x 10 2 and K 5 a2 5 4 x 10 4 Calculate the pH of a 10M solution of formic acid given Ka 1 8 x 10