USING K VALUES IN EQUILIBRIUM CALCULATIONS, Summaries of Chemistry

Download USING K VALUES IN EQUILIBRIUM CALCULATIONS and more Summaries Chemistry in PDF only on Docsity! USING K VALUES IN EQUILIBRIUM CALCULATIONS CH40S – UNIT 3 Equilibrium REVIEW When 0.800 moles of SO2 and 0.800 moles of O2 a 2.00 L container and allowed to reach equilibrium, the equilibrium [SO3] is to be 0.300 M. Calculate the Keq value. 2 SO2 (g) + O2 (g) ⇋ 2 SO3 (g) Working with K values 1.  What will the concentration of be at equilibrium? 2.  How can we determine this? INITIAL CONCENTRATIONS K = 25 @ this temp. + ⇋ + Working with K values INITIAL [NO2] I C E K = 25 @ this temp. + ⇋ + H2(g) + S(s) ⇄ H2S(g) Keq= 14 1.  0.80 moles of H2 and 1.4 moles of S are initially put in a 4.0 L flask and allowed to reach equilibrium. Calculate the [H2] at equilibrium. I 0.20 M 0 C -x +x E 0.20 - x x Keq = [H2S] [H2] x = 0.2 - x = 14 The Chemistry… Approximating 10 ¨  Sometimes, the math gets pretty hairy when you have an “x” involved. To simplify things, you can make the following assumption: ¨  If Keq is really small the reaction will not proceed to the right very far, meaning the equilibrium concentrations will be nearly the same as the initial concentrations of your reactants. 0.20 – x is just about 0.20 if x is really tiny. THE “100 RULE” If the [initial] is at least 100x bigger than the K value for the reaction, ignore x! Otherwise, you have to use the quadratic. Yay! I can ignore “x”! Carbon monoxide gas is a primary starting material in the synthesis of many organic compounds. At 2000oC, K = 6.40 x 10-7 for the decomposition of CO2. Calculate the equilibrium concentrations of all entities if 0.250 mol of CO2 is initially placed in a 1.000 L closed container at 2000oC. 2CO2(g) ⇄ 2CO(g) + O2(g) Arghh! I can’t ignore “x”! If 0.500 mol of N2O4(g) is placed in a 1.00 L closed container at 150oC, what will the equilibrium concentrations of all entities be? The equilibrium constant (K) for this reaction at these conditions is 4.50. N2O4(g) ⇄ 2NO2(g)