<p> The Ch. 19. Day 1</p><p>- In the lab we see how different things change the reaction rate. Both temperature and concentration effect how quickly a reaction occurs. - We actually could make mathematical expressions of the reaction rate. - For the reaction aA + bB cC + dD the rate expression might be: Rate = k [A]a[B]b (if this reaction is one step) (Here things in [ ] are concentrations in molarity and k is a temperature dependent constant) - Here would be a great place for some tough mathematics on reaction rates … but we’re going to use this information to study equilibrium reactions. - Equilibrium reactions are reversible reactions - For an equation to be at equilibrium the rate of the forward reaction is equal to the rate of the reverse reaction.</p><p>- N2(g) + 3H2(g) ⇌ 2NH3(g)</p><p>What equilibrium does mean</p><p>What equilibrium doesn’t mean</p><p>- We derive an equilibrium expression - For the reaction aA + bB cC + dD</p><p>[C] c [D] d a b the equilibrium expression Keq = [A] [B]</p><p> brackets [] once again mean molarity a,b,c, and d came from the coefficients in the balanced equation to be included in the expression it must be a (g) or (aq) not a (s) or a (l) Now we can do lots and lots of incredibly fun problems!!!!!! 1) Write equilibrium expressions for the following reactions:</p><p>2SO3(g) ⇌ 2SO2(g) + O2(g)</p><p>4NH3(g) + 3O2(g) ⇌ 2N2(g) + 6H2O(l)</p><p>2) Hydrogen gas and carbon dioxide gas set up an equilibrium with carbon monoxide gas and water vapor. Calculate the value of the equilibrium constant, Kc , for the system, if 0.1908 moles of CO2, 0.0908 moles of H2, 0.0092 moles of CO, and 0.0092 moles of H2O vapor were present in a 2.00 L reaction vessel were present at equilibrium. </p><p>3) Given the balanced equation, the K value and the partial set of equilibrium concentrations shown: -2 CH3OH  CO + 2H2 K=1.59*10 Equilibrium Concentrations: CO = 0.105M, H2 = 0.212M What is the equilibrium concentration of CH3OH? The reaction quotient (Q) is used to determine if a reaction is at equilibrium, and if is not, which way the equilibrium must shift (side to favor) to reach equilibrium. - In these types of problems molarities of all the species in the equilibrium expression must be given. Also the value of K must be given. - Substitute the molarities into the equilibrium expression… the value you get is Q not K. - Then analyze: - If Q = K then the reaction is at equilibrium - If Q > K then the reaction must shift towards the left - If Q < K then the reaction must shift towards the right EX: More fun problems!</p><p>Example: 0.035 moles of SO2, 0.500 moles of SO2Cl2, and 0.080 moles of Cl2 are combined in an evacuated 5.00 L flask and heated to 100oC. What is Q before the reaction begins? Which direction will the reaction proceed in order to establish equilibrium? </p><p> o SO2Cl2(g) SO2(g) + Cl2(g) Kc = 0.078 at 100 C</p><p>- Le Chatlier’s Principle:</p><p>- Things that effect an equilibrium: - Concentration</p><p>- Pressure</p><p>- Heat </p><p>- Catalyst</p><p>Look one last time at the Haber process:</p><p>N2(g) + 3H2(g) ⇌ 2NH3(g) H = -92.4 kJ how could we increase the yield of ammonia? PROBLEM SET 19A</p><p>Write equilibrium expressions for the following reactions:</p><p> a) 2SO3(g) ⇌ 2SO2(g) + O2(g)</p><p> b) carbon and water vapor reach an equilibrium with carbon monoxide and hydrogen gases </p><p> c) 4NH3(g) + 3O2(g) ⇌ 2N2(g) + 6H2O(l)</p><p> d) dinitrogen tetroxide gas is in equilibrium with nitrogen dioxide gas</p><p> e) Fe3O4(s) reacts with hydrogen gas to form an equilibrium with solid iron and water vapor</p><p>1) What is the K of equation 1a) if at equilibrium [SO2] & [O2] = .020 M, and [SO3] = 1.46 M</p><p>2) At 600 C the K for equation 1c) is 80. What is the equilibrium concentration of ammonia if [O2] = 0.5 M, [N2] = 1.05 M, and there is 25 ml of water at equilibrium. </p><p>3) a) If the above equation had concentrations (not at equilibrium) of 1.0 M for all the relevant reactants and products which way would the equilibrium go to reach equilibrium.</p><p> b) What if all the relevant concentrations were 0.4 M?</p><p>4) If reaction 1c) had a H = -1530.4 kJ how would the following stresses shift the equilibrium (L-left, R- right, N-no effect) _____a) take away water _____b) adding water _____c) adding a catalyst _____d) cool the reaction _____e) increasing the pressure _____f) remove ammonia _____f) add nitrogen _____g) adding heat</p><p>5) The H for 1a) is 98.9 kJ. Name five ways to increase the amount of SO2 in the equilibrium. 1)______4)______2)______5)______3)______</p>