CH 302 1st Edition Lecture 8 Outline of Last Lecture I. Quiz QuestionII. Freezing point and Henry’s LawIII. Solutions and solubilityOutline of Current Lecture I. Concept of Equilibrium ConcentrationsII. Law of Mass ActionIII. Equilibrium ConstantCurrent LectureConcept of Equilibrium Concentrations:1. Graph the change in concentration over time of:PbCl2(s) Pb2+(aq) + 2Cl-(aq)- Do not graph solids because they do not havea concentration- There is twice as much Cl- as Pb2+, so Cl-should have a higher concentration2. What is the equation for the following graphs?(a)Answer: N2 + 3 H2 2NH3(b)Answer: CO + H2O CO2 + H2O- [CO2] and [H2] are products- [CO] and [H2O] are reactants**At the end, there are still SOME reactants, but there are more products presentLaw of Mass Action:1. You are given 10 moles of H2 and 1 mole of N2. At equilibrium, there is 1 mole of NH3, how many moles of H2 are there?There are two ways of solving this problem:(a) Using stoichiometry:3 H2 (g) + N2 (g) 2NH3 (g)1 mol NH3 x 3 mol H2 = 1.5 H2 2 mol NH310 mol H2 (the given amount of moles) – 1.5 H2 = 8.5 moles H2(b) Using RICE tablesR 3 H2 (g) N2 (g) 2NH3 (g)I 10 moles 1 mole 0 molesC -3x -x +2xE 10-3x 1-x 2xSince we know that there is 1 mole of NH3 at equilibrium (from the problem given), we can set 2x = 1 (from the RICE table)2x = 1x = 0.5Now that we know what “x” is, we can plug this into “10-3x” to find out how many moles of H2 is at equilibrium10- 3(0.5) = 8.5 moles H2Equilibrium Constant:- K is the equilibrium constant where:o K = Products ReactantsSo given the equation jA + kB lC + mD, K = (C^l ) x (D^m) (A^j) x (B^k)- K > 1 means that there are more products than reactantso At equilibrium, products are favored- K < 1 means that there are more reactants than productso At equilibrium, reactants are favored- Equilibrium does not depend on starting
View Full Document
Unlocking...